super.c

Go to the documentation of this file.

/*
 *  linux/fs/ext4/super.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/vmalloc.h>
#include <linux/jbd2.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/parser.h>
#include <linux/buffer_head.h>
#include <linux/exportfs.h>
#include <linux/vfs.h>
#include <linux/random.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/ctype.h>
#include <linux/log2.h>
#include <linux/crc16.h>
#include <linux/cleancache.h>
#include <asm/uaccess.h>

#include <linux/kthread.h>
#include <linux/freezer.h>

#include "ext4.h"
#include "ext4_extents.h"
#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"
#include "mballoc.h"

#define CREATE_TRACE_POINTS
#include <trace/events/ext4.h>

static struct proc_dir_entry *ext4_proc_root;
static struct kset *ext4_kset;
static struct ext4_lazy_init *ext4_li_info;
static struct mutex ext4_li_mtx;
static struct ext4_features *ext4_feat;

static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
                 unsigned long journal_devnum);
static int ext4_show_options(struct seq_file *seq, struct dentry *root);
static int ext4_commit_super(struct super_block *sb, int sync);
static void ext4_mark_recovery_complete(struct super_block *sb,
                    struct ext4_super_block *es);
static void ext4_clear_journal_err(struct super_block *sb,
                   struct ext4_super_block *es);
static int ext4_sync_fs(struct super_block *sb, int wait);
static const char *ext4_decode_error(struct super_block *sb, int errno,
                     char nbuf[16]);
static int ext4_remount(struct super_block *sb, int *flags, char *data);
static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf);
static int ext4_unfreeze(struct super_block *sb);
static int ext4_freeze(struct super_block *sb);
static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags,
               const char *dev_name, void *data);
static inline int ext2_feature_set_ok(struct super_block *sb);
static inline int ext3_feature_set_ok(struct super_block *sb);
static int ext4_feature_set_ok(struct super_block *sb, int readonly);
static void ext4_destroy_lazyinit_thread(void);
static void ext4_unregister_li_request(struct super_block *sb);
static void ext4_clear_request_list(void);

#if !defined(CONFIG_EXT2_FS) && !defined(CONFIG_EXT2_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
static struct file_system_type ext2_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "ext2",
    .mount      = ext4_mount,
    .kill_sb    = kill_block_super,
    .fs_flags   = FS_REQUIRES_DEV,
};
#define IS_EXT2_SB(sb) ((sb)->s_bdev->bd_holder == &ext2_fs_type)
#else
#define IS_EXT2_SB(sb) (0)
#endif


#if !defined(CONFIG_EXT3_FS) && !defined(CONFIG_EXT3_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
static struct file_system_type ext3_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "ext3",
    .mount      = ext4_mount,
    .kill_sb    = kill_block_super,
    .fs_flags   = FS_REQUIRES_DEV,
};
#define IS_EXT3_SB(sb) ((sb)->s_bdev->bd_holder == &ext3_fs_type)
#else
#define IS_EXT3_SB(sb) (0)
#endif

static int ext4_verify_csum_type(struct super_block *sb,
                 struct ext4_super_block *es)
{
    if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return 1;

    return es->s_checksum_type == EXT4_CRC32C_CHKSUM;
}

static __le32 ext4_superblock_csum(struct super_block *sb,
                   struct ext4_super_block *es)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    int offset = offsetof(struct ext4_super_block, s_checksum);
    __u32 csum;

    csum = ext4_chksum(sbi, ~0, (char *)es, offset);

    return cpu_to_le32(csum);
}

int ext4_superblock_csum_verify(struct super_block *sb,
                struct ext4_super_block *es)
{
    if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return 1;

    return es->s_checksum == ext4_superblock_csum(sb, es);
}

void ext4_superblock_csum_set(struct super_block *sb)
{
    struct ext4_super_block *es = EXT4_SB(sb)->s_es;

    if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return;

    es->s_checksum = ext4_superblock_csum(sb, es);
}

void *ext4_kvmalloc(size_t size, gfp_t flags)
{
    void *ret;

    ret = kmalloc(size, flags);
    if (!ret)
        ret = __vmalloc(size, flags, PAGE_KERNEL);
    return ret;
}

void *ext4_kvzalloc(size_t size, gfp_t flags)
{
    void *ret;

    ret = kzalloc(size, flags);
    if (!ret)
        ret = __vmalloc(size, flags | __GFP_ZERO, PAGE_KERNEL);
    return ret;
}

void ext4_kvfree(void *ptr)
{
    if (is_vmalloc_addr(ptr))
        vfree(ptr);
    else
        kfree(ptr);

}

ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,
                   struct ext4_group_desc *bg)
{
    return le32_to_cpu(bg->bg_block_bitmap_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (ext4_fsblk_t)le32_to_cpu(bg->bg_block_bitmap_hi) << 32 : 0);
}

ext4_fsblk_t ext4_inode_bitmap(struct super_block *sb,
                   struct ext4_group_desc *bg)
{
    return le32_to_cpu(bg->bg_inode_bitmap_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (ext4_fsblk_t)le32_to_cpu(bg->bg_inode_bitmap_hi) << 32 : 0);
}

ext4_fsblk_t ext4_inode_table(struct super_block *sb,
                  struct ext4_group_desc *bg)
{
    return le32_to_cpu(bg->bg_inode_table_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (ext4_fsblk_t)le32_to_cpu(bg->bg_inode_table_hi) << 32 : 0);
}

__u32 ext4_free_group_clusters(struct super_block *sb,
                   struct ext4_group_desc *bg)
{
    return le16_to_cpu(bg->bg_free_blocks_count_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (__u32)le16_to_cpu(bg->bg_free_blocks_count_hi) << 16 : 0);
}

__u32 ext4_free_inodes_count(struct super_block *sb,
                  struct ext4_group_desc *bg)
{
    return le16_to_cpu(bg->bg_free_inodes_count_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (__u32)le16_to_cpu(bg->bg_free_inodes_count_hi) << 16 : 0);
}

__u32 ext4_used_dirs_count(struct super_block *sb,
                  struct ext4_group_desc *bg)
{
    return le16_to_cpu(bg->bg_used_dirs_count_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (__u32)le16_to_cpu(bg->bg_used_dirs_count_hi) << 16 : 0);
}

__u32 ext4_itable_unused_count(struct super_block *sb,
                  struct ext4_group_desc *bg)
{
    return le16_to_cpu(bg->bg_itable_unused_lo) |
        (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
         (__u32)le16_to_cpu(bg->bg_itable_unused_hi) << 16 : 0);
}

void ext4_block_bitmap_set(struct super_block *sb,
               struct ext4_group_desc *bg, ext4_fsblk_t blk)
{
    bg->bg_block_bitmap_lo = cpu_to_le32((u32)blk);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_block_bitmap_hi = cpu_to_le32(blk >> 32);
}

void ext4_inode_bitmap_set(struct super_block *sb,
               struct ext4_group_desc *bg, ext4_fsblk_t blk)
{
    bg->bg_inode_bitmap_lo  = cpu_to_le32((u32)blk);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_inode_bitmap_hi = cpu_to_le32(blk >> 32);
}

void ext4_inode_table_set(struct super_block *sb,
              struct ext4_group_desc *bg, ext4_fsblk_t blk)
{
    bg->bg_inode_table_lo = cpu_to_le32((u32)blk);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_inode_table_hi = cpu_to_le32(blk >> 32);
}

void ext4_free_group_clusters_set(struct super_block *sb,
                  struct ext4_group_desc *bg, __u32 count)
{
    bg->bg_free_blocks_count_lo = cpu_to_le16((__u16)count);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_free_blocks_count_hi = cpu_to_le16(count >> 16);
}

void ext4_free_inodes_set(struct super_block *sb,
              struct ext4_group_desc *bg, __u32 count)
{
    bg->bg_free_inodes_count_lo = cpu_to_le16((__u16)count);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_free_inodes_count_hi = cpu_to_le16(count >> 16);
}

void ext4_used_dirs_set(struct super_block *sb,
              struct ext4_group_desc *bg, __u32 count)
{
    bg->bg_used_dirs_count_lo = cpu_to_le16((__u16)count);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_used_dirs_count_hi = cpu_to_le16(count >> 16);
}

void ext4_itable_unused_set(struct super_block *sb,
              struct ext4_group_desc *bg, __u32 count)
{
    bg->bg_itable_unused_lo = cpu_to_le16((__u16)count);
    if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
        bg->bg_itable_unused_hi = cpu_to_le16(count >> 16);
}


/* Just increment the non-pointer handle value */
static handle_t *ext4_get_nojournal(void)
{
    handle_t *handle = current->journal_info;
    unsigned long ref_cnt = (unsigned long)handle;

    BUG_ON(ref_cnt >= EXT4_NOJOURNAL_MAX_REF_COUNT);

    ref_cnt++;
    handle = (handle_t *)ref_cnt;

    current->journal_info = handle;
    return handle;
}


/* Decrement the non-pointer handle value */
static void ext4_put_nojournal(handle_t *handle)
{
    unsigned long ref_cnt = (unsigned long)handle;

    BUG_ON(ref_cnt == 0);

    ref_cnt--;
    handle = (handle_t *)ref_cnt;

    current->journal_info = handle;
}

/*
 * Wrappers for jbd2_journal_start/end.
 */
handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks)
{
    journal_t *journal;

    trace_ext4_journal_start(sb, nblocks, _RET_IP_);
    if (sb->s_flags & MS_RDONLY)
        return ERR_PTR(-EROFS);

    WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
    journal = EXT4_SB(sb)->s_journal;
    if (!journal)
        return ext4_get_nojournal();
    /*
     * Special case here: if the journal has aborted behind our
     * backs (eg. EIO in the commit thread), then we still need to
     * take the FS itself readonly cleanly.
     */
    if (is_journal_aborted(journal)) {
        ext4_abort(sb, "Detected aborted journal");
        return ERR_PTR(-EROFS);
    }
    return jbd2_journal_start(journal, nblocks);
}

int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle)
{
    struct super_block *sb;
    int err;
    int rc;

    if (!ext4_handle_valid(handle)) {
        ext4_put_nojournal(handle);
        return 0;
    }
    sb = handle->h_transaction->t_journal->j_private;
    err = handle->h_err;
    rc = jbd2_journal_stop(handle);

    if (!err)
        err = rc;
    if (err)
        __ext4_std_error(sb, where, line, err);
    return err;
}

void ext4_journal_abort_handle(const char *caller, unsigned int line,
                   const char *err_fn, struct buffer_head *bh,
                   handle_t *handle, int err)
{
    char nbuf[16];
    const char *errstr = ext4_decode_error(NULL, err, nbuf);

    BUG_ON(!ext4_handle_valid(handle));

    if (bh)
        BUFFER_TRACE(bh, "abort");

    if (!handle->h_err)
        handle->h_err = err;

    if (is_handle_aborted(handle))
        return;

    printk(KERN_ERR "EXT4-fs: %s:%d: aborting transaction: %s in %s\n",
           caller, line, errstr, err_fn);

    jbd2_journal_abort_handle(handle);
}

static void __save_error_info(struct super_block *sb, const char *func,
                unsigned int line)
{
    struct ext4_super_block *es = EXT4_SB(sb)->s_es;

    EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
    es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
    es->s_last_error_time = cpu_to_le32(get_seconds());
    strncpy(es->s_last_error_func, func, sizeof(es->s_last_error_func));
    es->s_last_error_line = cpu_to_le32(line);
    if (!es->s_first_error_time) {
        es->s_first_error_time = es->s_last_error_time;
        strncpy(es->s_first_error_func, func,
            sizeof(es->s_first_error_func));
        es->s_first_error_line = cpu_to_le32(line);
        es->s_first_error_ino = es->s_last_error_ino;
        es->s_first_error_block = es->s_last_error_block;
    }
    /*
     * Start the daily error reporting function if it hasn't been
     * started already
     */
    if (!es->s_error_count)
        mod_timer(&EXT4_SB(sb)->s_err_report, jiffies + 24*60*60*HZ);
    le32_add_cpu(&es->s_error_count, 1);
}

static void save_error_info(struct super_block *sb, const char *func,
                unsigned int line)
{
    __save_error_info(sb, func, line);
    ext4_commit_super(sb, 1);
}

/*
 * The del_gendisk() function uninitializes the disk-specific data
 * structures, including the bdi structure, without telling anyone
 * else.  Once this happens, any attempt to call mark_buffer_dirty()
 * (for example, by ext4_commit_super), will cause a kernel OOPS.
 * This is a kludge to prevent these oops until we can put in a proper
 * hook in del_gendisk() to inform the VFS and file system layers.
 */
static int block_device_ejected(struct super_block *sb)
{
    struct inode *bd_inode = sb->s_bdev->bd_inode;
    struct backing_dev_info *bdi = bd_inode->i_mapping->backing_dev_info;

    return bdi->dev == NULL;
}

static void ext4_journal_commit_callback(journal_t *journal, transaction_t *txn)
{
    struct super_block      *sb = journal->j_private;
    struct ext4_sb_info     *sbi = EXT4_SB(sb);
    int             error = is_journal_aborted(journal);
    struct ext4_journal_cb_entry    *jce, *tmp;

    spin_lock(&sbi->s_md_lock);
    list_for_each_entry_safe(jce, tmp, &txn->t_private_list, jce_list) {
        list_del_init(&jce->jce_list);
        spin_unlock(&sbi->s_md_lock);
        jce->jce_func(sb, jce, error);
        spin_lock(&sbi->s_md_lock);
    }
    spin_unlock(&sbi->s_md_lock);
}

/* Deal with the reporting of failure conditions on a filesystem such as
 * inconsistencies detected or read IO failures.
 *
 * On ext2, we can store the error state of the filesystem in the
 * superblock.  That is not possible on ext4, because we may have other
 * write ordering constraints on the superblock which prevent us from
 * writing it out straight away; and given that the journal is about to
 * be aborted, we can't rely on the current, or future, transactions to
 * write out the superblock safely.
 *
 * We'll just use the jbd2_journal_abort() error code to record an error in
 * the journal instead.  On recovery, the journal will complain about
 * that error until we've noted it down and cleared it.
 */

static void ext4_handle_error(struct super_block *sb)
{
    if (sb->s_flags & MS_RDONLY)
        return;

    if (!test_opt(sb, ERRORS_CONT)) {
        journal_t *journal = EXT4_SB(sb)->s_journal;

        EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED;
        if (journal)
            jbd2_journal_abort(journal, -EIO);
    }
    if (test_opt(sb, ERRORS_RO)) {
        ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
        sb->s_flags |= MS_RDONLY;
    }
    if (test_opt(sb, ERRORS_PANIC))
        panic("EXT4-fs (device %s): panic forced after error\n",
            sb->s_id);
}

void __ext4_error(struct super_block *sb, const char *function,
          unsigned int line, const char *fmt, ...)
{
    struct va_format vaf;
    va_list args;

    va_start(args, fmt);
    vaf.fmt = fmt;
    vaf.va = &args;
    printk(KERN_CRIT "EXT4-fs error (device %s): %s:%d: comm %s: %pV\n",
           sb->s_id, function, line, current->comm, &vaf);
    va_end(args);
    save_error_info(sb, function, line);

    ext4_handle_error(sb);
}

void ext4_error_inode(struct inode *inode, const char *function,
              unsigned int line, ext4_fsblk_t block,
              const char *fmt, ...)
{
    va_list args;
    struct va_format vaf;
    struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;

    es->s_last_error_ino = cpu_to_le32(inode->i_ino);
    es->s_last_error_block = cpu_to_le64(block);
    save_error_info(inode->i_sb, function, line);
    va_start(args, fmt);
    vaf.fmt = fmt;
    vaf.va = &args;
    if (block)
        printk(KERN_CRIT "EXT4-fs error (device %s): %s:%d: "
               "inode #%lu: block %llu: comm %s: %pV\n",
               inode->i_sb->s_id, function, line, inode->i_ino,
               block, current->comm, &vaf);
    else
        printk(KERN_CRIT "EXT4-fs error (device %s): %s:%d: "
               "inode #%lu: comm %s: %pV\n",
               inode->i_sb->s_id, function, line, inode->i_ino,
               current->comm, &vaf);
    va_end(args);

    ext4_handle_error(inode->i_sb);
}

void ext4_error_file(struct file *file, const char *function,
             unsigned int line, ext4_fsblk_t block,
             const char *fmt, ...)
{
    va_list args;
    struct va_format vaf;
    struct ext4_super_block *es;
    struct inode *inode = file->f_dentry->d_inode;
    char pathname[80], *path;

    es = EXT4_SB(inode->i_sb)->s_es;
    es->s_last_error_ino = cpu_to_le32(inode->i_ino);
    save_error_info(inode->i_sb, function, line);
    path = d_path(&(file->f_path), pathname, sizeof(pathname));
    if (IS_ERR(path))
        path = "(unknown)";
    va_start(args, fmt);
    vaf.fmt = fmt;
    vaf.va = &args;
    if (block)
        printk(KERN_CRIT
               "EXT4-fs error (device %s): %s:%d: inode #%lu: "
               "block %llu: comm %s: path %s: %pV\n",
               inode->i_sb->s_id, function, line, inode->i_ino,
               block, current->comm, path, &vaf);
    else
        printk(KERN_CRIT
               "EXT4-fs error (device %s): %s:%d: inode #%lu: "
               "comm %s: path %s: %pV\n",
               inode->i_sb->s_id, function, line, inode->i_ino,
               current->comm, path, &vaf);
    va_end(args);

    ext4_handle_error(inode->i_sb);
}

static const char *ext4_decode_error(struct super_block *sb, int errno,
                     char nbuf[16])
{
    char *errstr = NULL;

    switch (errno) {
    case -EIO:
        errstr = "IO failure";
        break;
    case -ENOMEM:
        errstr = "Out of memory";
        break;
    case -EROFS:
        if (!sb || (EXT4_SB(sb)->s_journal &&
                EXT4_SB(sb)->s_journal->j_flags & JBD2_ABORT))
            errstr = "Journal has aborted";
        else
            errstr = "Readonly filesystem";
        break;
    default:
        /* If the caller passed in an extra buffer for unknown
         * errors, textualise them now.  Else we just return
         * NULL. */
        if (nbuf) {
            /* Check for truncated error codes... */
            if (snprintf(nbuf, 16, "error %d", -errno) >= 0)
                errstr = nbuf;
        }
        break;
    }

    return errstr;
}

/* __ext4_std_error decodes expected errors from journaling functions
 * automatically and invokes the appropriate error response.  */

void __ext4_std_error(struct super_block *sb, const char *function,
              unsigned int line, int errno)
{
    char nbuf[16];
    const char *errstr;

    /* Special case: if the error is EROFS, and we're not already
     * inside a transaction, then there's really no point in logging
     * an error. */
    if (errno == -EROFS && journal_current_handle() == NULL &&
        (sb->s_flags & MS_RDONLY))
        return;

    errstr = ext4_decode_error(sb, errno, nbuf);
    printk(KERN_CRIT "EXT4-fs error (device %s) in %s:%d: %s\n",
           sb->s_id, function, line, errstr);
    save_error_info(sb, function, line);

    ext4_handle_error(sb);
}

/*
 * ext4_abort is a much stronger failure handler than ext4_error.  The
 * abort function may be used to deal with unrecoverable failures such
 * as journal IO errors or ENOMEM at a critical moment in log management.
 *
 * We unconditionally force the filesystem into an ABORT|READONLY state,
 * unless the error response on the fs has been set to panic in which
 * case we take the easy way out and panic immediately.
 */

void __ext4_abort(struct super_block *sb, const char *function,
        unsigned int line, const char *fmt, ...)
{
    va_list args;

    save_error_info(sb, function, line);
    va_start(args, fmt);
    printk(KERN_CRIT "EXT4-fs error (device %s): %s:%d: ", sb->s_id,
           function, line);
    vprintk(fmt, args);
    printk("\n");
    va_end(args);

    if ((sb->s_flags & MS_RDONLY) == 0) {
        ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
        sb->s_flags |= MS_RDONLY;
        EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED;
        if (EXT4_SB(sb)->s_journal)
            jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
        save_error_info(sb, function, line);
    }
    if (test_opt(sb, ERRORS_PANIC))
        panic("EXT4-fs panic from previous error\n");
}

void ext4_msg(struct super_block *sb, const char *prefix, const char *fmt, ...)
{
    struct va_format vaf;
    va_list args;

    va_start(args, fmt);
    vaf.fmt = fmt;
    vaf.va = &args;
    printk("%sEXT4-fs (%s): %pV\n", prefix, sb->s_id, &vaf);
    va_end(args);
}

void __ext4_warning(struct super_block *sb, const char *function,
            unsigned int line, const char *fmt, ...)
{
    struct va_format vaf;
    va_list args;

    va_start(args, fmt);
    vaf.fmt = fmt;
    vaf.va = &args;
    printk(KERN_WARNING "EXT4-fs warning (device %s): %s:%d: %pV\n",
           sb->s_id, function, line, &vaf);
    va_end(args);
}

void __ext4_grp_locked_error(const char *function, unsigned int line,
                 struct super_block *sb, ext4_group_t grp,
                 unsigned long ino, ext4_fsblk_t block,
                 const char *fmt, ...)
__releases(bitlock)
__acquires(bitlock)
{
    struct va_format vaf;
    va_list args;
    struct ext4_super_block *es = EXT4_SB(sb)->s_es;

    es->s_last_error_ino = cpu_to_le32(ino);
    es->s_last_error_block = cpu_to_le64(block);
    __save_error_info(sb, function, line);

    va_start(args, fmt);

    vaf.fmt = fmt;
    vaf.va = &args;
    printk(KERN_CRIT "EXT4-fs error (device %s): %s:%d: group %u, ",
           sb->s_id, function, line, grp);
    if (ino)
        printk(KERN_CONT "inode %lu: ", ino);
    if (block)
        printk(KERN_CONT "block %llu:", (unsigned long long) block);
    printk(KERN_CONT "%pV\n", &vaf);
    va_end(args);

    if (test_opt(sb, ERRORS_CONT)) {
        ext4_commit_super(sb, 0);
        return;
    }

    ext4_unlock_group(sb, grp);
    ext4_handle_error(sb);
    /*
     * We only get here in the ERRORS_RO case; relocking the group
     * may be dangerous, but nothing bad will happen since the
     * filesystem will have already been marked read/only and the
     * journal has been aborted.  We return 1 as a hint to callers
     * who might what to use the return value from
     * ext4_grp_locked_error() to distinguish between the
     * ERRORS_CONT and ERRORS_RO case, and perhaps return more
     * aggressively from the ext4 function in question, with a
     * more appropriate error code.
     */
    ext4_lock_group(sb, grp);
    return;
}

void ext4_update_dynamic_rev(struct super_block *sb)
{
    struct ext4_super_block *es = EXT4_SB(sb)->s_es;

    if (le32_to_cpu(es->s_rev_level) > EXT4_GOOD_OLD_REV)
        return;

    ext4_warning(sb,
             "updating to rev %d because of new feature flag, "
             "running e2fsck is recommended",
             EXT4_DYNAMIC_REV);

    es->s_first_ino = cpu_to_le32(EXT4_GOOD_OLD_FIRST_INO);
    es->s_inode_size = cpu_to_le16(EXT4_GOOD_OLD_INODE_SIZE);
    es->s_rev_level = cpu_to_le32(EXT4_DYNAMIC_REV);
    /* leave es->s_feature_*compat flags alone */
    /* es->s_uuid will be set by e2fsck if empty */

    /*
     * The rest of the superblock fields should be zero, and if not it
     * means they are likely already in use, so leave them alone.  We
     * can leave it up to e2fsck to clean up any inconsistencies there.
     */
}

/*
 * Open the external journal device
 */
static struct block_device *ext4_blkdev_get(dev_t dev, struct super_block *sb)
{
    struct block_device *bdev;
    char b[BDEVNAME_SIZE];

    bdev = blkdev_get_by_dev(dev, FMODE_READ|FMODE_WRITE|FMODE_EXCL, sb);
    if (IS_ERR(bdev))
        goto fail;
    return bdev;

fail:
    ext4_msg(sb, KERN_ERR, "failed to open journal device %s: %ld",
            __bdevname(dev, b), PTR_ERR(bdev));
    return NULL;
}

/*
 * Release the journal device
 */
static int ext4_blkdev_put(struct block_device *bdev)
{
    return blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
}

static int ext4_blkdev_remove(struct ext4_sb_info *sbi)
{
    struct block_device *bdev;
    int ret = -ENODEV;

    bdev = sbi->journal_bdev;
    if (bdev) {
        ret = ext4_blkdev_put(bdev);
        sbi->journal_bdev = NULL;
    }
    return ret;
}

static inline struct inode *orphan_list_entry(struct list_head *l)
{
    return &list_entry(l, struct ext4_inode_info, i_orphan)->vfs_inode;
}

static void dump_orphan_list(struct super_block *sb, struct ext4_sb_info *sbi)
{
    struct list_head *l;

    ext4_msg(sb, KERN_ERR, "sb orphan head is %d",
         le32_to_cpu(sbi->s_es->s_last_orphan));

    printk(KERN_ERR "sb_info orphan list:\n");
    list_for_each(l, &sbi->s_orphan) {
        struct inode *inode = orphan_list_entry(l);
        printk(KERN_ERR "  "
               "inode %s:%lu at %p: mode %o, nlink %d, next %d\n",
               inode->i_sb->s_id, inode->i_ino, inode,
               inode->i_mode, inode->i_nlink,
               NEXT_ORPHAN(inode));
    }
}

static void ext4_put_super(struct super_block *sb)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_super_block *es = sbi->s_es;
    int i, err;

    ext4_unregister_li_request(sb);
    dquot_disable(sb, -1, DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);

    flush_workqueue(sbi->dio_unwritten_wq);
    destroy_workqueue(sbi->dio_unwritten_wq);

    if (sbi->s_journal) {
        err = jbd2_journal_destroy(sbi->s_journal);
        sbi->s_journal = NULL;
        if (err < 0)
            ext4_abort(sb, "Couldn't clean up the journal");
    }

    del_timer(&sbi->s_err_report);
    ext4_release_system_zone(sb);
    ext4_mb_release(sb);
    ext4_ext_release(sb);
    ext4_xattr_put_super(sb);

    if (!(sb->s_flags & MS_RDONLY)) {
        EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
        es->s_state = cpu_to_le16(sbi->s_mount_state);
    }
    if (!(sb->s_flags & MS_RDONLY))
        ext4_commit_super(sb, 1);

    if (sbi->s_proc) {
        remove_proc_entry("options", sbi->s_proc);
        remove_proc_entry(sb->s_id, ext4_proc_root);
    }
    kobject_del(&sbi->s_kobj);

    for (i = 0; i < sbi->s_gdb_count; i++)
        brelse(sbi->s_group_desc[i]);
    ext4_kvfree(sbi->s_group_desc);
    ext4_kvfree(sbi->s_flex_groups);
    percpu_counter_destroy(&sbi->s_freeclusters_counter);
    percpu_counter_destroy(&sbi->s_freeinodes_counter);
    percpu_counter_destroy(&sbi->s_dirs_counter);
    percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
    brelse(sbi->s_sbh);
#ifdef CONFIG_QUOTA
    for (i = 0; i < MAXQUOTAS; i++)
        kfree(sbi->s_qf_names[i]);
#endif

    /* Debugging code just in case the in-memory inode orphan list
     * isn't empty.  The on-disk one can be non-empty if we've
     * detected an error and taken the fs readonly, but the
     * in-memory list had better be clean by this point. */
    if (!list_empty(&sbi->s_orphan))
        dump_orphan_list(sb, sbi);
    J_ASSERT(list_empty(&sbi->s_orphan));

    invalidate_bdev(sb->s_bdev);
    if (sbi->journal_bdev && sbi->journal_bdev != sb->s_bdev) {
        /*
         * Invalidate the journal device's buffers.  We don't want them
         * floating about in memory - the physical journal device may
         * hotswapped, and it breaks the `ro-after' testing code.
         */
        sync_blockdev(sbi->journal_bdev);
        invalidate_bdev(sbi->journal_bdev);
        ext4_blkdev_remove(sbi);
    }
    if (sbi->s_mmp_tsk)
        kthread_stop(sbi->s_mmp_tsk);
    sb->s_fs_info = NULL;
    /*
     * Now that we are completely done shutting down the
     * superblock, we need to actually destroy the kobject.
     */
    kobject_put(&sbi->s_kobj);
    wait_for_completion(&sbi->s_kobj_unregister);
    if (sbi->s_chksum_driver)
        crypto_free_shash(sbi->s_chksum_driver);
    kfree(sbi->s_blockgroup_lock);
    kfree(sbi);
}

static struct kmem_cache *ext4_inode_cachep;

/*
 * Called inside transaction, so use GFP_NOFS
 */
static struct inode *ext4_alloc_inode(struct super_block *sb)
{
    struct ext4_inode_info *ei;

    ei = kmem_cache_alloc(ext4_inode_cachep, GFP_NOFS);
    if (!ei)
        return NULL;

    ei->vfs_inode.i_version = 1;
    ei->vfs_inode.i_data.writeback_index = 0;
    memset(&ei->i_cached_extent, 0, sizeof(struct ext4_ext_cache));
    INIT_LIST_HEAD(&ei->i_prealloc_list);
    spin_lock_init(&ei->i_prealloc_lock);
    ei->i_reserved_data_blocks = 0;
    ei->i_reserved_meta_blocks = 0;
    ei->i_allocated_meta_blocks = 0;
    ei->i_da_metadata_calc_len = 0;
    ei->i_da_metadata_calc_last_lblock = 0;
    spin_lock_init(&(ei->i_block_reservation_lock));
#ifdef CONFIG_QUOTA
    ei->i_reserved_quota = 0;
#endif
    ei->jinode = NULL;
    INIT_LIST_HEAD(&ei->i_completed_io_list);
    spin_lock_init(&ei->i_completed_io_lock);
    ei->i_sync_tid = 0;
    ei->i_datasync_tid = 0;
    atomic_set(&ei->i_ioend_count, 0);
    atomic_set(&ei->i_unwritten, 0);

    return &ei->vfs_inode;
}

static int ext4_drop_inode(struct inode *inode)
{
    int drop = generic_drop_inode(inode);

    trace_ext4_drop_inode(inode, drop);
    return drop;
}

static void ext4_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(ext4_inode_cachep, EXT4_I(inode));
}

static void ext4_destroy_inode(struct inode *inode)
{
    if (!list_empty(&(EXT4_I(inode)->i_orphan))) {
        ext4_msg(inode->i_sb, KERN_ERR,
             "Inode %lu (%p): orphan list check failed!",
             inode->i_ino, EXT4_I(inode));
        print_hex_dump(KERN_INFO, "", DUMP_PREFIX_ADDRESS, 16, 4,
                EXT4_I(inode), sizeof(struct ext4_inode_info),
                true);
        dump_stack();
    }
    call_rcu(&inode->i_rcu, ext4_i_callback);
}

static void init_once(void *foo)
{
    struct ext4_inode_info *ei = (struct ext4_inode_info *) foo;

    INIT_LIST_HEAD(&ei->i_orphan);
#ifdef CONFIG_EXT4_FS_XATTR
    init_rwsem(&ei->xattr_sem);
#endif
    init_rwsem(&ei->i_data_sem);
    inode_init_once(&ei->vfs_inode);
}

static int init_inodecache(void)
{
    ext4_inode_cachep = kmem_cache_create("ext4_inode_cache",
                         sizeof(struct ext4_inode_info),
                         0, (SLAB_RECLAIM_ACCOUNT|
                        SLAB_MEM_SPREAD),
                         init_once);
    if (ext4_inode_cachep == NULL)
        return -ENOMEM;
    return 0;
}

static void destroy_inodecache(void)
{
    /*
     * Make sure all delayed rcu free inodes are flushed before we
     * destroy cache.
     */
    rcu_barrier();
    kmem_cache_destroy(ext4_inode_cachep);
}

void ext4_clear_inode(struct inode *inode)
{
    invalidate_inode_buffers(inode);
    clear_inode(inode);
    dquot_drop(inode);
    ext4_discard_preallocations(inode);
    if (EXT4_I(inode)->jinode) {
        jbd2_journal_release_jbd_inode(EXT4_JOURNAL(inode),
                           EXT4_I(inode)->jinode);
        jbd2_free_inode(EXT4_I(inode)->jinode);
        EXT4_I(inode)->jinode = NULL;
    }
}

static struct inode *ext4_nfs_get_inode(struct super_block *sb,
                    u64 ino, u32 generation)
{
    struct inode *inode;

    if (ino < EXT4_FIRST_INO(sb) && ino != EXT4_ROOT_INO)
        return ERR_PTR(-ESTALE);
    if (ino > le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))
        return ERR_PTR(-ESTALE);

    /* iget isn't really right if the inode is currently unallocated!!
     *
     * ext4_read_inode will return a bad_inode if the inode had been
     * deleted, so we should be safe.
     *
     * Currently we don't know the generation for parent directory, so
     * a generation of 0 means "accept any"
     */
    inode = ext4_iget(sb, ino);
    if (IS_ERR(inode))
        return ERR_CAST(inode);
    if (generation && inode->i_generation != generation) {
        iput(inode);
        return ERR_PTR(-ESTALE);
    }

    return inode;
}

static struct dentry *ext4_fh_to_dentry(struct super_block *sb, struct fid *fid,
                    int fh_len, int fh_type)
{
    return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
                    ext4_nfs_get_inode);
}

static struct dentry *ext4_fh_to_parent(struct super_block *sb, struct fid *fid,
                    int fh_len, int fh_type)
{
    return generic_fh_to_parent(sb, fid, fh_len, fh_type,
                    ext4_nfs_get_inode);
}

/*
 * Try to release metadata pages (indirect blocks, directories) which are
 * mapped via the block device.  Since these pages could have journal heads
 * which would prevent try_to_free_buffers() from freeing them, we must use
 * jbd2 layer's try_to_free_buffers() function to release them.
 */
static int bdev_try_to_free_page(struct super_block *sb, struct page *page,
                 gfp_t wait)
{
    journal_t *journal = EXT4_SB(sb)->s_journal;

    WARN_ON(PageChecked(page));
    if (!page_has_buffers(page))
        return 0;
    if (journal)
        return jbd2_journal_try_to_free_buffers(journal, page,
                            wait & ~__GFP_WAIT);
    return try_to_free_buffers(page);
}

#ifdef CONFIG_QUOTA
#define QTYPE2NAME(t) ((t) == USRQUOTA ? "user" : "group")
#define QTYPE2MOPT(on, t) ((t) == USRQUOTA?((on)##USRJQUOTA):((on)##GRPJQUOTA))

static int ext4_write_dquot(struct dquot *dquot);
static int ext4_acquire_dquot(struct dquot *dquot);
static int ext4_release_dquot(struct dquot *dquot);
static int ext4_mark_dquot_dirty(struct dquot *dquot);
static int ext4_write_info(struct super_block *sb, int type);
static int ext4_quota_on(struct super_block *sb, int type, int format_id,
             struct path *path);
static int ext4_quota_on_sysfile(struct super_block *sb, int type,
                 int format_id);
static int ext4_quota_off(struct super_block *sb, int type);
static int ext4_quota_off_sysfile(struct super_block *sb, int type);
static int ext4_quota_on_mount(struct super_block *sb, int type);
static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data,
                   size_t len, loff_t off);
static ssize_t ext4_quota_write(struct super_block *sb, int type,
                const char *data, size_t len, loff_t off);
static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
                 unsigned int flags);
static int ext4_enable_quotas(struct super_block *sb);

static const struct dquot_operations ext4_quota_operations = {
    .get_reserved_space = ext4_get_reserved_space,
    .write_dquot    = ext4_write_dquot,
    .acquire_dquot  = ext4_acquire_dquot,
    .release_dquot  = ext4_release_dquot,
    .mark_dirty = ext4_mark_dquot_dirty,
    .write_info = ext4_write_info,
    .alloc_dquot    = dquot_alloc,
    .destroy_dquot  = dquot_destroy,
};

static const struct quotactl_ops ext4_qctl_operations = {
    .quota_on   = ext4_quota_on,
    .quota_off  = ext4_quota_off,
    .quota_sync = dquot_quota_sync,
    .get_info   = dquot_get_dqinfo,
    .set_info   = dquot_set_dqinfo,
    .get_dqblk  = dquot_get_dqblk,
    .set_dqblk  = dquot_set_dqblk
};

static const struct quotactl_ops ext4_qctl_sysfile_operations = {
    .quota_on_meta  = ext4_quota_on_sysfile,
    .quota_off  = ext4_quota_off_sysfile,
    .quota_sync = dquot_quota_sync,
    .get_info   = dquot_get_dqinfo,
    .set_info   = dquot_set_dqinfo,
    .get_dqblk  = dquot_get_dqblk,
    .set_dqblk  = dquot_set_dqblk
};
#endif

static const struct super_operations ext4_sops = {
    .alloc_inode    = ext4_alloc_inode,
    .destroy_inode  = ext4_destroy_inode,
    .write_inode    = ext4_write_inode,
    .dirty_inode    = ext4_dirty_inode,
    .drop_inode = ext4_drop_inode,
    .evict_inode    = ext4_evict_inode,
    .put_super  = ext4_put_super,
    .sync_fs    = ext4_sync_fs,
    .freeze_fs  = ext4_freeze,
    .unfreeze_fs    = ext4_unfreeze,
    .statfs     = ext4_statfs,
    .remount_fs = ext4_remount,
    .show_options   = ext4_show_options,
#ifdef CONFIG_QUOTA
    .quota_read = ext4_quota_read,
    .quota_write    = ext4_quota_write,
#endif
    .bdev_try_to_free_page = bdev_try_to_free_page,
};

static const struct super_operations ext4_nojournal_sops = {
    .alloc_inode    = ext4_alloc_inode,
    .destroy_inode  = ext4_destroy_inode,
    .write_inode    = ext4_write_inode,
    .dirty_inode    = ext4_dirty_inode,
    .drop_inode = ext4_drop_inode,
    .evict_inode    = ext4_evict_inode,
    .put_super  = ext4_put_super,
    .statfs     = ext4_statfs,
    .remount_fs = ext4_remount,
    .show_options   = ext4_show_options,
#ifdef CONFIG_QUOTA
    .quota_read = ext4_quota_read,
    .quota_write    = ext4_quota_write,
#endif
    .bdev_try_to_free_page = bdev_try_to_free_page,
};

static const struct export_operations ext4_export_ops = {
    .fh_to_dentry = ext4_fh_to_dentry,
    .fh_to_parent = ext4_fh_to_parent,
    .get_parent = ext4_get_parent,
};

enum {
    Opt_bsd_df, Opt_minix_df, Opt_grpid, Opt_nogrpid,
    Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic, Opt_err_ro,
    Opt_nouid32, Opt_debug, Opt_removed,
    Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,
    Opt_auto_da_alloc, Opt_noauto_da_alloc, Opt_noload,
    Opt_commit, Opt_min_batch_time, Opt_max_batch_time,
    Opt_journal_dev, Opt_journal_checksum, Opt_journal_async_commit,
    Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
    Opt_data_err_abort, Opt_data_err_ignore,
    Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
    Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
    Opt_noquota, Opt_barrier, Opt_nobarrier, Opt_err,
    Opt_usrquota, Opt_grpquota, Opt_i_version,
    Opt_stripe, Opt_delalloc, Opt_nodelalloc, Opt_mblk_io_submit,
    Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity,
    Opt_inode_readahead_blks, Opt_journal_ioprio,
    Opt_dioread_nolock, Opt_dioread_lock,
    Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
    Opt_max_dir_size_kb,
};

static const match_table_t tokens = {
    {Opt_bsd_df, "bsddf"},
    {Opt_minix_df, "minixdf"},
    {Opt_grpid, "grpid"},
    {Opt_grpid, "bsdgroups"},
    {Opt_nogrpid, "nogrpid"},
    {Opt_nogrpid, "sysvgroups"},
    {Opt_resgid, "resgid=%u"},
    {Opt_resuid, "resuid=%u"},
    {Opt_sb, "sb=%u"},
    {Opt_err_cont, "errors=continue"},
    {Opt_err_panic, "errors=panic"},
    {Opt_err_ro, "errors=remount-ro"},
    {Opt_nouid32, "nouid32"},
    {Opt_debug, "debug"},
    {Opt_removed, "oldalloc"},
    {Opt_removed, "orlov"},
    {Opt_user_xattr, "user_xattr"},
    {Opt_nouser_xattr, "nouser_xattr"},
    {Opt_acl, "acl"},
    {Opt_noacl, "noacl"},
    {Opt_noload, "norecovery"},
    {Opt_noload, "noload"},
    {Opt_removed, "nobh"},
    {Opt_removed, "bh"},
    {Opt_commit, "commit=%u"},
    {Opt_min_batch_time, "min_batch_time=%u"},
    {Opt_max_batch_time, "max_batch_time=%u"},
    {Opt_journal_dev, "journal_dev=%u"},
    {Opt_journal_checksum, "journal_checksum"},
    {Opt_journal_async_commit, "journal_async_commit"},
    {Opt_abort, "abort"},
    {Opt_data_journal, "data=journal"},
    {Opt_data_ordered, "data=ordered"},
    {Opt_data_writeback, "data=writeback"},
    {Opt_data_err_abort, "data_err=abort"},
    {Opt_data_err_ignore, "data_err=ignore"},
    {Opt_offusrjquota, "usrjquota="},
    {Opt_usrjquota, "usrjquota=%s"},
    {Opt_offgrpjquota, "grpjquota="},
    {Opt_grpjquota, "grpjquota=%s"},
    {Opt_jqfmt_vfsold, "jqfmt=vfsold"},
    {Opt_jqfmt_vfsv0, "jqfmt=vfsv0"},
    {Opt_jqfmt_vfsv1, "jqfmt=vfsv1"},
    {Opt_grpquota, "grpquota"},
    {Opt_noquota, "noquota"},
    {Opt_quota, "quota"},
    {Opt_usrquota, "usrquota"},
    {Opt_barrier, "barrier=%u"},
    {Opt_barrier, "barrier"},
    {Opt_nobarrier, "nobarrier"},
    {Opt_i_version, "i_version"},
    {Opt_stripe, "stripe=%u"},
    {Opt_delalloc, "delalloc"},
    {Opt_nodelalloc, "nodelalloc"},
    {Opt_mblk_io_submit, "mblk_io_submit"},
    {Opt_nomblk_io_submit, "nomblk_io_submit"},
    {Opt_block_validity, "block_validity"},
    {Opt_noblock_validity, "noblock_validity"},
    {Opt_inode_readahead_blks, "inode_readahead_blks=%u"},
    {Opt_journal_ioprio, "journal_ioprio=%u"},
    {Opt_auto_da_alloc, "auto_da_alloc=%u"},
    {Opt_auto_da_alloc, "auto_da_alloc"},
    {Opt_noauto_da_alloc, "noauto_da_alloc"},
    {Opt_dioread_nolock, "dioread_nolock"},
    {Opt_dioread_lock, "dioread_lock"},
    {Opt_discard, "discard"},
    {Opt_nodiscard, "nodiscard"},
    {Opt_init_itable, "init_itable=%u"},
    {Opt_init_itable, "init_itable"},
    {Opt_noinit_itable, "noinit_itable"},
    {Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
    {Opt_removed, "check=none"},    /* mount option from ext2/3 */
    {Opt_removed, "nocheck"},   /* mount option from ext2/3 */
    {Opt_removed, "reservation"},   /* mount option from ext2/3 */
    {Opt_removed, "noreservation"}, /* mount option from ext2/3 */
    {Opt_removed, "journal=%u"},    /* mount option from ext2/3 */
    {Opt_err, NULL},
};

static ext4_fsblk_t get_sb_block(void **data)
{
    ext4_fsblk_t    sb_block;
    char        *options = (char *) *data;

    if (!options || strncmp(options, "sb=", 3) != 0)
        return 1;   /* Default location */

    options += 3;
    /* TODO: use simple_strtoll with >32bit ext4 */
    sb_block = simple_strtoul(options, &options, 0);
    if (*options && *options != ',') {
        printk(KERN_ERR "EXT4-fs: Invalid sb specification: %s\n",
               (char *) *data);
        return 1;
    }
    if (*options == ',')
        options++;
    *data = (void *) options;

    return sb_block;
}

#define DEFAULT_JOURNAL_IOPRIO (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 3))
static char deprecated_msg[] = "Mount option \"%s\" will be removed by %s\n"
    "Contact [email protected] if you think we should keep it.\n";

#ifdef CONFIG_QUOTA
static int set_qf_name(struct super_block *sb, int qtype, substring_t *args)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    char *qname;

    if (sb_any_quota_loaded(sb) &&
        !sbi->s_qf_names[qtype]) {
        ext4_msg(sb, KERN_ERR,
            "Cannot change journaled "
            "quota options when quota turned on");
        return -1;
    }
    qname = match_strdup(args);
    if (!qname) {
        ext4_msg(sb, KERN_ERR,
            "Not enough memory for storing quotafile name");
        return -1;
    }
    if (sbi->s_qf_names[qtype] &&
        strcmp(sbi->s_qf_names[qtype], qname)) {
        ext4_msg(sb, KERN_ERR,
            "%s quota file already specified", QTYPE2NAME(qtype));
        kfree(qname);
        return -1;
    }
    sbi->s_qf_names[qtype] = qname;
    if (strchr(sbi->s_qf_names[qtype], '/')) {
        ext4_msg(sb, KERN_ERR,
            "quotafile must be on filesystem root");
        kfree(sbi->s_qf_names[qtype]);
        sbi->s_qf_names[qtype] = NULL;
        return -1;
    }
    set_opt(sb, QUOTA);
    return 1;
}

static int clear_qf_name(struct super_block *sb, int qtype)
{

    struct ext4_sb_info *sbi = EXT4_SB(sb);

    if (sb_any_quota_loaded(sb) &&
        sbi->s_qf_names[qtype]) {
        ext4_msg(sb, KERN_ERR, "Cannot change journaled quota options"
            " when quota turned on");
        return -1;
    }
    /*
     * The space will be released later when all options are confirmed
     * to be correct
     */
    sbi->s_qf_names[qtype] = NULL;
    return 1;
}
#endif

#define MOPT_SET    0x0001
#define MOPT_CLEAR  0x0002
#define MOPT_NOSUPPORT  0x0004
#define MOPT_EXPLICIT   0x0008
#define MOPT_CLEAR_ERR  0x0010
#define MOPT_GTE0   0x0020
#ifdef CONFIG_QUOTA
#define MOPT_Q      0
#define MOPT_QFMT   0x0040
#else
#define MOPT_Q      MOPT_NOSUPPORT
#define MOPT_QFMT   MOPT_NOSUPPORT
#endif
#define MOPT_DATAJ  0x0080

static const struct mount_opts {
    int token;
    int mount_opt;
    int flags;
} ext4_mount_opts[] = {
    {Opt_minix_df, EXT4_MOUNT_MINIX_DF, MOPT_SET},
    {Opt_bsd_df, EXT4_MOUNT_MINIX_DF, MOPT_CLEAR},
    {Opt_grpid, EXT4_MOUNT_GRPID, MOPT_SET},
    {Opt_nogrpid, EXT4_MOUNT_GRPID, MOPT_CLEAR},
    {Opt_mblk_io_submit, EXT4_MOUNT_MBLK_IO_SUBMIT, MOPT_SET},
    {Opt_nomblk_io_submit, EXT4_MOUNT_MBLK_IO_SUBMIT, MOPT_CLEAR},
    {Opt_block_validity, EXT4_MOUNT_BLOCK_VALIDITY, MOPT_SET},
    {Opt_noblock_validity, EXT4_MOUNT_BLOCK_VALIDITY, MOPT_CLEAR},
    {Opt_dioread_nolock, EXT4_MOUNT_DIOREAD_NOLOCK, MOPT_SET},
    {Opt_dioread_lock, EXT4_MOUNT_DIOREAD_NOLOCK, MOPT_CLEAR},
    {Opt_discard, EXT4_MOUNT_DISCARD, MOPT_SET},
    {Opt_nodiscard, EXT4_MOUNT_DISCARD, MOPT_CLEAR},
    {Opt_delalloc, EXT4_MOUNT_DELALLOC, MOPT_SET | MOPT_EXPLICIT},
    {Opt_nodelalloc, EXT4_MOUNT_DELALLOC, MOPT_CLEAR | MOPT_EXPLICIT},
    {Opt_journal_checksum, EXT4_MOUNT_JOURNAL_CHECKSUM, MOPT_SET},
    {Opt_journal_async_commit, (EXT4_MOUNT_JOURNAL_ASYNC_COMMIT |
                    EXT4_MOUNT_JOURNAL_CHECKSUM), MOPT_SET},
    {Opt_noload, EXT4_MOUNT_NOLOAD, MOPT_SET},
    {Opt_err_panic, EXT4_MOUNT_ERRORS_PANIC, MOPT_SET | MOPT_CLEAR_ERR},
    {Opt_err_ro, EXT4_MOUNT_ERRORS_RO, MOPT_SET | MOPT_CLEAR_ERR},
    {Opt_err_cont, EXT4_MOUNT_ERRORS_CONT, MOPT_SET | MOPT_CLEAR_ERR},
    {Opt_data_err_abort, EXT4_MOUNT_DATA_ERR_ABORT, MOPT_SET},
    {Opt_data_err_ignore, EXT4_MOUNT_DATA_ERR_ABORT, MOPT_CLEAR},
    {Opt_barrier, EXT4_MOUNT_BARRIER, MOPT_SET},
    {Opt_nobarrier, EXT4_MOUNT_BARRIER, MOPT_CLEAR},
    {Opt_noauto_da_alloc, EXT4_MOUNT_NO_AUTO_DA_ALLOC, MOPT_SET},
    {Opt_auto_da_alloc, EXT4_MOUNT_NO_AUTO_DA_ALLOC, MOPT_CLEAR},
    {Opt_noinit_itable, EXT4_MOUNT_INIT_INODE_TABLE, MOPT_CLEAR},
    {Opt_commit, 0, MOPT_GTE0},
    {Opt_max_batch_time, 0, MOPT_GTE0},
    {Opt_min_batch_time, 0, MOPT_GTE0},
    {Opt_inode_readahead_blks, 0, MOPT_GTE0},
    {Opt_init_itable, 0, MOPT_GTE0},
    {Opt_stripe, 0, MOPT_GTE0},
    {Opt_data_journal, EXT4_MOUNT_JOURNAL_DATA, MOPT_DATAJ},
    {Opt_data_ordered, EXT4_MOUNT_ORDERED_DATA, MOPT_DATAJ},
    {Opt_data_writeback, EXT4_MOUNT_WRITEBACK_DATA, MOPT_DATAJ},
#ifdef CONFIG_EXT4_FS_XATTR
    {Opt_user_xattr, EXT4_MOUNT_XATTR_USER, MOPT_SET},
    {Opt_nouser_xattr, EXT4_MOUNT_XATTR_USER, MOPT_CLEAR},
#else
    {Opt_user_xattr, 0, MOPT_NOSUPPORT},
    {Opt_nouser_xattr, 0, MOPT_NOSUPPORT},
#endif
#ifdef CONFIG_EXT4_FS_POSIX_ACL
    {Opt_acl, EXT4_MOUNT_POSIX_ACL, MOPT_SET},
    {Opt_noacl, EXT4_MOUNT_POSIX_ACL, MOPT_CLEAR},
#else
    {Opt_acl, 0, MOPT_NOSUPPORT},
    {Opt_noacl, 0, MOPT_NOSUPPORT},
#endif
    {Opt_nouid32, EXT4_MOUNT_NO_UID32, MOPT_SET},
    {Opt_debug, EXT4_MOUNT_DEBUG, MOPT_SET},
    {Opt_quota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA, MOPT_SET | MOPT_Q},
    {Opt_usrquota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA,
                            MOPT_SET | MOPT_Q},
    {Opt_grpquota, EXT4_MOUNT_QUOTA | EXT4_MOUNT_GRPQUOTA,
                            MOPT_SET | MOPT_Q},
    {Opt_noquota, (EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA |
               EXT4_MOUNT_GRPQUOTA), MOPT_CLEAR | MOPT_Q},
    {Opt_usrjquota, 0, MOPT_Q},
    {Opt_grpjquota, 0, MOPT_Q},
    {Opt_offusrjquota, 0, MOPT_Q},
    {Opt_offgrpjquota, 0, MOPT_Q},
    {Opt_jqfmt_vfsold, QFMT_VFS_OLD, MOPT_QFMT},
    {Opt_jqfmt_vfsv0, QFMT_VFS_V0, MOPT_QFMT},
    {Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
    {Opt_max_dir_size_kb, 0, MOPT_GTE0},
    {Opt_err, 0, 0}
};

static int handle_mount_opt(struct super_block *sb, char *opt, int token,
                substring_t *args, unsigned long *journal_devnum,
                unsigned int *journal_ioprio, int is_remount)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    const struct mount_opts *m;
    kuid_t uid;
    kgid_t gid;
    int arg = 0;

#ifdef CONFIG_QUOTA
    if (token == Opt_usrjquota)
        return set_qf_name(sb, USRQUOTA, &args[0]);
    else if (token == Opt_grpjquota)
        return set_qf_name(sb, GRPQUOTA, &args[0]);
    else if (token == Opt_offusrjquota)
        return clear_qf_name(sb, USRQUOTA);
    else if (token == Opt_offgrpjquota)
        return clear_qf_name(sb, GRPQUOTA);
#endif
    if (args->from && match_int(args, &arg))
        return -1;
    switch (token) {
    case Opt_noacl:
    case Opt_nouser_xattr:
        ext4_msg(sb, KERN_WARNING, deprecated_msg, opt, "3.5");
        break;
    case Opt_sb:
        return 1;   /* handled by get_sb_block() */
    case Opt_removed:
        ext4_msg(sb, KERN_WARNING,
             "Ignoring removed %s option", opt);
        return 1;
    case Opt_resuid:
        uid = make_kuid(current_user_ns(), arg);
        if (!uid_valid(uid)) {
            ext4_msg(sb, KERN_ERR, "Invalid uid value %d", arg);
            return -1;
        }
        sbi->s_resuid = uid;
        return 1;
    case Opt_resgid:
        gid = make_kgid(current_user_ns(), arg);
        if (!gid_valid(gid)) {
            ext4_msg(sb, KERN_ERR, "Invalid gid value %d", arg);
            return -1;
        }
        sbi->s_resgid = gid;
        return 1;
    case Opt_abort:
        sbi->s_mount_flags |= EXT4_MF_FS_ABORTED;
        return 1;
    case Opt_i_version:
        sb->s_flags |= MS_I_VERSION;
        return 1;
    case Opt_journal_dev:
        if (is_remount) {
            ext4_msg(sb, KERN_ERR,
                 "Cannot specify journal on remount");
            return -1;
        }
        *journal_devnum = arg;
        return 1;
    case Opt_journal_ioprio:
        if (arg < 0 || arg > 7)
            return -1;
        *journal_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, arg);
        return 1;
    }

    for (m = ext4_mount_opts; m->token != Opt_err; m++) {
        if (token != m->token)
            continue;
        if (args->from && (m->flags & MOPT_GTE0) && (arg < 0))
            return -1;
        if (m->flags & MOPT_EXPLICIT)
            set_opt2(sb, EXPLICIT_DELALLOC);
        if (m->flags & MOPT_CLEAR_ERR)
            clear_opt(sb, ERRORS_MASK);
        if (token == Opt_noquota && sb_any_quota_loaded(sb)) {
            ext4_msg(sb, KERN_ERR, "Cannot change quota "
                 "options when quota turned on");
            return -1;
        }

        if (m->flags & MOPT_NOSUPPORT) {
            ext4_msg(sb, KERN_ERR, "%s option not supported", opt);
        } else if (token == Opt_commit) {
            if (arg == 0)
                arg = JBD2_DEFAULT_MAX_COMMIT_AGE;
            sbi->s_commit_interval = HZ * arg;
        } else if (token == Opt_max_batch_time) {
            if (arg == 0)
                arg = EXT4_DEF_MAX_BATCH_TIME;
            sbi->s_max_batch_time = arg;
        } else if (token == Opt_min_batch_time) {
            sbi->s_min_batch_time = arg;
        } else if (token == Opt_inode_readahead_blks) {
            if (arg > (1 << 30))
                return -1;
            if (arg && !is_power_of_2(arg)) {
                ext4_msg(sb, KERN_ERR,
                     "EXT4-fs: inode_readahead_blks"
                     " must be a power of 2");
                return -1;
            }
            sbi->s_inode_readahead_blks = arg;
        } else if (token == Opt_init_itable) {
            set_opt(sb, INIT_INODE_TABLE);
            if (!args->from)
                arg = EXT4_DEF_LI_WAIT_MULT;
            sbi->s_li_wait_mult = arg;
        } else if (token == Opt_max_dir_size_kb) {
            sbi->s_max_dir_size_kb = arg;
        } else if (token == Opt_stripe) {
            sbi->s_stripe = arg;
        } else if (m->flags & MOPT_DATAJ) {
            if (is_remount) {
                if (!sbi->s_journal)
                    ext4_msg(sb, KERN_WARNING, "Remounting file system with no journal so ignoring journalled data option");
                else if (test_opt(sb, DATA_FLAGS) !=
                     m->mount_opt) {
                    ext4_msg(sb, KERN_ERR,
                     "Cannot change data mode on remount");
                    return -1;
                }
            } else {
                clear_opt(sb, DATA_FLAGS);
                sbi->s_mount_opt |= m->mount_opt;
            }
#ifdef CONFIG_QUOTA
        } else if (m->flags & MOPT_QFMT) {
            if (sb_any_quota_loaded(sb) &&
                sbi->s_jquota_fmt != m->mount_opt) {
                ext4_msg(sb, KERN_ERR, "Cannot "
                     "change journaled quota options "
                     "when quota turned on");
                return -1;
            }
            sbi->s_jquota_fmt = m->mount_opt;
#endif
        } else {
            if (!args->from)
                arg = 1;
            if (m->flags & MOPT_CLEAR)
                arg = !arg;
            else if (unlikely(!(m->flags & MOPT_SET))) {
                ext4_msg(sb, KERN_WARNING,
                     "buggy handling of option %s", opt);
                WARN_ON(1);
                return -1;
            }
            if (arg != 0)
                sbi->s_mount_opt |= m->mount_opt;
            else
                sbi->s_mount_opt &= ~m->mount_opt;
        }
        return 1;
    }
    ext4_msg(sb, KERN_ERR, "Unrecognized mount option \"%s\" "
         "or missing value", opt);
    return -1;
}

static int parse_options(char *options, struct super_block *sb,
             unsigned long *journal_devnum,
             unsigned int *journal_ioprio,
             int is_remount)
{
#ifdef CONFIG_QUOTA
    struct ext4_sb_info *sbi = EXT4_SB(sb);
#endif
    char *p;
    substring_t args[MAX_OPT_ARGS];
    int token;

    if (!options)
        return 1;

    while ((p = strsep(&options, ",")) != NULL) {
        if (!*p)
            continue;
        /*
         * Initialize args struct so we know whether arg was
         * found; some options take optional arguments.
         */
        args[0].to = args[0].from = NULL;
        token = match_token(p, tokens, args);
        if (handle_mount_opt(sb, p, token, args, journal_devnum,
                     journal_ioprio, is_remount) < 0)
            return 0;
    }
#ifdef CONFIG_QUOTA
    if (sbi->s_qf_names[USRQUOTA] || sbi->s_qf_names[GRPQUOTA]) {
        if (test_opt(sb, USRQUOTA) && sbi->s_qf_names[USRQUOTA])
            clear_opt(sb, USRQUOTA);

        if (test_opt(sb, GRPQUOTA) && sbi->s_qf_names[GRPQUOTA])
            clear_opt(sb, GRPQUOTA);

        if (test_opt(sb, GRPQUOTA) || test_opt(sb, USRQUOTA)) {
            ext4_msg(sb, KERN_ERR, "old and new quota "
                    "format mixing");
            return 0;
        }

        if (!sbi->s_jquota_fmt) {
            ext4_msg(sb, KERN_ERR, "journaled quota format "
                    "not specified");
            return 0;
        }
    } else {
        if (sbi->s_jquota_fmt) {
            ext4_msg(sb, KERN_ERR, "journaled quota format "
                    "specified with no journaling "
                    "enabled");
            return 0;
        }
    }
#endif
    return 1;
}

static inline void ext4_show_quota_options(struct seq_file *seq,
                       struct super_block *sb)
{
#if defined(CONFIG_QUOTA)
    struct ext4_sb_info *sbi = EXT4_SB(sb);

    if (sbi->s_jquota_fmt) {
        char *fmtname = "";

        switch (sbi->s_jquota_fmt) {
        case QFMT_VFS_OLD:
            fmtname = "vfsold";
            break;
        case QFMT_VFS_V0:
            fmtname = "vfsv0";
            break;
        case QFMT_VFS_V1:
            fmtname = "vfsv1";
            break;
        }
        seq_printf(seq, ",jqfmt=%s", fmtname);
    }

    if (sbi->s_qf_names[USRQUOTA])
        seq_printf(seq, ",usrjquota=%s", sbi->s_qf_names[USRQUOTA]);

    if (sbi->s_qf_names[GRPQUOTA])
        seq_printf(seq, ",grpjquota=%s", sbi->s_qf_names[GRPQUOTA]);

    if (test_opt(sb, USRQUOTA))
        seq_puts(seq, ",usrquota");

    if (test_opt(sb, GRPQUOTA))
        seq_puts(seq, ",grpquota");
#endif
}

static const char *token2str(int token)
{
    const struct match_token *t;

    for (t = tokens; t->token != Opt_err; t++)
        if (t->token == token && !strchr(t->pattern, '='))
            break;
    return t->pattern;
}

/*
 * Show an option if
 *  - it's set to a non-default value OR
 *  - if the per-sb default is different from the global default
 */
static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
                  int nodefs)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_super_block *es = sbi->s_es;
    int def_errors, def_mount_opt = nodefs ? 0 : sbi->s_def_mount_opt;
    const struct mount_opts *m;
    char sep = nodefs ? '\n' : ',';

#define SEQ_OPTS_PUTS(str) seq_printf(seq, "%c" str, sep)
#define SEQ_OPTS_PRINT(str, arg) seq_printf(seq, "%c" str, sep, arg)

    if (sbi->s_sb_block != 1)
        SEQ_OPTS_PRINT("sb=%llu", sbi->s_sb_block);

    for (m = ext4_mount_opts; m->token != Opt_err; m++) {
        int want_set = m->flags & MOPT_SET;
        if (((m->flags & (MOPT_SET|MOPT_CLEAR)) == 0) ||
            (m->flags & MOPT_CLEAR_ERR))
            continue;
        if (!(m->mount_opt & (sbi->s_mount_opt ^ def_mount_opt)))
            continue; /* skip if same as the default */
        if ((want_set &&
             (sbi->s_mount_opt & m->mount_opt) != m->mount_opt) ||
            (!want_set && (sbi->s_mount_opt & m->mount_opt)))
            continue; /* select Opt_noFoo vs Opt_Foo */
        SEQ_OPTS_PRINT("%s", token2str(m->token));
    }

    if (nodefs || !uid_eq(sbi->s_resuid, make_kuid(&init_user_ns, EXT4_DEF_RESUID)) ||
        le16_to_cpu(es->s_def_resuid) != EXT4_DEF_RESUID)
        SEQ_OPTS_PRINT("resuid=%u",
                from_kuid_munged(&init_user_ns, sbi->s_resuid));
    if (nodefs || !gid_eq(sbi->s_resgid, make_kgid(&init_user_ns, EXT4_DEF_RESGID)) ||
        le16_to_cpu(es->s_def_resgid) != EXT4_DEF_RESGID)
        SEQ_OPTS_PRINT("resgid=%u",
                from_kgid_munged(&init_user_ns, sbi->s_resgid));
    def_errors = nodefs ? -1 : le16_to_cpu(es->s_errors);
    if (test_opt(sb, ERRORS_RO) && def_errors != EXT4_ERRORS_RO)
        SEQ_OPTS_PUTS("errors=remount-ro");
    if (test_opt(sb, ERRORS_CONT) && def_errors != EXT4_ERRORS_CONTINUE)
        SEQ_OPTS_PUTS("errors=continue");
    if (test_opt(sb, ERRORS_PANIC) && def_errors != EXT4_ERRORS_PANIC)
        SEQ_OPTS_PUTS("errors=panic");
    if (nodefs || sbi->s_commit_interval != JBD2_DEFAULT_MAX_COMMIT_AGE*HZ)
        SEQ_OPTS_PRINT("commit=%lu", sbi->s_commit_interval / HZ);
    if (nodefs || sbi->s_min_batch_time != EXT4_DEF_MIN_BATCH_TIME)
        SEQ_OPTS_PRINT("min_batch_time=%u", sbi->s_min_batch_time);
    if (nodefs || sbi->s_max_batch_time != EXT4_DEF_MAX_BATCH_TIME)
        SEQ_OPTS_PRINT("max_batch_time=%u", sbi->s_max_batch_time);
    if (sb->s_flags & MS_I_VERSION)
        SEQ_OPTS_PUTS("i_version");
    if (nodefs || sbi->s_stripe)
        SEQ_OPTS_PRINT("stripe=%lu", sbi->s_stripe);
    if (EXT4_MOUNT_DATA_FLAGS & (sbi->s_mount_opt ^ def_mount_opt)) {
        if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
            SEQ_OPTS_PUTS("data=journal");
        else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA)
            SEQ_OPTS_PUTS("data=ordered");
        else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA)
            SEQ_OPTS_PUTS("data=writeback");
    }
    if (nodefs ||
        sbi->s_inode_readahead_blks != EXT4_DEF_INODE_READAHEAD_BLKS)
        SEQ_OPTS_PRINT("inode_readahead_blks=%u",
                   sbi->s_inode_readahead_blks);

    if (nodefs || (test_opt(sb, INIT_INODE_TABLE) &&
               (sbi->s_li_wait_mult != EXT4_DEF_LI_WAIT_MULT)))
        SEQ_OPTS_PRINT("init_itable=%u", sbi->s_li_wait_mult);
    if (nodefs || sbi->s_max_dir_size_kb)
        SEQ_OPTS_PRINT("max_dir_size_kb=%u", sbi->s_max_dir_size_kb);

    ext4_show_quota_options(seq, sb);
    return 0;
}

static int ext4_show_options(struct seq_file *seq, struct dentry *root)
{
    return _ext4_show_options(seq, root->d_sb, 0);
}

static int options_seq_show(struct seq_file *seq, void *offset)
{
    struct super_block *sb = seq->private;
    int rc;

    seq_puts(seq, (sb->s_flags & MS_RDONLY) ? "ro" : "rw");
    rc = _ext4_show_options(seq, sb, 1);
    seq_puts(seq, "\n");
    return rc;
}

static int options_open_fs(struct inode *inode, struct file *file)
{
    return single_open(file, options_seq_show, PDE(inode)->data);
}

static const struct file_operations ext4_seq_options_fops = {
    .owner = THIS_MODULE,
    .open = options_open_fs,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = single_release,
};

static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
                int read_only)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    int res = 0;

    if (le32_to_cpu(es->s_rev_level) > EXT4_MAX_SUPP_REV) {
        ext4_msg(sb, KERN_ERR, "revision level too high, "
             "forcing read-only mode");
        res = MS_RDONLY;
    }
    if (read_only)
        goto done;
    if (!(sbi->s_mount_state & EXT4_VALID_FS))
        ext4_msg(sb, KERN_WARNING, "warning: mounting unchecked fs, "
             "running e2fsck is recommended");
    else if ((sbi->s_mount_state & EXT4_ERROR_FS))
        ext4_msg(sb, KERN_WARNING,
             "warning: mounting fs with errors, "
             "running e2fsck is recommended");
    else if ((__s16) le16_to_cpu(es->s_max_mnt_count) > 0 &&
         le16_to_cpu(es->s_mnt_count) >=
         (unsigned short) (__s16) le16_to_cpu(es->s_max_mnt_count))
        ext4_msg(sb, KERN_WARNING,
             "warning: maximal mount count reached, "
             "running e2fsck is recommended");
    else if (le32_to_cpu(es->s_checkinterval) &&
        (le32_to_cpu(es->s_lastcheck) +
            le32_to_cpu(es->s_checkinterval) <= get_seconds()))
        ext4_msg(sb, KERN_WARNING,
             "warning: checktime reached, "
             "running e2fsck is recommended");
    if (!sbi->s_journal)
        es->s_state &= cpu_to_le16(~EXT4_VALID_FS);
    if (!(__s16) le16_to_cpu(es->s_max_mnt_count))
        es->s_max_mnt_count = cpu_to_le16(EXT4_DFL_MAX_MNT_COUNT);
    le16_add_cpu(&es->s_mnt_count, 1);
    es->s_mtime = cpu_to_le32(get_seconds());
    ext4_update_dynamic_rev(sb);
    if (sbi->s_journal)
        EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);

    ext4_commit_super(sb, 1);
done:
    if (test_opt(sb, DEBUG))
        printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
                "bpg=%lu, ipg=%lu, mo=%04x, mo2=%04x]\n",
            sb->s_blocksize,
            sbi->s_groups_count,
            EXT4_BLOCKS_PER_GROUP(sb),
            EXT4_INODES_PER_GROUP(sb),
            sbi->s_mount_opt, sbi->s_mount_opt2);

    cleancache_init_fs(sb);
    return res;
}

int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct flex_groups *new_groups;
    int size;

    if (!sbi->s_log_groups_per_flex)
        return 0;

    size = ext4_flex_group(sbi, ngroup - 1) + 1;
    if (size <= sbi->s_flex_groups_allocated)
        return 0;

    size = roundup_pow_of_two(size * sizeof(struct flex_groups));
    new_groups = ext4_kvzalloc(size, GFP_KERNEL);
    if (!new_groups) {
        ext4_msg(sb, KERN_ERR, "not enough memory for %d flex groups",
             size / (int) sizeof(struct flex_groups));
        return -ENOMEM;
    }

    if (sbi->s_flex_groups) {
        memcpy(new_groups, sbi->s_flex_groups,
               (sbi->s_flex_groups_allocated *
            sizeof(struct flex_groups)));
        ext4_kvfree(sbi->s_flex_groups);
    }
    sbi->s_flex_groups = new_groups;
    sbi->s_flex_groups_allocated = size / sizeof(struct flex_groups);
    return 0;
}

static int ext4_fill_flex_info(struct super_block *sb)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_group_desc *gdp = NULL;
    ext4_group_t flex_group;
    unsigned int groups_per_flex = 0;
    int i, err;

    sbi->s_log_groups_per_flex = sbi->s_es->s_log_groups_per_flex;
    if (sbi->s_log_groups_per_flex < 1 || sbi->s_log_groups_per_flex > 31) {
        sbi->s_log_groups_per_flex = 0;
        return 1;
    }
    groups_per_flex = 1U << sbi->s_log_groups_per_flex;

    err = ext4_alloc_flex_bg_array(sb, sbi->s_groups_count);
    if (err)
        goto failed;

    for (i = 0; i < sbi->s_groups_count; i++) {
        gdp = ext4_get_group_desc(sb, i, NULL);

        flex_group = ext4_flex_group(sbi, i);
        atomic_add(ext4_free_inodes_count(sb, gdp),
               &sbi->s_flex_groups[flex_group].free_inodes);
        atomic_add(ext4_free_group_clusters(sb, gdp),
               &sbi->s_flex_groups[flex_group].free_clusters);
        atomic_add(ext4_used_dirs_count(sb, gdp),
               &sbi->s_flex_groups[flex_group].used_dirs);
    }

    return 1;
failed:
    return 0;
}

static __le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
                   struct ext4_group_desc *gdp)
{
    int offset;
    __u16 crc = 0;
    __le32 le_group = cpu_to_le32(block_group);

    if ((sbi->s_es->s_feature_ro_compat &
         cpu_to_le32(EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))) {
        /* Use new metadata_csum algorithm */
        __u16 old_csum;
        __u32 csum32;

        old_csum = gdp->bg_checksum;
        gdp->bg_checksum = 0;
        csum32 = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&le_group,
                     sizeof(le_group));
        csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp,
                     sbi->s_desc_size);
        gdp->bg_checksum = old_csum;

        crc = csum32 & 0xFFFF;
        goto out;
    }

    /* old crc16 code */
    offset = offsetof(struct ext4_group_desc, bg_checksum);

    crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
    crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
    crc = crc16(crc, (__u8 *)gdp, offset);
    offset += sizeof(gdp->bg_checksum); /* skip checksum */
    /* for checksum of struct ext4_group_desc do the rest...*/
    if ((sbi->s_es->s_feature_incompat &
         cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
        offset < le16_to_cpu(sbi->s_es->s_desc_size))
        crc = crc16(crc, (__u8 *)gdp + offset,
                le16_to_cpu(sbi->s_es->s_desc_size) -
                offset);

out:
    return cpu_to_le16(crc);
}

int ext4_group_desc_csum_verify(struct super_block *sb, __u32 block_group,
                struct ext4_group_desc *gdp)
{
    if (ext4_has_group_desc_csum(sb) &&
        (gdp->bg_checksum != ext4_group_desc_csum(EXT4_SB(sb),
                              block_group, gdp)))
        return 0;

    return 1;
}

void ext4_group_desc_csum_set(struct super_block *sb, __u32 block_group,
                  struct ext4_group_desc *gdp)
{
    if (!ext4_has_group_desc_csum(sb))
        return;
    gdp->bg_checksum = ext4_group_desc_csum(EXT4_SB(sb), block_group, gdp);
}

/* Called at mount-time, super-block is locked */
static int ext4_check_descriptors(struct super_block *sb,
                  ext4_group_t *first_not_zeroed)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    ext4_fsblk_t first_block = le32_to_cpu(sbi->s_es->s_first_data_block);
    ext4_fsblk_t last_block;
    ext4_fsblk_t block_bitmap;
    ext4_fsblk_t inode_bitmap;
    ext4_fsblk_t inode_table;
    int flexbg_flag = 0;
    ext4_group_t i, grp = sbi->s_groups_count;

    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
        flexbg_flag = 1;

    ext4_debug("Checking group descriptors");

    for (i = 0; i < sbi->s_groups_count; i++) {
        struct ext4_group_desc *gdp = ext4_get_group_desc(sb, i, NULL);

        if (i == sbi->s_groups_count - 1 || flexbg_flag)
            last_block = ext4_blocks_count(sbi->s_es) - 1;
        else
            last_block = first_block +
                (EXT4_BLOCKS_PER_GROUP(sb) - 1);

        if ((grp == sbi->s_groups_count) &&
           !(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED)))
            grp = i;

        block_bitmap = ext4_block_bitmap(sb, gdp);
        if (block_bitmap < first_block || block_bitmap > last_block) {
            ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                   "Block bitmap for group %u not in group "
                   "(block %llu)!", i, block_bitmap);
            return 0;
        }
        inode_bitmap = ext4_inode_bitmap(sb, gdp);
        if (inode_bitmap < first_block || inode_bitmap > last_block) {
            ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                   "Inode bitmap for group %u not in group "
                   "(block %llu)!", i, inode_bitmap);
            return 0;
        }
        inode_table = ext4_inode_table(sb, gdp);
        if (inode_table < first_block ||
            inode_table + sbi->s_itb_per_group - 1 > last_block) {
            ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                   "Inode table for group %u not in group "
                   "(block %llu)!", i, inode_table);
            return 0;
        }
        ext4_lock_group(sb, i);
        if (!ext4_group_desc_csum_verify(sb, i, gdp)) {
            ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                 "Checksum for group %u failed (%u!=%u)",
                 i, le16_to_cpu(ext4_group_desc_csum(sbi, i,
                     gdp)), le16_to_cpu(gdp->bg_checksum));
            if (!(sb->s_flags & MS_RDONLY)) {
                ext4_unlock_group(sb, i);
                return 0;
            }
        }
        ext4_unlock_group(sb, i);
        if (!flexbg_flag)
            first_block += EXT4_BLOCKS_PER_GROUP(sb);
    }
    if (NULL != first_not_zeroed)
        *first_not_zeroed = grp;

    ext4_free_blocks_count_set(sbi->s_es,
                   EXT4_C2B(sbi, ext4_count_free_clusters(sb)));
    sbi->s_es->s_free_inodes_count =cpu_to_le32(ext4_count_free_inodes(sb));
    return 1;
}

/* ext4_orphan_cleanup() walks a singly-linked list of inodes (starting at
 * the superblock) which were deleted from all directories, but held open by
 * a process at the time of a crash.  We walk the list and try to delete these
 * inodes at recovery time (only with a read-write filesystem).
 *
 * In order to keep the orphan inode chain consistent during traversal (in
 * case of crash during recovery), we link each inode into the superblock
 * orphan list_head and handle it the same way as an inode deletion during
 * normal operation (which journals the operations for us).
 *
 * We only do an iget() and an iput() on each inode, which is very safe if we
 * accidentally point at an in-use or already deleted inode.  The worst that
 * can happen in this case is that we get a "bit already cleared" message from
 * ext4_free_inode().  The only reason we would point at a wrong inode is if
 * e2fsck was run on this filesystem, and it must have already done the orphan
 * inode cleanup for us, so we can safely abort without any further action.
 */
static void ext4_orphan_cleanup(struct super_block *sb,
                struct ext4_super_block *es)
{
    unsigned int s_flags = sb->s_flags;
    int nr_orphans = 0, nr_truncates = 0;
#ifdef CONFIG_QUOTA
    int i;
#endif
    if (!es->s_last_orphan) {
        jbd_debug(4, "no orphan inodes to clean up\n");
        return;
    }

    if (bdev_read_only(sb->s_bdev)) {
        ext4_msg(sb, KERN_ERR, "write access "
            "unavailable, skipping orphan cleanup");
        return;
    }

    /* Check if feature set would not allow a r/w mount */
    if (!ext4_feature_set_ok(sb, 0)) {
        ext4_msg(sb, KERN_INFO, "Skipping orphan cleanup due to "
             "unknown ROCOMPAT features");
        return;
    }

    if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
        /* don't clear list on RO mount w/ errors */
        if (es->s_last_orphan && !(s_flags & MS_RDONLY)) {
            jbd_debug(1, "Errors on filesystem, "
                  "clearing orphan list.\n");
            es->s_last_orphan = 0;
        }
        jbd_debug(1, "Skipping orphan recovery on fs with errors.\n");
        return;
    }

    if (s_flags & MS_RDONLY) {
        ext4_msg(sb, KERN_INFO, "orphan cleanup on readonly fs");
        sb->s_flags &= ~MS_RDONLY;
    }
#ifdef CONFIG_QUOTA
    /* Needed for iput() to work correctly and not trash data */
    sb->s_flags |= MS_ACTIVE;
    /* Turn on quotas so that they are updated correctly */
    for (i = 0; i < MAXQUOTAS; i++) {
        if (EXT4_SB(sb)->s_qf_names[i]) {
            int ret = ext4_quota_on_mount(sb, i);
            if (ret < 0)
                ext4_msg(sb, KERN_ERR,
                    "Cannot turn on journaled "
                    "quota: error %d", ret);
        }
    }
#endif

    while (es->s_last_orphan) {
        struct inode *inode;

        inode = ext4_orphan_get(sb, le32_to_cpu(es->s_last_orphan));
        if (IS_ERR(inode)) {
            es->s_last_orphan = 0;
            break;
        }

        list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);
        dquot_initialize(inode);
        if (inode->i_nlink) {
            ext4_msg(sb, KERN_DEBUG,
                "%s: truncating inode %lu to %lld bytes",
                __func__, inode->i_ino, inode->i_size);
            jbd_debug(2, "truncating inode %lu to %lld bytes\n",
                  inode->i_ino, inode->i_size);
            ext4_truncate(inode);
            nr_truncates++;
        } else {
            ext4_msg(sb, KERN_DEBUG,
                "%s: deleting unreferenced inode %lu",
                __func__, inode->i_ino);
            jbd_debug(2, "deleting unreferenced inode %lu\n",
                  inode->i_ino);
            nr_orphans++;
        }
        iput(inode);  /* The delete magic happens here! */
    }

#define PLURAL(x) (x), ((x) == 1) ? "" : "s"

    if (nr_orphans)
        ext4_msg(sb, KERN_INFO, "%d orphan inode%s deleted",
               PLURAL(nr_orphans));
    if (nr_truncates)
        ext4_msg(sb, KERN_INFO, "%d truncate%s cleaned up",
               PLURAL(nr_truncates));
#ifdef CONFIG_QUOTA
    /* Turn quotas off */
    for (i = 0; i < MAXQUOTAS; i++) {
        if (sb_dqopt(sb)->files[i])
            dquot_quota_off(sb, i);
    }
#endif
    sb->s_flags = s_flags; /* Restore MS_RDONLY status */
}

/*
 * Maximal extent format file size.
 * Resulting logical blkno at s_maxbytes must fit in our on-disk
 * extent format containers, within a sector_t, and within i_blocks
 * in the vfs.  ext4 inode has 48 bits of i_block in fsblock units,
 * so that won't be a limiting factor.
 *
 * However there is other limiting factor. We do store extents in the form
 * of starting block and length, hence the resulting length of the extent
 * covering maximum file size must fit into on-disk format containers as
 * well. Given that length is always by 1 unit bigger than max unit (because
 * we count 0 as well) we have to lower the s_maxbytes by one fs block.
 *
 * Note, this does *not* consider any metadata overhead for vfs i_blocks.
 */
static loff_t ext4_max_size(int blkbits, int has_huge_files)
{
    loff_t res;
    loff_t upper_limit = MAX_LFS_FILESIZE;

    /* small i_blocks in vfs inode? */
    if (!has_huge_files || sizeof(blkcnt_t) < sizeof(u64)) {
        /*
         * CONFIG_LBDAF is not enabled implies the inode
         * i_block represent total blocks in 512 bytes
         * 32 == size of vfs inode i_blocks * 8
         */
        upper_limit = (1LL << 32) - 1;

        /* total blocks in file system block size */
        upper_limit >>= (blkbits - 9);
        upper_limit <<= blkbits;
    }

    /*
     * 32-bit extent-start container, ee_block. We lower the maxbytes
     * by one fs block, so ee_len can cover the extent of maximum file
     * size
     */
    res = (1LL << 32) - 1;
    res <<= blkbits;

    /* Sanity check against vm- & vfs- imposed limits */
    if (res > upper_limit)
        res = upper_limit;

    return res;
}

/*
 * Maximal bitmap file size.  There is a direct, and {,double-,triple-}indirect
 * block limit, and also a limit of (2^48 - 1) 512-byte sectors in i_blocks.
 * We need to be 1 filesystem block less than the 2^48 sector limit.
 */
static loff_t ext4_max_bitmap_size(int bits, int has_huge_files)
{
    loff_t res = EXT4_NDIR_BLOCKS;
    int meta_blocks;
    loff_t upper_limit;
    /* This is calculated to be the largest file size for a dense, block
     * mapped file such that the file's total number of 512-byte sectors,
     * including data and all indirect blocks, does not exceed (2^48 - 1).
     *
     * __u32 i_blocks_lo and _u16 i_blocks_high represent the total
     * number of 512-byte sectors of the file.
     */

    if (!has_huge_files || sizeof(blkcnt_t) < sizeof(u64)) {
        /*
         * !has_huge_files or CONFIG_LBDAF not enabled implies that
         * the inode i_block field represents total file blocks in
         * 2^32 512-byte sectors == size of vfs inode i_blocks * 8
         */
        upper_limit = (1LL << 32) - 1;

        /* total blocks in file system block size */
        upper_limit >>= (bits - 9);

    } else {
        /*
         * We use 48 bit ext4_inode i_blocks
         * With EXT4_HUGE_FILE_FL set the i_blocks
         * represent total number of blocks in
         * file system block size
         */
        upper_limit = (1LL << 48) - 1;

    }

    /* indirect blocks */
    meta_blocks = 1;
    /* double indirect blocks */
    meta_blocks += 1 + (1LL << (bits-2));
    /* tripple indirect blocks */
    meta_blocks += 1 + (1LL << (bits-2)) + (1LL << (2*(bits-2)));

    upper_limit -= meta_blocks;
    upper_limit <<= bits;

    res += 1LL << (bits-2);
    res += 1LL << (2*(bits-2));
    res += 1LL << (3*(bits-2));
    res <<= bits;
    if (res > upper_limit)
        res = upper_limit;

    if (res > MAX_LFS_FILESIZE)
        res = MAX_LFS_FILESIZE;

    return res;
}

static ext4_fsblk_t descriptor_loc(struct super_block *sb,
                   ext4_fsblk_t logical_sb_block, int nr)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    ext4_group_t bg, first_meta_bg;
    int has_super = 0;

    first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);

    if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
        nr < first_meta_bg)
        return logical_sb_block + nr + 1;
    bg = sbi->s_desc_per_block * nr;
    if (ext4_bg_has_super(sb, bg))
        has_super = 1;

    return (has_super + ext4_group_first_block_no(sb, bg));
}

static unsigned long ext4_get_stripe_size(struct ext4_sb_info *sbi)
{
    unsigned long stride = le16_to_cpu(sbi->s_es->s_raid_stride);
    unsigned long stripe_width =
            le32_to_cpu(sbi->s_es->s_raid_stripe_width);
    int ret;

    if (sbi->s_stripe && sbi->s_stripe <= sbi->s_blocks_per_group)
        ret = sbi->s_stripe;
    else if (stripe_width <= sbi->s_blocks_per_group)
        ret = stripe_width;
    else if (stride <= sbi->s_blocks_per_group)
        ret = stride;
    else
        ret = 0;

    /*
     * If the stripe width is 1, this makes no sense and
     * we set it to 0 to turn off stripe handling code.
     */
    if (ret <= 1)
        ret = 0;

    return ret;
}

/* sysfs supprt */

struct ext4_attr {
    struct attribute attr;
    ssize_t (*show)(struct ext4_attr *, struct ext4_sb_info *, char *);
    ssize_t (*store)(struct ext4_attr *, struct ext4_sb_info *,
             const char *, size_t);
    int offset;
};

static int parse_strtoul(const char *buf,
        unsigned long max, unsigned long *value)
{
    char *endp;

    *value = simple_strtoul(skip_spaces(buf), &endp, 0);
    endp = skip_spaces(endp);
    if (*endp || *value > max)
        return -EINVAL;

    return 0;
}

static ssize_t delayed_allocation_blocks_show(struct ext4_attr *a,
                          struct ext4_sb_info *sbi,
                          char *buf)
{
    return snprintf(buf, PAGE_SIZE, "%llu\n",
        (s64) EXT4_C2B(sbi,
            percpu_counter_sum(&sbi->s_dirtyclusters_counter)));
}

static ssize_t session_write_kbytes_show(struct ext4_attr *a,
                     struct ext4_sb_info *sbi, char *buf)
{
    struct super_block *sb = sbi->s_buddy_cache->i_sb;

    if (!sb->s_bdev->bd_part)
        return snprintf(buf, PAGE_SIZE, "0\n");
    return snprintf(buf, PAGE_SIZE, "%lu\n",
            (part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
             sbi->s_sectors_written_start) >> 1);
}

static ssize_t lifetime_write_kbytes_show(struct ext4_attr *a,
                      struct ext4_sb_info *sbi, char *buf)
{
    struct super_block *sb = sbi->s_buddy_cache->i_sb;

    if (!sb->s_bdev->bd_part)
        return snprintf(buf, PAGE_SIZE, "0\n");
    return snprintf(buf, PAGE_SIZE, "%llu\n",
            (unsigned long long)(sbi->s_kbytes_written +
            ((part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
              EXT4_SB(sb)->s_sectors_written_start) >> 1)));
}

static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
                      struct ext4_sb_info *sbi,
                      const char *buf, size_t count)
{
    unsigned long t;

    if (parse_strtoul(buf, 0x40000000, &t))
        return -EINVAL;

    if (t && !is_power_of_2(t))
        return -EINVAL;

    sbi->s_inode_readahead_blks = t;
    return count;
}

static ssize_t sbi_ui_show(struct ext4_attr *a,
               struct ext4_sb_info *sbi, char *buf)
{
    unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);

    return snprintf(buf, PAGE_SIZE, "%u\n", *ui);
}

static ssize_t sbi_ui_store(struct ext4_attr *a,
                struct ext4_sb_info *sbi,
                const char *buf, size_t count)
{
    unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);
    unsigned long t;

    if (parse_strtoul(buf, 0xffffffff, &t))
        return -EINVAL;
    *ui = t;
    return count;
}

static ssize_t trigger_test_error(struct ext4_attr *a,
                  struct ext4_sb_info *sbi,
                  const char *buf, size_t count)
{
    int len = count;

    if (!capable(CAP_SYS_ADMIN))
        return -EPERM;

    if (len && buf[len-1] == '\n')
        len--;

    if (len)
        ext4_error(sbi->s_sb, "%.*s", len, buf);
    return count;
}

#define EXT4_ATTR_OFFSET(_name,_mode,_show,_store,_elname) \
static struct ext4_attr ext4_attr_##_name = {           \
    .attr = {.name = __stringify(_name), .mode = _mode },   \
    .show   = _show,                    \
    .store  = _store,                   \
    .offset = offsetof(struct ext4_sb_info, _elname),   \
}
#define EXT4_ATTR(name, mode, show, store) \
static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)

#define EXT4_INFO_ATTR(name) EXT4_ATTR(name, 0444, NULL, NULL)
#define EXT4_RO_ATTR(name) EXT4_ATTR(name, 0444, name##_show, NULL)
#define EXT4_RW_ATTR(name) EXT4_ATTR(name, 0644, name##_show, name##_store)
#define EXT4_RW_ATTR_SBI_UI(name, elname)   \
    EXT4_ATTR_OFFSET(name, 0644, sbi_ui_show, sbi_ui_store, elname)
#define ATTR_LIST(name) &ext4_attr_##name.attr

EXT4_RO_ATTR(delayed_allocation_blocks);
EXT4_RO_ATTR(session_write_kbytes);
EXT4_RO_ATTR(lifetime_write_kbytes);
EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
         inode_readahead_blks_store, s_inode_readahead_blks);
EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats);
EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan);
EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan);
EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);
EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc);
EXT4_RW_ATTR_SBI_UI(max_writeback_mb_bump, s_max_writeback_mb_bump);
EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb);
EXT4_ATTR(trigger_fs_error, 0200, NULL, trigger_test_error);

static struct attribute *ext4_attrs[] = {
    ATTR_LIST(delayed_allocation_blocks),
    ATTR_LIST(session_write_kbytes),
    ATTR_LIST(lifetime_write_kbytes),
    ATTR_LIST(inode_readahead_blks),
    ATTR_LIST(inode_goal),
    ATTR_LIST(mb_stats),
    ATTR_LIST(mb_max_to_scan),
    ATTR_LIST(mb_min_to_scan),
    ATTR_LIST(mb_order2_req),
    ATTR_LIST(mb_stream_req),
    ATTR_LIST(mb_group_prealloc),
    ATTR_LIST(max_writeback_mb_bump),
    ATTR_LIST(extent_max_zeroout_kb),
    ATTR_LIST(trigger_fs_error),
    NULL,
};

/* Features this copy of ext4 supports */
EXT4_INFO_ATTR(lazy_itable_init);
EXT4_INFO_ATTR(batched_discard);
EXT4_INFO_ATTR(meta_bg_resize);

static struct attribute *ext4_feat_attrs[] = {
    ATTR_LIST(lazy_itable_init),
    ATTR_LIST(batched_discard),
    ATTR_LIST(meta_bg_resize),
    NULL,
};

static ssize_t ext4_attr_show(struct kobject *kobj,
                  struct attribute *attr, char *buf)
{
    struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
                        s_kobj);
    struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);

    return a->show ? a->show(a, sbi, buf) : 0;
}

static ssize_t ext4_attr_store(struct kobject *kobj,
                   struct attribute *attr,
                   const char *buf, size_t len)
{
    struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
                        s_kobj);
    struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);

    return a->store ? a->store(a, sbi, buf, len) : 0;
}

static void ext4_sb_release(struct kobject *kobj)
{
    struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
                        s_kobj);
    complete(&sbi->s_kobj_unregister);
}

static const struct sysfs_ops ext4_attr_ops = {
    .show   = ext4_attr_show,
    .store  = ext4_attr_store,
};

static struct kobj_type ext4_ktype = {
    .default_attrs  = ext4_attrs,
    .sysfs_ops  = &ext4_attr_ops,
    .release    = ext4_sb_release,
};

static void ext4_feat_release(struct kobject *kobj)
{
    complete(&ext4_feat->f_kobj_unregister);
}

static struct kobj_type ext4_feat_ktype = {
    .default_attrs  = ext4_feat_attrs,
    .sysfs_ops  = &ext4_attr_ops,
    .release    = ext4_feat_release,
};

/*
 * Check whether this filesystem can be mounted based on
 * the features present and the RDONLY/RDWR mount requested.
 * Returns 1 if this filesystem can be mounted as requested,
 * 0 if it cannot be.
 */
static int ext4_feature_set_ok(struct super_block *sb, int readonly)
{
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, ~EXT4_FEATURE_INCOMPAT_SUPP)) {
        ext4_msg(sb, KERN_ERR,
            "Couldn't mount because of "
            "unsupported optional features (%x)",
            (le32_to_cpu(EXT4_SB(sb)->s_es->s_feature_incompat) &
            ~EXT4_FEATURE_INCOMPAT_SUPP));
        return 0;
    }

    if (readonly)
        return 1;

    /* Check that feature set is OK for a read-write mount */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT4_FEATURE_RO_COMPAT_SUPP)) {
        ext4_msg(sb, KERN_ERR, "couldn't mount RDWR because of "
             "unsupported optional features (%x)",
             (le32_to_cpu(EXT4_SB(sb)->s_es->s_feature_ro_compat) &
                ~EXT4_FEATURE_RO_COMPAT_SUPP));
        return 0;
    }
    /*
     * Large file size enabled file system can only be mounted
     * read-write on 32-bit systems if kernel is built with CONFIG_LBDAF
     */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_HUGE_FILE)) {
        if (sizeof(blkcnt_t) < sizeof(u64)) {
            ext4_msg(sb, KERN_ERR, "Filesystem with huge files "
                 "cannot be mounted RDWR without "
                 "CONFIG_LBDAF");
            return 0;
        }
    }
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_BIGALLOC) &&
        !EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS)) {
        ext4_msg(sb, KERN_ERR,
             "Can't support bigalloc feature without "
             "extents feature\n");
        return 0;
    }

#ifndef CONFIG_QUOTA
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA) &&
        !readonly) {
        ext4_msg(sb, KERN_ERR,
             "Filesystem with quota feature cannot be mounted RDWR "
             "without CONFIG_QUOTA");
        return 0;
    }
#endif  /* CONFIG_QUOTA */
    return 1;
}

/*
 * This function is called once a day if we have errors logged
 * on the file system
 */
static void print_daily_error_info(unsigned long arg)
{
    struct super_block *sb = (struct super_block *) arg;
    struct ext4_sb_info *sbi;
    struct ext4_super_block *es;

    sbi = EXT4_SB(sb);
    es = sbi->s_es;

    if (es->s_error_count)
        ext4_msg(sb, KERN_NOTICE, "error count: %u",
             le32_to_cpu(es->s_error_count));
    if (es->s_first_error_time) {
        printk(KERN_NOTICE "EXT4-fs (%s): initial error at %u: %.*s:%d",
               sb->s_id, le32_to_cpu(es->s_first_error_time),
               (int) sizeof(es->s_first_error_func),
               es->s_first_error_func,
               le32_to_cpu(es->s_first_error_line));
        if (es->s_first_error_ino)
            printk(": inode %u",
                   le32_to_cpu(es->s_first_error_ino));
        if (es->s_first_error_block)
            printk(": block %llu", (unsigned long long)
                   le64_to_cpu(es->s_first_error_block));
        printk("\n");
    }
    if (es->s_last_error_time) {
        printk(KERN_NOTICE "EXT4-fs (%s): last error at %u: %.*s:%d",
               sb->s_id, le32_to_cpu(es->s_last_error_time),
               (int) sizeof(es->s_last_error_func),
               es->s_last_error_func,
               le32_to_cpu(es->s_last_error_line));
        if (es->s_last_error_ino)
            printk(": inode %u",
                   le32_to_cpu(es->s_last_error_ino));
        if (es->s_last_error_block)
            printk(": block %llu", (unsigned long long)
                   le64_to_cpu(es->s_last_error_block));
        printk("\n");
    }
    mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);  /* Once a day */
}

/* Find next suitable group and run ext4_init_inode_table */
static int ext4_run_li_request(struct ext4_li_request *elr)
{
    struct ext4_group_desc *gdp = NULL;
    ext4_group_t group, ngroups;
    struct super_block *sb;
    unsigned long timeout = 0;
    int ret = 0;

    sb = elr->lr_super;
    ngroups = EXT4_SB(sb)->s_groups_count;

    sb_start_write(sb);
    for (group = elr->lr_next_group; group < ngroups; group++) {
        gdp = ext4_get_group_desc(sb, group, NULL);
        if (!gdp) {
            ret = 1;
            break;
        }

        if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED)))
            break;
    }

    if (group == ngroups)
        ret = 1;

    if (!ret) {
        timeout = jiffies;
        ret = ext4_init_inode_table(sb, group,
                        elr->lr_timeout ? 0 : 1);
        if (elr->lr_timeout == 0) {
            timeout = (jiffies - timeout) *
                  elr->lr_sbi->s_li_wait_mult;
            elr->lr_timeout = timeout;
        }
        elr->lr_next_sched = jiffies + elr->lr_timeout;
        elr->lr_next_group = group + 1;
    }
    sb_end_write(sb);

    return ret;
}

/*
 * Remove lr_request from the list_request and free the
 * request structure. Should be called with li_list_mtx held
 */
static void ext4_remove_li_request(struct ext4_li_request *elr)
{
    struct ext4_sb_info *sbi;

    if (!elr)
        return;

    sbi = elr->lr_sbi;

    list_del(&elr->lr_request);
    sbi->s_li_request = NULL;
    kfree(elr);
}

static void ext4_unregister_li_request(struct super_block *sb)
{
    mutex_lock(&ext4_li_mtx);
    if (!ext4_li_info) {
        mutex_unlock(&ext4_li_mtx);
        return;
    }

    mutex_lock(&ext4_li_info->li_list_mtx);
    ext4_remove_li_request(EXT4_SB(sb)->s_li_request);
    mutex_unlock(&ext4_li_info->li_list_mtx);
    mutex_unlock(&ext4_li_mtx);
}

static struct task_struct *ext4_lazyinit_task;

/*
 * This is the function where ext4lazyinit thread lives. It walks
 * through the request list searching for next scheduled filesystem.
 * When such a fs is found, run the lazy initialization request
 * (ext4_rn_li_request) and keep track of the time spend in this
 * function. Based on that time we compute next schedule time of
 * the request. When walking through the list is complete, compute
 * next waking time and put itself into sleep.
 */
static int ext4_lazyinit_thread(void *arg)
{
    struct ext4_lazy_init *eli = (struct ext4_lazy_init *)arg;
    struct list_head *pos, *n;
    struct ext4_li_request *elr;
    unsigned long next_wakeup, cur;

    BUG_ON(NULL == eli);

cont_thread:
    while (true) {
        next_wakeup = MAX_JIFFY_OFFSET;

        mutex_lock(&eli->li_list_mtx);
        if (list_empty(&eli->li_request_list)) {
            mutex_unlock(&eli->li_list_mtx);
            goto exit_thread;
        }

        list_for_each_safe(pos, n, &eli->li_request_list) {
            elr = list_entry(pos, struct ext4_li_request,
                     lr_request);

            if (time_after_eq(jiffies, elr->lr_next_sched)) {
                if (ext4_run_li_request(elr) != 0) {
                    /* error, remove the lazy_init job */
                    ext4_remove_li_request(elr);
                    continue;
                }
            }

            if (time_before(elr->lr_next_sched, next_wakeup))
                next_wakeup = elr->lr_next_sched;
        }
        mutex_unlock(&eli->li_list_mtx);

        try_to_freeze();

        cur = jiffies;
        if ((time_after_eq(cur, next_wakeup)) ||
            (MAX_JIFFY_OFFSET == next_wakeup)) {
            cond_resched();
            continue;
        }

        schedule_timeout_interruptible(next_wakeup - cur);

        if (kthread_should_stop()) {
            ext4_clear_request_list();
            goto exit_thread;
        }
    }

exit_thread:
    /*
     * It looks like the request list is empty, but we need
     * to check it under the li_list_mtx lock, to prevent any
     * additions into it, and of course we should lock ext4_li_mtx
     * to atomically free the list and ext4_li_info, because at
     * this point another ext4 filesystem could be registering
     * new one.
     */
    mutex_lock(&ext4_li_mtx);
    mutex_lock(&eli->li_list_mtx);
    if (!list_empty(&eli->li_request_list)) {
        mutex_unlock(&eli->li_list_mtx);
        mutex_unlock(&ext4_li_mtx);
        goto cont_thread;
    }
    mutex_unlock(&eli->li_list_mtx);
    kfree(ext4_li_info);
    ext4_li_info = NULL;
    mutex_unlock(&ext4_li_mtx);

    return 0;
}

static void ext4_clear_request_list(void)
{
    struct list_head *pos, *n;
    struct ext4_li_request *elr;

    mutex_lock(&ext4_li_info->li_list_mtx);
    list_for_each_safe(pos, n, &ext4_li_info->li_request_list) {
        elr = list_entry(pos, struct ext4_li_request,
                 lr_request);
        ext4_remove_li_request(elr);
    }
    mutex_unlock(&ext4_li_info->li_list_mtx);
}

static int ext4_run_lazyinit_thread(void)
{
    ext4_lazyinit_task = kthread_run(ext4_lazyinit_thread,
                     ext4_li_info, "ext4lazyinit");
    if (IS_ERR(ext4_lazyinit_task)) {
        int err = PTR_ERR(ext4_lazyinit_task);
        ext4_clear_request_list();
        kfree(ext4_li_info);
        ext4_li_info = NULL;
        printk(KERN_CRIT "EXT4-fs: error %d creating inode table "
                 "initialization thread\n",
                 err);
        return err;
    }
    ext4_li_info->li_state |= EXT4_LAZYINIT_RUNNING;
    return 0;
}

/*
 * Check whether it make sense to run itable init. thread or not.
 * If there is at least one uninitialized inode table, return
 * corresponding group number, else the loop goes through all
 * groups and return total number of groups.
 */
static ext4_group_t ext4_has_uninit_itable(struct super_block *sb)
{
    ext4_group_t group, ngroups = EXT4_SB(sb)->s_groups_count;
    struct ext4_group_desc *gdp = NULL;

    for (group = 0; group < ngroups; group++) {
        gdp = ext4_get_group_desc(sb, group, NULL);
        if (!gdp)
            continue;

        if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED)))
            break;
    }

    return group;
}

static int ext4_li_info_new(void)
{
    struct ext4_lazy_init *eli = NULL;

    eli = kzalloc(sizeof(*eli), GFP_KERNEL);
    if (!eli)
        return -ENOMEM;

    INIT_LIST_HEAD(&eli->li_request_list);
    mutex_init(&eli->li_list_mtx);

    eli->li_state |= EXT4_LAZYINIT_QUIT;

    ext4_li_info = eli;

    return 0;
}

static struct ext4_li_request *ext4_li_request_new(struct super_block *sb,
                        ext4_group_t start)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_li_request *elr;
    unsigned long rnd;

    elr = kzalloc(sizeof(*elr), GFP_KERNEL);
    if (!elr)
        return NULL;

    elr->lr_super = sb;
    elr->lr_sbi = sbi;
    elr->lr_next_group = start;

    /*
     * Randomize first schedule time of the request to
     * spread the inode table initialization requests
     * better.
     */
    get_random_bytes(&rnd, sizeof(rnd));
    elr->lr_next_sched = jiffies + (unsigned long)rnd %
                 (EXT4_DEF_LI_MAX_START_DELAY * HZ);

    return elr;
}

static int ext4_register_li_request(struct super_block *sb,
                    ext4_group_t first_not_zeroed)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_li_request *elr;
    ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
    int ret = 0;

    if (sbi->s_li_request != NULL) {
        /*
         * Reset timeout so it can be computed again, because
         * s_li_wait_mult might have changed.
         */
        sbi->s_li_request->lr_timeout = 0;
        return 0;
    }

    if (first_not_zeroed == ngroups ||
        (sb->s_flags & MS_RDONLY) ||
        !test_opt(sb, INIT_INODE_TABLE))
        return 0;

    elr = ext4_li_request_new(sb, first_not_zeroed);
    if (!elr)
        return -ENOMEM;

    mutex_lock(&ext4_li_mtx);

    if (NULL == ext4_li_info) {
        ret = ext4_li_info_new();
        if (ret)
            goto out;
    }

    mutex_lock(&ext4_li_info->li_list_mtx);
    list_add(&elr->lr_request, &ext4_li_info->li_request_list);
    mutex_unlock(&ext4_li_info->li_list_mtx);

    sbi->s_li_request = elr;
    /*
     * set elr to NULL here since it has been inserted to
     * the request_list and the removal and free of it is
     * handled by ext4_clear_request_list from now on.
     */
    elr = NULL;

    if (!(ext4_li_info->li_state & EXT4_LAZYINIT_RUNNING)) {
        ret = ext4_run_lazyinit_thread();
        if (ret)
            goto out;
    }
out:
    mutex_unlock(&ext4_li_mtx);
    if (ret)
        kfree(elr);
    return ret;
}

/*
 * We do not need to lock anything since this is called on
 * module unload.
 */
static void ext4_destroy_lazyinit_thread(void)
{
    /*
     * If thread exited earlier
     * there's nothing to be done.
     */
    if (!ext4_li_info || !ext4_lazyinit_task)
        return;

    kthread_stop(ext4_lazyinit_task);
}

static int set_journal_csum_feature_set(struct super_block *sb)
{
    int ret = 1;
    int compat, incompat;
    struct ext4_sb_info *sbi = EXT4_SB(sb);

    if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
        /* journal checksum v2 */
        compat = 0;
        incompat = JBD2_FEATURE_INCOMPAT_CSUM_V2;
    } else {
        /* journal checksum v1 */
        compat = JBD2_FEATURE_COMPAT_CHECKSUM;
        incompat = 0;
    }

    if (test_opt(sb, JOURNAL_ASYNC_COMMIT)) {
        ret = jbd2_journal_set_features(sbi->s_journal,
                compat, 0,
                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT |
                incompat);
    } else if (test_opt(sb, JOURNAL_CHECKSUM)) {
        ret = jbd2_journal_set_features(sbi->s_journal,
                compat, 0,
                incompat);
        jbd2_journal_clear_features(sbi->s_journal, 0, 0,
                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
    } else {
        jbd2_journal_clear_features(sbi->s_journal,
                JBD2_FEATURE_COMPAT_CHECKSUM, 0,
                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT |
                JBD2_FEATURE_INCOMPAT_CSUM_V2);
    }

    return ret;
}

/*
 * Note: calculating the overhead so we can be compatible with
 * historical BSD practice is quite difficult in the face of
 * clusters/bigalloc.  This is because multiple metadata blocks from
 * different block group can end up in the same allocation cluster.
 * Calculating the exact overhead in the face of clustered allocation
 * requires either O(all block bitmaps) in memory or O(number of block
 * groups**2) in time.  We will still calculate the superblock for
 * older file systems --- and if we come across with a bigalloc file
 * system with zero in s_overhead_clusters the estimate will be close to
 * correct especially for very large cluster sizes --- but for newer
 * file systems, it's better to calculate this figure once at mkfs
 * time, and store it in the superblock.  If the superblock value is
 * present (even for non-bigalloc file systems), we will use it.
 */
static int count_overhead(struct super_block *sb, ext4_group_t grp,
              char *buf)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_group_desc  *gdp;
    ext4_fsblk_t        first_block, last_block, b;
    ext4_group_t        i, ngroups = ext4_get_groups_count(sb);
    int         s, j, count = 0;

    if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_BIGALLOC))
        return (ext4_bg_has_super(sb, grp) + ext4_bg_num_gdb(sb, grp) +
            sbi->s_itb_per_group + 2);

    first_block = le32_to_cpu(sbi->s_es->s_first_data_block) +
        (grp * EXT4_BLOCKS_PER_GROUP(sb));
    last_block = first_block + EXT4_BLOCKS_PER_GROUP(sb) - 1;
    for (i = 0; i < ngroups; i++) {
        gdp = ext4_get_group_desc(sb, i, NULL);
        b = ext4_block_bitmap(sb, gdp);
        if (b >= first_block && b <= last_block) {
            ext4_set_bit(EXT4_B2C(sbi, b - first_block), buf);
            count++;
        }
        b = ext4_inode_bitmap(sb, gdp);
        if (b >= first_block && b <= last_block) {
            ext4_set_bit(EXT4_B2C(sbi, b - first_block), buf);
            count++;
        }
        b = ext4_inode_table(sb, gdp);
        if (b >= first_block && b + sbi->s_itb_per_group <= last_block)
            for (j = 0; j < sbi->s_itb_per_group; j++, b++) {
                int c = EXT4_B2C(sbi, b - first_block);
                ext4_set_bit(c, buf);
                count++;
            }
        if (i != grp)
            continue;
        s = 0;
        if (ext4_bg_has_super(sb, grp)) {
            ext4_set_bit(s++, buf);
            count++;
        }
        for (j = ext4_bg_num_gdb(sb, grp); j > 0; j--) {
            ext4_set_bit(EXT4_B2C(sbi, s++), buf);
            count++;
        }
    }
    if (!count)
        return 0;
    return EXT4_CLUSTERS_PER_GROUP(sb) -
        ext4_count_free(buf, EXT4_CLUSTERS_PER_GROUP(sb) / 8);
}

/*
 * Compute the overhead and stash it in sbi->s_overhead
 */
int ext4_calculate_overhead(struct super_block *sb)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_super_block *es = sbi->s_es;
    ext4_group_t i, ngroups = ext4_get_groups_count(sb);
    ext4_fsblk_t overhead = 0;
    char *buf = (char *) get_zeroed_page(GFP_KERNEL);

    memset(buf, 0, PAGE_SIZE);
    if (!buf)
        return -ENOMEM;

    /*
     * Compute the overhead (FS structures).  This is constant
     * for a given filesystem unless the number of block groups
     * changes so we cache the previous value until it does.
     */

    /*
     * All of the blocks before first_data_block are overhead
     */
    overhead = EXT4_B2C(sbi, le32_to_cpu(es->s_first_data_block));

    /*
     * Add the overhead found in each block group
     */
    for (i = 0; i < ngroups; i++) {
        int blks;

        blks = count_overhead(sb, i, buf);
        overhead += blks;
        if (blks)
            memset(buf, 0, PAGE_SIZE);
        cond_resched();
    }
    sbi->s_overhead = overhead;
    smp_wmb();
    free_page((unsigned long) buf);
    return 0;
}

static int ext4_fill_super(struct super_block *sb, void *data, int silent)
{
    char *orig_data = kstrdup(data, GFP_KERNEL);
    struct buffer_head *bh;
    struct ext4_super_block *es = NULL;
    struct ext4_sb_info *sbi;
    ext4_fsblk_t block;
    ext4_fsblk_t sb_block = get_sb_block(&data);
    ext4_fsblk_t logical_sb_block;
    unsigned long offset = 0;
    unsigned long journal_devnum = 0;
    unsigned long def_mount_opts;
    struct inode *root;
    char *cp;
    const char *descr;
    int ret = -ENOMEM;
    int blocksize, clustersize;
    unsigned int db_count;
    unsigned int i;
    int needs_recovery, has_huge_files, has_bigalloc;
    __u64 blocks_count;
    int err;
    unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
    ext4_group_t first_not_zeroed;

    sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
    if (!sbi)
        goto out_free_orig;

    sbi->s_blockgroup_lock =
        kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
    if (!sbi->s_blockgroup_lock) {
        kfree(sbi);
        goto out_free_orig;
    }
    sb->s_fs_info = sbi;
    sbi->s_sb = sb;
    sbi->s_mount_opt = 0;
    sbi->s_resuid = make_kuid(&init_user_ns, EXT4_DEF_RESUID);
    sbi->s_resgid = make_kgid(&init_user_ns, EXT4_DEF_RESGID);
    sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
    sbi->s_sb_block = sb_block;
    if (sb->s_bdev->bd_part)
        sbi->s_sectors_written_start =
            part_stat_read(sb->s_bdev->bd_part, sectors[1]);

    /* Cleanup superblock name */
    for (cp = sb->s_id; (cp = strchr(cp, '/'));)
        *cp = '!';

    ret = -EINVAL;
    blocksize = sb_min_blocksize(sb, EXT4_MIN_BLOCK_SIZE);
    if (!blocksize) {
        ext4_msg(sb, KERN_ERR, "unable to set blocksize");
        goto out_fail;
    }

    /*
     * The ext4 superblock will not be buffer aligned for other than 1kB
     * block sizes.  We need to calculate the offset from buffer start.
     */
    if (blocksize != EXT4_MIN_BLOCK_SIZE) {
        logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
        offset = do_div(logical_sb_block, blocksize);
    } else {
        logical_sb_block = sb_block;
    }

    if (!(bh = sb_bread(sb, logical_sb_block))) {
        ext4_msg(sb, KERN_ERR, "unable to read superblock");
        goto out_fail;
    }
    /*
     * Note: s_es must be initialized as soon as possible because
     *       some ext4 macro-instructions depend on its value
     */
    es = (struct ext4_super_block *) (bh->b_data + offset);
    sbi->s_es = es;
    sb->s_magic = le16_to_cpu(es->s_magic);
    if (sb->s_magic != EXT4_SUPER_MAGIC)
        goto cantfind_ext4;
    sbi->s_kbytes_written = le64_to_cpu(es->s_kbytes_written);

    /* Warn if metadata_csum and gdt_csum are both set. */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) &&
        EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
        ext4_warning(sb, KERN_INFO "metadata_csum and uninit_bg are "
                 "redundant flags; please run fsck.");

    /* Check for a known checksum algorithm */
    if (!ext4_verify_csum_type(sb, es)) {
        ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
             "unknown checksum algorithm.");
        silent = 1;
        goto cantfind_ext4;
    }

    /* Load the checksum driver */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
        sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
        if (IS_ERR(sbi->s_chksum_driver)) {
            ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
            ret = PTR_ERR(sbi->s_chksum_driver);
            sbi->s_chksum_driver = NULL;
            goto failed_mount;
        }
    }

    /* Check superblock checksum */
    if (!ext4_superblock_csum_verify(sb, es)) {
        ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
             "invalid superblock checksum.  Run e2fsck?");
        silent = 1;
        goto cantfind_ext4;
    }

    /* Precompute checksum seed for all metadata */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
            EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        sbi->s_csum_seed = ext4_chksum(sbi, ~0, es->s_uuid,
                           sizeof(es->s_uuid));

    /* Set defaults before we parse the mount options */
    def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
    set_opt(sb, INIT_INODE_TABLE);
    if (def_mount_opts & EXT4_DEFM_DEBUG)
        set_opt(sb, DEBUG);
    if (def_mount_opts & EXT4_DEFM_BSDGROUPS)
        set_opt(sb, GRPID);
    if (def_mount_opts & EXT4_DEFM_UID16)
        set_opt(sb, NO_UID32);
    /* xattr user namespace & acls are now defaulted on */
#ifdef CONFIG_EXT4_FS_XATTR
    set_opt(sb, XATTR_USER);
#endif
#ifdef CONFIG_EXT4_FS_POSIX_ACL
    set_opt(sb, POSIX_ACL);
#endif
    set_opt(sb, MBLK_IO_SUBMIT);
    if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_DATA)
        set_opt(sb, JOURNAL_DATA);
    else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_ORDERED)
        set_opt(sb, ORDERED_DATA);
    else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_WBACK)
        set_opt(sb, WRITEBACK_DATA);

    if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_PANIC)
        set_opt(sb, ERRORS_PANIC);
    else if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_CONTINUE)
        set_opt(sb, ERRORS_CONT);
    else
        set_opt(sb, ERRORS_RO);
    if (def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY)
        set_opt(sb, BLOCK_VALIDITY);
    if (def_mount_opts & EXT4_DEFM_DISCARD)
        set_opt(sb, DISCARD);

    sbi->s_resuid = make_kuid(&init_user_ns, le16_to_cpu(es->s_def_resuid));
    sbi->s_resgid = make_kgid(&init_user_ns, le16_to_cpu(es->s_def_resgid));
    sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
    sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
    sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;

    if ((def_mount_opts & EXT4_DEFM_NOBARRIER) == 0)
        set_opt(sb, BARRIER);

    /*
     * enable delayed allocation by default
     * Use -o nodelalloc to turn it off
     */
    if (!IS_EXT3_SB(sb) && !IS_EXT2_SB(sb) &&
        ((def_mount_opts & EXT4_DEFM_NODELALLOC) == 0))
        set_opt(sb, DELALLOC);

    /*
     * set default s_li_wait_mult for lazyinit, for the case there is
     * no mount option specified.
     */
    sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;

    if (!parse_options((char *) sbi->s_es->s_mount_opts, sb,
               &journal_devnum, &journal_ioprio, 0)) {
        ext4_msg(sb, KERN_WARNING,
             "failed to parse options in superblock: %s",
             sbi->s_es->s_mount_opts);
    }
    sbi->s_def_mount_opt = sbi->s_mount_opt;
    if (!parse_options((char *) data, sb, &journal_devnum,
               &journal_ioprio, 0))
        goto failed_mount;

    if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
        printk_once(KERN_WARNING "EXT4-fs: Warning: mounting "
                "with data=journal disables delayed "
                "allocation and O_DIRECT support!\n");
        if (test_opt2(sb, EXPLICIT_DELALLOC)) {
            ext4_msg(sb, KERN_ERR, "can't mount with "
                 "both data=journal and delalloc");
            goto failed_mount;
        }
        if (test_opt(sb, DIOREAD_NOLOCK)) {
            ext4_msg(sb, KERN_ERR, "can't mount with "
                 "both data=journal and delalloc");
            goto failed_mount;
        }
        if (test_opt(sb, DELALLOC))
            clear_opt(sb, DELALLOC);
    }

    blocksize = BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
    if (test_opt(sb, DIOREAD_NOLOCK)) {
        if (blocksize < PAGE_SIZE) {
            ext4_msg(sb, KERN_ERR, "can't mount with "
                 "dioread_nolock if block size != PAGE_SIZE");
            goto failed_mount;
        }
    }

    sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
        (test_opt(sb, POSIX_ACL) ? MS_POSIXACL : 0);

    if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV &&
        (EXT4_HAS_COMPAT_FEATURE(sb, ~0U) ||
         EXT4_HAS_RO_COMPAT_FEATURE(sb, ~0U) ||
         EXT4_HAS_INCOMPAT_FEATURE(sb, ~0U)))
        ext4_msg(sb, KERN_WARNING,
               "feature flags set on rev 0 fs, "
               "running e2fsck is recommended");

    if (IS_EXT2_SB(sb)) {
        if (ext2_feature_set_ok(sb))
            ext4_msg(sb, KERN_INFO, "mounting ext2 file system "
                 "using the ext4 subsystem");
        else {
            ext4_msg(sb, KERN_ERR, "couldn't mount as ext2 due "
                 "to feature incompatibilities");
            goto failed_mount;
        }
    }

    if (IS_EXT3_SB(sb)) {
        if (ext3_feature_set_ok(sb))
            ext4_msg(sb, KERN_INFO, "mounting ext3 file system "
                 "using the ext4 subsystem");
        else {
            ext4_msg(sb, KERN_ERR, "couldn't mount as ext3 due "
                 "to feature incompatibilities");
            goto failed_mount;
        }
    }

    /*
     * Check feature flags regardless of the revision level, since we
     * previously didn't change the revision level when setting the flags,
     * so there is a chance incompat flags are set on a rev 0 filesystem.
     */
    if (!ext4_feature_set_ok(sb, (sb->s_flags & MS_RDONLY)))
        goto failed_mount;

    if (blocksize < EXT4_MIN_BLOCK_SIZE ||
        blocksize > EXT4_MAX_BLOCK_SIZE) {
        ext4_msg(sb, KERN_ERR,
               "Unsupported filesystem blocksize %d", blocksize);
        goto failed_mount;
    }

    if (sb->s_blocksize != blocksize) {
        /* Validate the filesystem blocksize */
        if (!sb_set_blocksize(sb, blocksize)) {
            ext4_msg(sb, KERN_ERR, "bad block size %d",
                    blocksize);
            goto failed_mount;
        }

        brelse(bh);
        logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
        offset = do_div(logical_sb_block, blocksize);
        bh = sb_bread(sb, logical_sb_block);
        if (!bh) {
            ext4_msg(sb, KERN_ERR,
                   "Can't read superblock on 2nd try");
            goto failed_mount;
        }
        es = (struct ext4_super_block *)(bh->b_data + offset);
        sbi->s_es = es;
        if (es->s_magic != cpu_to_le16(EXT4_SUPER_MAGIC)) {
            ext4_msg(sb, KERN_ERR,
                   "Magic mismatch, very weird!");
            goto failed_mount;
        }
    }

    has_huge_files = EXT4_HAS_RO_COMPAT_FEATURE(sb,
                EXT4_FEATURE_RO_COMPAT_HUGE_FILE);
    sbi->s_bitmap_maxbytes = ext4_max_bitmap_size(sb->s_blocksize_bits,
                              has_huge_files);
    sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);

    if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
        sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
        sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
    } else {
        sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
        sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
        if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
            (!is_power_of_2(sbi->s_inode_size)) ||
            (sbi->s_inode_size > blocksize)) {
            ext4_msg(sb, KERN_ERR,
                   "unsupported inode size: %d",
                   sbi->s_inode_size);
            goto failed_mount;
        }
        if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE)
            sb->s_time_gran = 1 << (EXT4_EPOCH_BITS - 2);
    }

    sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_64BIT)) {
        if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE_64BIT ||
            sbi->s_desc_size > EXT4_MAX_DESC_SIZE ||
            !is_power_of_2(sbi->s_desc_size)) {
            ext4_msg(sb, KERN_ERR,
                   "unsupported descriptor size %lu",
                   sbi->s_desc_size);
            goto failed_mount;
        }
    } else
        sbi->s_desc_size = EXT4_MIN_DESC_SIZE;

    sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
    sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
    if (EXT4_INODE_SIZE(sb) == 0 || EXT4_INODES_PER_GROUP(sb) == 0)
        goto cantfind_ext4;

    sbi->s_inodes_per_block = blocksize / EXT4_INODE_SIZE(sb);
    if (sbi->s_inodes_per_block == 0)
        goto cantfind_ext4;
    sbi->s_itb_per_group = sbi->s_inodes_per_group /
                    sbi->s_inodes_per_block;
    sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
    sbi->s_sbh = bh;
    sbi->s_mount_state = le16_to_cpu(es->s_state);
    sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb));
    sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb));

    for (i = 0; i < 4; i++)
        sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
    sbi->s_def_hash_version = es->s_def_hash_version;
    i = le32_to_cpu(es->s_flags);
    if (i & EXT2_FLAGS_UNSIGNED_HASH)
        sbi->s_hash_unsigned = 3;
    else if ((i & EXT2_FLAGS_SIGNED_HASH) == 0) {
#ifdef __CHAR_UNSIGNED__
        es->s_flags |= cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);
        sbi->s_hash_unsigned = 3;
#else
        es->s_flags |= cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);
#endif
    }

    /* Handle clustersize */
    clustersize = BLOCK_SIZE << le32_to_cpu(es->s_log_cluster_size);
    has_bigalloc = EXT4_HAS_RO_COMPAT_FEATURE(sb,
                EXT4_FEATURE_RO_COMPAT_BIGALLOC);
    if (has_bigalloc) {
        if (clustersize < blocksize) {
            ext4_msg(sb, KERN_ERR,
                 "cluster size (%d) smaller than "
                 "block size (%d)", clustersize, blocksize);
            goto failed_mount;
        }
        sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
            le32_to_cpu(es->s_log_block_size);
        sbi->s_clusters_per_group =
            le32_to_cpu(es->s_clusters_per_group);
        if (sbi->s_clusters_per_group > blocksize * 8) {
            ext4_msg(sb, KERN_ERR,
                 "#clusters per group too big: %lu",
                 sbi->s_clusters_per_group);
            goto failed_mount;
        }
        if (sbi->s_blocks_per_group !=
            (sbi->s_clusters_per_group * (clustersize / blocksize))) {
            ext4_msg(sb, KERN_ERR, "blocks per group (%lu) and "
                 "clusters per group (%lu) inconsistent",
                 sbi->s_blocks_per_group,
                 sbi->s_clusters_per_group);
            goto failed_mount;
        }
    } else {
        if (clustersize != blocksize) {
            ext4_warning(sb, "fragment/cluster size (%d) != "
                     "block size (%d)", clustersize,
                     blocksize);
            clustersize = blocksize;
        }
        if (sbi->s_blocks_per_group > blocksize * 8) {
            ext4_msg(sb, KERN_ERR,
                 "#blocks per group too big: %lu",
                 sbi->s_blocks_per_group);
            goto failed_mount;
        }
        sbi->s_clusters_per_group = sbi->s_blocks_per_group;
        sbi->s_cluster_bits = 0;
    }
    sbi->s_cluster_ratio = clustersize / blocksize;

    if (sbi->s_inodes_per_group > blocksize * 8) {
        ext4_msg(sb, KERN_ERR,
               "#inodes per group too big: %lu",
               sbi->s_inodes_per_group);
        goto failed_mount;
    }

    /*
     * Test whether we have more sectors than will fit in sector_t,
     * and whether the max offset is addressable by the page cache.
     */
    err = generic_check_addressable(sb->s_blocksize_bits,
                    ext4_blocks_count(es));
    if (err) {
        ext4_msg(sb, KERN_ERR, "filesystem"
             " too large to mount safely on this system");
        if (sizeof(sector_t) < 8)
            ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
        ret = err;
        goto failed_mount;
    }

    if (EXT4_BLOCKS_PER_GROUP(sb) == 0)
        goto cantfind_ext4;

    /* check blocks count against device size */
    blocks_count = sb->s_bdev->bd_inode->i_size >> sb->s_blocksize_bits;
    if (blocks_count && ext4_blocks_count(es) > blocks_count) {
        ext4_msg(sb, KERN_WARNING, "bad geometry: block count %llu "
               "exceeds size of device (%llu blocks)",
               ext4_blocks_count(es), blocks_count);
        goto failed_mount;
    }

    /*
     * It makes no sense for the first data block to be beyond the end
     * of the filesystem.
     */
    if (le32_to_cpu(es->s_first_data_block) >= ext4_blocks_count(es)) {
        ext4_msg(sb, KERN_WARNING, "bad geometry: first data "
             "block %u is beyond end of filesystem (%llu)",
             le32_to_cpu(es->s_first_data_block),
             ext4_blocks_count(es));
        goto failed_mount;
    }
    blocks_count = (ext4_blocks_count(es) -
            le32_to_cpu(es->s_first_data_block) +
            EXT4_BLOCKS_PER_GROUP(sb) - 1);
    do_div(blocks_count, EXT4_BLOCKS_PER_GROUP(sb));
    if (blocks_count > ((uint64_t)1<<32) - EXT4_DESC_PER_BLOCK(sb)) {
        ext4_msg(sb, KERN_WARNING, "groups count too large: %u "
               "(block count %llu, first data block %u, "
               "blocks per group %lu)", sbi->s_groups_count,
               ext4_blocks_count(es),
               le32_to_cpu(es->s_first_data_block),
               EXT4_BLOCKS_PER_GROUP(sb));
        goto failed_mount;
    }
    sbi->s_groups_count = blocks_count;
    sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count,
            (EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb)));
    db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
           EXT4_DESC_PER_BLOCK(sb);
    sbi->s_group_desc = ext4_kvmalloc(db_count *
                      sizeof(struct buffer_head *),
                      GFP_KERNEL);
    if (sbi->s_group_desc == NULL) {
        ext4_msg(sb, KERN_ERR, "not enough memory");
        ret = -ENOMEM;
        goto failed_mount;
    }

    if (ext4_proc_root)
        sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root);

    if (sbi->s_proc)
        proc_create_data("options", S_IRUGO, sbi->s_proc,
                 &ext4_seq_options_fops, sb);

    bgl_lock_init(sbi->s_blockgroup_lock);

    for (i = 0; i < db_count; i++) {
        block = descriptor_loc(sb, logical_sb_block, i);
        sbi->s_group_desc[i] = sb_bread(sb, block);
        if (!sbi->s_group_desc[i]) {
            ext4_msg(sb, KERN_ERR,
                   "can't read group descriptor %d", i);
            db_count = i;
            goto failed_mount2;
        }
    }
    if (!ext4_check_descriptors(sb, &first_not_zeroed)) {
        ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
        goto failed_mount2;
    }
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
        if (!ext4_fill_flex_info(sb)) {
            ext4_msg(sb, KERN_ERR,
                   "unable to initialize "
                   "flex_bg meta info!");
            goto failed_mount2;
        }

    sbi->s_gdb_count = db_count;
    get_random_bytes(&sbi->s_next_generation, sizeof(u32));
    spin_lock_init(&sbi->s_next_gen_lock);

    init_timer(&sbi->s_err_report);
    sbi->s_err_report.function = print_daily_error_info;
    sbi->s_err_report.data = (unsigned long) sb;

    err = percpu_counter_init(&sbi->s_freeclusters_counter,
            ext4_count_free_clusters(sb));
    if (!err) {
        err = percpu_counter_init(&sbi->s_freeinodes_counter,
                ext4_count_free_inodes(sb));
    }
    if (!err) {
        err = percpu_counter_init(&sbi->s_dirs_counter,
                ext4_count_dirs(sb));
    }
    if (!err) {
        err = percpu_counter_init(&sbi->s_dirtyclusters_counter, 0);
    }
    if (err) {
        ext4_msg(sb, KERN_ERR, "insufficient memory");
        ret = err;
        goto failed_mount3;
    }

    sbi->s_stripe = ext4_get_stripe_size(sbi);
    sbi->s_max_writeback_mb_bump = 128;
    sbi->s_extent_max_zeroout_kb = 32;

    /*
     * set up enough so that it can read an inode
     */
    if (!test_opt(sb, NOLOAD) &&
        EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
        sb->s_op = &ext4_sops;
    else
        sb->s_op = &ext4_nojournal_sops;
    sb->s_export_op = &ext4_export_ops;
    sb->s_xattr = ext4_xattr_handlers;
#ifdef CONFIG_QUOTA
    sb->s_qcop = &ext4_qctl_operations;
    sb->dq_op = &ext4_quota_operations;

    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA)) {
        /* Use qctl operations for hidden quota files. */
        sb->s_qcop = &ext4_qctl_sysfile_operations;
    }
#endif
    memcpy(sb->s_uuid, es->s_uuid, sizeof(es->s_uuid));

    INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
    mutex_init(&sbi->s_orphan_lock);
    sbi->s_resize_flags = 0;

    sb->s_root = NULL;

    needs_recovery = (es->s_last_orphan != 0 ||
              EXT4_HAS_INCOMPAT_FEATURE(sb,
                    EXT4_FEATURE_INCOMPAT_RECOVER));

    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_MMP) &&
        !(sb->s_flags & MS_RDONLY))
        if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
            goto failed_mount3;

    /*
     * The first inode we look at is the journal inode.  Don't try
     * root first: it may be modified in the journal!
     */
    if (!test_opt(sb, NOLOAD) &&
        EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL)) {
        if (ext4_load_journal(sb, es, journal_devnum))
            goto failed_mount3;
    } else if (test_opt(sb, NOLOAD) && !(sb->s_flags & MS_RDONLY) &&
          EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER)) {
        ext4_msg(sb, KERN_ERR, "required journal recovery "
               "suppressed and not mounted read-only");
        goto failed_mount_wq;
    } else {
        clear_opt(sb, DATA_FLAGS);
        sbi->s_journal = NULL;
        needs_recovery = 0;
        goto no_journal;
    }

    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_64BIT) &&
        !jbd2_journal_set_features(EXT4_SB(sb)->s_journal, 0, 0,
                       JBD2_FEATURE_INCOMPAT_64BIT)) {
        ext4_msg(sb, KERN_ERR, "Failed to set 64-bit journal feature");
        goto failed_mount_wq;
    }

    if (!set_journal_csum_feature_set(sb)) {
        ext4_msg(sb, KERN_ERR, "Failed to set journal checksum "
             "feature set");
        goto failed_mount_wq;
    }

    /* We have now updated the journal if required, so we can
     * validate the data journaling mode. */
    switch (test_opt(sb, DATA_FLAGS)) {
    case 0:
        /* No mode set, assume a default based on the journal
         * capabilities: ORDERED_DATA if the journal can
         * cope, else JOURNAL_DATA
         */
        if (jbd2_journal_check_available_features
            (sbi->s_journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE))
            set_opt(sb, ORDERED_DATA);
        else
            set_opt(sb, JOURNAL_DATA);
        break;

    case EXT4_MOUNT_ORDERED_DATA:
    case EXT4_MOUNT_WRITEBACK_DATA:
        if (!jbd2_journal_check_available_features
            (sbi->s_journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE)) {
            ext4_msg(sb, KERN_ERR, "Journal does not support "
                   "requested data journaling mode");
            goto failed_mount_wq;
        }
    default:
        break;
    }
    set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);

    sbi->s_journal->j_commit_callback = ext4_journal_commit_callback;

    /*
     * The journal may have updated the bg summary counts, so we
     * need to update the global counters.
     */
    percpu_counter_set(&sbi->s_freeclusters_counter,
               ext4_count_free_clusters(sb));
    percpu_counter_set(&sbi->s_freeinodes_counter,
               ext4_count_free_inodes(sb));
    percpu_counter_set(&sbi->s_dirs_counter,
               ext4_count_dirs(sb));
    percpu_counter_set(&sbi->s_dirtyclusters_counter, 0);

no_journal:
    /*
     * Get the # of file system overhead blocks from the
     * superblock if present.
     */
    if (es->s_overhead_clusters)
        sbi->s_overhead = le32_to_cpu(es->s_overhead_clusters);
    else {
        ret = ext4_calculate_overhead(sb);
        if (ret)
            goto failed_mount_wq;
    }

    /*
     * The maximum number of concurrent works can be high and
     * concurrency isn't really necessary.  Limit it to 1.
     */
    EXT4_SB(sb)->dio_unwritten_wq =
        alloc_workqueue("ext4-dio-unwritten", WQ_MEM_RECLAIM | WQ_UNBOUND, 1);
    if (!EXT4_SB(sb)->dio_unwritten_wq) {
        printk(KERN_ERR "EXT4-fs: failed to create DIO workqueue\n");
        goto failed_mount_wq;
    }

    /*
     * The jbd2_journal_load will have done any necessary log recovery,
     * so we can safely mount the rest of the filesystem now.
     */

    root = ext4_iget(sb, EXT4_ROOT_INO);
    if (IS_ERR(root)) {
        ext4_msg(sb, KERN_ERR, "get root inode failed");
        ret = PTR_ERR(root);
        root = NULL;
        goto failed_mount4;
    }
    if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
        ext4_msg(sb, KERN_ERR, "corrupt root inode, run e2fsck");
        iput(root);
        goto failed_mount4;
    }
    sb->s_root = d_make_root(root);
    if (!sb->s_root) {
        ext4_msg(sb, KERN_ERR, "get root dentry failed");
        ret = -ENOMEM;
        goto failed_mount4;
    }

    if (ext4_setup_super(sb, es, sb->s_flags & MS_RDONLY))
        sb->s_flags |= MS_RDONLY;

    /* determine the minimum size of new large inodes, if present */
    if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
        sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
                             EXT4_GOOD_OLD_INODE_SIZE;
        if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
                       EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE)) {
            if (sbi->s_want_extra_isize <
                le16_to_cpu(es->s_want_extra_isize))
                sbi->s_want_extra_isize =
                    le16_to_cpu(es->s_want_extra_isize);
            if (sbi->s_want_extra_isize <
                le16_to_cpu(es->s_min_extra_isize))
                sbi->s_want_extra_isize =
                    le16_to_cpu(es->s_min_extra_isize);
        }
    }
    /* Check if enough inode space is available */
    if (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
                            sbi->s_inode_size) {
        sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
                               EXT4_GOOD_OLD_INODE_SIZE;
        ext4_msg(sb, KERN_INFO, "required extra inode space not"
             "available");
    }

    err = ext4_setup_system_zone(sb);
    if (err) {
        ext4_msg(sb, KERN_ERR, "failed to initialize system "
             "zone (%d)", err);
        goto failed_mount4a;
    }

    ext4_ext_init(sb);
    err = ext4_mb_init(sb);
    if (err) {
        ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
             err);
        goto failed_mount5;
    }

    err = ext4_register_li_request(sb, first_not_zeroed);
    if (err)
        goto failed_mount6;

    sbi->s_kobj.kset = ext4_kset;
    init_completion(&sbi->s_kobj_unregister);
    err = kobject_init_and_add(&sbi->s_kobj, &ext4_ktype, NULL,
                   "%s", sb->s_id);
    if (err)
        goto failed_mount7;

    EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
    ext4_orphan_cleanup(sb, es);
    EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
    if (needs_recovery) {
        ext4_msg(sb, KERN_INFO, "recovery complete");
        ext4_mark_recovery_complete(sb, es);
    }
    if (EXT4_SB(sb)->s_journal) {
        if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
            descr = " journalled data mode";
        else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA)
            descr = " ordered data mode";
        else
            descr = " writeback data mode";
    } else
        descr = "out journal";

#ifdef CONFIG_QUOTA
    /* Enable quota usage during mount. */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA) &&
        !(sb->s_flags & MS_RDONLY)) {
        ret = ext4_enable_quotas(sb);
        if (ret)
            goto failed_mount7;
    }
#endif  /* CONFIG_QUOTA */

    ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
         "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts,
         *sbi->s_es->s_mount_opts ? "; " : "", orig_data);

    if (es->s_error_count)
        mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */

    kfree(orig_data);
    return 0;

cantfind_ext4:
    if (!silent)
        ext4_msg(sb, KERN_ERR, "VFS: Can't find ext4 filesystem");
    goto failed_mount;

failed_mount7:
    ext4_unregister_li_request(sb);
failed_mount6:
    ext4_mb_release(sb);
failed_mount5:
    ext4_ext_release(sb);
    ext4_release_system_zone(sb);
failed_mount4a:
    dput(sb->s_root);
    sb->s_root = NULL;
failed_mount4:
    ext4_msg(sb, KERN_ERR, "mount failed");
    destroy_workqueue(EXT4_SB(sb)->dio_unwritten_wq);
failed_mount_wq:
    if (sbi->s_journal) {
        jbd2_journal_destroy(sbi->s_journal);
        sbi->s_journal = NULL;
    }
failed_mount3:
    del_timer(&sbi->s_err_report);
    if (sbi->s_flex_groups)
        ext4_kvfree(sbi->s_flex_groups);
    percpu_counter_destroy(&sbi->s_freeclusters_counter);
    percpu_counter_destroy(&sbi->s_freeinodes_counter);
    percpu_counter_destroy(&sbi->s_dirs_counter);
    percpu_counter_destroy(&sbi->s_dirtyclusters_counter);
    if (sbi->s_mmp_tsk)
        kthread_stop(sbi->s_mmp_tsk);
failed_mount2:
    for (i = 0; i < db_count; i++)
        brelse(sbi->s_group_desc[i]);
    ext4_kvfree(sbi->s_group_desc);
failed_mount:
    if (sbi->s_chksum_driver)
        crypto_free_shash(sbi->s_chksum_driver);
    if (sbi->s_proc) {
        remove_proc_entry("options", sbi->s_proc);
        remove_proc_entry(sb->s_id, ext4_proc_root);
    }
#ifdef CONFIG_QUOTA
    for (i = 0; i < MAXQUOTAS; i++)
        kfree(sbi->s_qf_names[i]);
#endif
    ext4_blkdev_remove(sbi);
    brelse(bh);
out_fail:
    sb->s_fs_info = NULL;
    kfree(sbi->s_blockgroup_lock);
    kfree(sbi);
out_free_orig:
    kfree(orig_data);
    return ret;
}

/*
 * Setup any per-fs journal parameters now.  We'll do this both on
 * initial mount, once the journal has been initialised but before we've
 * done any recovery; and again on any subsequent remount.
 */
static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
{
    struct ext4_sb_info *sbi = EXT4_SB(sb);

    journal->j_commit_interval = sbi->s_commit_interval;
    journal->j_min_batch_time = sbi->s_min_batch_time;
    journal->j_max_batch_time = sbi->s_max_batch_time;

    write_lock(&journal->j_state_lock);
    if (test_opt(sb, BARRIER))
        journal->j_flags |= JBD2_BARRIER;
    else
        journal->j_flags &= ~JBD2_BARRIER;
    if (test_opt(sb, DATA_ERR_ABORT))
        journal->j_flags |= JBD2_ABORT_ON_SYNCDATA_ERR;
    else
        journal->j_flags &= ~JBD2_ABORT_ON_SYNCDATA_ERR;
    write_unlock(&journal->j_state_lock);
}

static journal_t *ext4_get_journal(struct super_block *sb,
                   unsigned int journal_inum)
{
    struct inode *journal_inode;
    journal_t *journal;

    BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

    /* First, test for the existence of a valid inode on disk.  Bad
     * things happen if we iget() an unused inode, as the subsequent
     * iput() will try to delete it. */

    journal_inode = ext4_iget(sb, journal_inum);
    if (IS_ERR(journal_inode)) {
        ext4_msg(sb, KERN_ERR, "no journal found");
        return NULL;
    }
    if (!journal_inode->i_nlink) {
        make_bad_inode(journal_inode);
        iput(journal_inode);
        ext4_msg(sb, KERN_ERR, "journal inode is deleted");
        return NULL;
    }

    jbd_debug(2, "Journal inode found at %p: %lld bytes\n",
          journal_inode, journal_inode->i_size);
    if (!S_ISREG(journal_inode->i_mode)) {
        ext4_msg(sb, KERN_ERR, "invalid journal inode");
        iput(journal_inode);
        return NULL;
    }

    journal = jbd2_journal_init_inode(journal_inode);
    if (!journal) {
        ext4_msg(sb, KERN_ERR, "Could not load journal inode");
        iput(journal_inode);
        return NULL;
    }
    journal->j_private = sb;
    ext4_init_journal_params(sb, journal);
    return journal;
}

static journal_t *ext4_get_dev_journal(struct super_block *sb,
                       dev_t j_dev)
{
    struct buffer_head *bh;
    journal_t *journal;
    ext4_fsblk_t start;
    ext4_fsblk_t len;
    int hblock, blocksize;
    ext4_fsblk_t sb_block;
    unsigned long offset;
    struct ext4_super_block *es;
    struct block_device *bdev;

    BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

    bdev = ext4_blkdev_get(j_dev, sb);
    if (bdev == NULL)
        return NULL;

    blocksize = sb->s_blocksize;
    hblock = bdev_logical_block_size(bdev);
    if (blocksize < hblock) {
        ext4_msg(sb, KERN_ERR,
            "blocksize too small for journal device");
        goto out_bdev;
    }

    sb_block = EXT4_MIN_BLOCK_SIZE / blocksize;
    offset = EXT4_MIN_BLOCK_SIZE % blocksize;
    set_blocksize(bdev, blocksize);
    if (!(bh = __bread(bdev, sb_block, blocksize))) {
        ext4_msg(sb, KERN_ERR, "couldn't read superblock of "
               "external journal");
        goto out_bdev;
    }

    es = (struct ext4_super_block *) (bh->b_data + offset);
    if ((le16_to_cpu(es->s_magic) != EXT4_SUPER_MAGIC) ||
        !(le32_to_cpu(es->s_feature_incompat) &
          EXT4_FEATURE_INCOMPAT_JOURNAL_DEV)) {
        ext4_msg(sb, KERN_ERR, "external journal has "
                    "bad superblock");
        brelse(bh);
        goto out_bdev;
    }

    if (memcmp(EXT4_SB(sb)->s_es->s_journal_uuid, es->s_uuid, 16)) {
        ext4_msg(sb, KERN_ERR, "journal UUID does not match");
        brelse(bh);
        goto out_bdev;
    }

    len = ext4_blocks_count(es);
    start = sb_block + 1;
    brelse(bh); /* we're done with the superblock */

    journal = jbd2_journal_init_dev(bdev, sb->s_bdev,
                    start, len, blocksize);
    if (!journal) {
        ext4_msg(sb, KERN_ERR, "failed to create device journal");
        goto out_bdev;
    }
    journal->j_private = sb;
    ll_rw_block(READ, 1, &journal->j_sb_buffer);
    wait_on_buffer(journal->j_sb_buffer);
    if (!buffer_uptodate(journal->j_sb_buffer)) {
        ext4_msg(sb, KERN_ERR, "I/O error on journal device");
        goto out_journal;
    }
    if (be32_to_cpu(journal->j_superblock->s_nr_users) != 1) {
        ext4_msg(sb, KERN_ERR, "External journal has more than one "
                    "user (unsupported) - %d",
            be32_to_cpu(journal->j_superblock->s_nr_users));
        goto out_journal;
    }
    EXT4_SB(sb)->journal_bdev = bdev;
    ext4_init_journal_params(sb, journal);
    return journal;

out_journal:
    jbd2_journal_destroy(journal);
out_bdev:
    ext4_blkdev_put(bdev);
    return NULL;
}

static int ext4_load_journal(struct super_block *sb,
                 struct ext4_super_block *es,
                 unsigned long journal_devnum)
{
    journal_t *journal;
    unsigned int journal_inum = le32_to_cpu(es->s_journal_inum);
    dev_t journal_dev;
    int err = 0;
    int really_read_only;

    BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

    if (journal_devnum &&
        journal_devnum != le32_to_cpu(es->s_journal_dev)) {
        ext4_msg(sb, KERN_INFO, "external journal device major/minor "
            "numbers have changed");
        journal_dev = new_decode_dev(journal_devnum);
    } else
        journal_dev = new_decode_dev(le32_to_cpu(es->s_journal_dev));

    really_read_only = bdev_read_only(sb->s_bdev);

    /*
     * Are we loading a blank journal or performing recovery after a
     * crash?  For recovery, we need to check in advance whether we
     * can get read-write access to the device.
     */
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER)) {
        if (sb->s_flags & MS_RDONLY) {
            ext4_msg(sb, KERN_INFO, "INFO: recovery "
                    "required on readonly filesystem");
            if (really_read_only) {
                ext4_msg(sb, KERN_ERR, "write access "
                    "unavailable, cannot proceed");
                return -EROFS;
            }
            ext4_msg(sb, KERN_INFO, "write access will "
                   "be enabled during recovery");
        }
    }

    if (journal_inum && journal_dev) {
        ext4_msg(sb, KERN_ERR, "filesystem has both journal "
               "and inode journals!");
        return -EINVAL;
    }

    if (journal_inum) {
        if (!(journal = ext4_get_journal(sb, journal_inum)))
            return -EINVAL;
    } else {
        if (!(journal = ext4_get_dev_journal(sb, journal_dev)))
            return -EINVAL;
    }

    if (!(journal->j_flags & JBD2_BARRIER))
        ext4_msg(sb, KERN_INFO, "barriers disabled");

    if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER))
        err = jbd2_journal_wipe(journal, !really_read_only);
    if (!err) {
        char *save = kmalloc(EXT4_S_ERR_LEN, GFP_KERNEL);
        if (save)
            memcpy(save, ((char *) es) +
                   EXT4_S_ERR_START, EXT4_S_ERR_LEN);
        err = jbd2_journal_load(journal);
        if (save)
            memcpy(((char *) es) + EXT4_S_ERR_START,
                   save, EXT4_S_ERR_LEN);
        kfree(save);
    }

    if (err) {
        ext4_msg(sb, KERN_ERR, "error loading journal");
        jbd2_journal_destroy(journal);
        return err;
    }

    EXT4_SB(sb)->s_journal = journal;
    ext4_clear_journal_err(sb, es);

    if (!really_read_only && journal_devnum &&
        journal_devnum != le32_to_cpu(es->s_journal_dev)) {
        es->s_journal_dev = cpu_to_le32(journal_devnum);

        /* Make sure we flush the recovery flag to disk. */
        ext4_commit_super(sb, 1);
    }

    return 0;
}

static int ext4_commit_super(struct super_block *sb, int sync)
{
    struct ext4_super_block *es = EXT4_SB(sb)->s_es;
    struct buffer_head *sbh = EXT4_SB(sb)->s_sbh;
    int error = 0;

    if (!sbh || block_device_ejected(sb))
        return error;
    if (buffer_write_io_error(sbh)) {
        /*
         * Oh, dear.  A previous attempt to write the
         * superblock failed.  This could happen because the
         * USB device was yanked out.  Or it could happen to
         * be a transient write error and maybe the block will
         * be remapped.  Nothing we can do but to retry the
         * write and hope for the best.
         */
        ext4_msg(sb, KERN_ERR, "previous I/O error to "
               "superblock detected");
        clear_buffer_write_io_error(sbh);
        set_buffer_uptodate(sbh);
    }
    /*
     * If the file system is mounted read-only, don't update the
     * superblock write time.  This avoids updating the superblock
     * write time when we are mounting the root file system
     * read/only but we need to replay the journal; at that point,
     * for people who are east of GMT and who make their clock
     * tick in localtime for Windows bug-for-bug compatibility,
     * the clock is set in the future, and this will cause e2fsck
     * to complain and force a full file system check.
     */
    if (!(sb->s_flags & MS_RDONLY))
        es->s_wtime = cpu_to_le32(get_seconds());
    if (sb->s_bdev->bd_part)
        es->s_kbytes_written =
            cpu_to_le64(EXT4_SB(sb)->s_kbytes_written +
                ((part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
                  EXT4_SB(sb)->s_sectors_written_start) >> 1));
    else
        es->s_kbytes_written =
            cpu_to_le64(EXT4_SB(sb)->s_kbytes_written);
    ext4_free_blocks_count_set(es,
            EXT4_C2B(EXT4_SB(sb), percpu_counter_sum_positive(
                &EXT4_SB(sb)->s_freeclusters_counter)));
    es->s_free_inodes_count =
        cpu_to_le32(percpu_counter_sum_positive(
                &EXT4_SB(sb)->s_freeinodes_counter));
    BUFFER_TRACE(sbh, "marking dirty");
    ext4_superblock_csum_set(sb);
    mark_buffer_dirty(sbh);
    if (sync) {
        error = sync_dirty_buffer(sbh);
        if (error)
            return error;

        error = buffer_write_io_error(sbh);
        if (error) {
            ext4_msg(sb, KERN_ERR, "I/O error while writing "
                   "superblock");
            clear_buffer_write_io_error(sbh);
            set_buffer_uptodate(sbh);
        }
    }
    return error;
}

/*
 * Have we just finished recovery?  If so, and if we are mounting (or
 * remounting) the filesystem readonly, then we will end up with a
 * consistent fs on disk.  Record that fact.
 */
static void ext4_mark_recovery_complete(struct super_block *sb,
                    struct ext4_super_block *es)
{
    journal_t *journal = EXT4_SB(sb)->s_journal;

    if (!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL)) {
        BUG_ON(journal != NULL);
        return;
    }
    jbd2_journal_lock_updates(journal);
    if (jbd2_journal_flush(journal) < 0)
        goto out;

    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER) &&
        sb->s_flags & MS_RDONLY) {
        EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
        ext4_commit_super(sb, 1);
    }

out:
    jbd2_journal_unlock_updates(journal);
}

/*
 * If we are mounting (or read-write remounting) a filesystem whose journal
 * has recorded an error from a previous lifetime, move that error to the
 * main filesystem now.
 */
static void ext4_clear_journal_err(struct super_block *sb,
                   struct ext4_super_block *es)
{
    journal_t *journal;
    int j_errno;
    const char *errstr;

    BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

    journal = EXT4_SB(sb)->s_journal;

    /*
     * Now check for any error status which may have been recorded in the
     * journal by a prior ext4_error() or ext4_abort()
     */

    j_errno = jbd2_journal_errno(journal);
    if (j_errno) {
        char nbuf[16];

        errstr = ext4_decode_error(sb, j_errno, nbuf);
        ext4_warning(sb, "Filesystem error recorded "
                 "from previous mount: %s", errstr);
        ext4_warning(sb, "Marking fs in need of filesystem check.");

        EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
        es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
        ext4_commit_super(sb, 1);

        jbd2_journal_clear_err(journal);
        jbd2_journal_update_sb_errno(journal);
    }
}

/*
 * Force the running and committing transactions to commit,
 * and wait on the commit.
 */
int ext4_force_commit(struct super_block *sb)
{
    journal_t *journal;
    int ret = 0;

    if (sb->s_flags & MS_RDONLY)
        return 0;

    journal = EXT4_SB(sb)->s_journal;
    if (journal)
        ret = ext4_journal_force_commit(journal);

    return ret;
}

static int ext4_sync_fs(struct super_block *sb, int wait)
{
    int ret = 0;
    tid_t target;
    struct ext4_sb_info *sbi = EXT4_SB(sb);

    trace_ext4_sync_fs(sb, wait);
    flush_workqueue(sbi->dio_unwritten_wq);
    /*
     * Writeback quota in non-journalled quota case - journalled quota has
     * no dirty dquots
     */
    dquot_writeback_dquots(sb, -1);
    if (jbd2_journal_start_commit(sbi->s_journal, &target)) {
        if (wait)
            jbd2_log_wait_commit(sbi->s_journal, target);
    }
    return ret;
}

/*
 * LVM calls this function before a (read-only) snapshot is created.  This
 * gives us a chance to flush the journal completely and mark the fs clean.
 *
 * Note that only this function cannot bring a filesystem to be in a clean
 * state independently. It relies on upper layer to stop all data & metadata
 * modifications.
 */
static int ext4_freeze(struct super_block *sb)
{
    int error = 0;
    journal_t *journal;

    if (sb->s_flags & MS_RDONLY)
        return 0;

    journal = EXT4_SB(sb)->s_journal;

    /* Now we set up the journal barrier. */
    jbd2_journal_lock_updates(journal);

    /*
     * Don't clear the needs_recovery flag if we failed to flush
     * the journal.
     */
    error = jbd2_journal_flush(journal);
    if (error < 0)
        goto out;

    /* Journal blocked and flushed, clear needs_recovery flag. */
    EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
    error = ext4_commit_super(sb, 1);
out:
    /* we rely on upper layer to stop further updates */
    jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
    return error;
}

/*
 * Called by LVM after the snapshot is done.  We need to reset the RECOVER
 * flag here, even though the filesystem is not technically dirty yet.
 */
static int ext4_unfreeze(struct super_block *sb)
{
    if (sb->s_flags & MS_RDONLY)
        return 0;

    /* Reset the needs_recovery flag before the fs is unlocked. */
    EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
    ext4_commit_super(sb, 1);
    return 0;
}

/*
 * Structure to save mount options for ext4_remount's benefit
 */
struct ext4_mount_options {
    unsigned long s_mount_opt;
    unsigned long s_mount_opt2;
    kuid_t s_resuid;
    kgid_t s_resgid;
    unsigned long s_commit_interval;
    u32 s_min_batch_time, s_max_batch_time;
#ifdef CONFIG_QUOTA
    int s_jquota_fmt;
    char *s_qf_names[MAXQUOTAS];
#endif
};

static int ext4_remount(struct super_block *sb, int *flags, char *data)
{
    struct ext4_super_block *es;
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    unsigned long old_sb_flags;
    struct ext4_mount_options old_opts;
    int enable_quota = 0;
    ext4_group_t g;
    unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
    int err = 0;
#ifdef CONFIG_QUOTA
    int i;
#endif
    char *orig_data = kstrdup(data, GFP_KERNEL);

    /* Store the original options */
    old_sb_flags = sb->s_flags;
    old_opts.s_mount_opt = sbi->s_mount_opt;
    old_opts.s_mount_opt2 = sbi->s_mount_opt2;
    old_opts.s_resuid = sbi->s_resuid;
    old_opts.s_resgid = sbi->s_resgid;
    old_opts.s_commit_interval = sbi->s_commit_interval;
    old_opts.s_min_batch_time = sbi->s_min_batch_time;
    old_opts.s_max_batch_time = sbi->s_max_batch_time;
#ifdef CONFIG_QUOTA
    old_opts.s_jquota_fmt = sbi->s_jquota_fmt;
    for (i = 0; i < MAXQUOTAS; i++)
        old_opts.s_qf_names[i] = sbi->s_qf_names[i];
#endif
    if (sbi->s_journal && sbi->s_journal->j_task->io_context)
        journal_ioprio = sbi->s_journal->j_task->io_context->ioprio;

    /*
     * Allow the "check" option to be passed as a remount option.
     */
    if (!parse_options(data, sb, NULL, &journal_ioprio, 1)) {
        err = -EINVAL;
        goto restore_opts;
    }

    if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
        ext4_abort(sb, "Abort forced by user");

    sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
        (test_opt(sb, POSIX_ACL) ? MS_POSIXACL : 0);

    es = sbi->s_es;

    if (sbi->s_journal) {
        ext4_init_journal_params(sb, sbi->s_journal);
        set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
    }

    if ((*flags & MS_RDONLY) != (sb->s_flags & MS_RDONLY)) {
        if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED) {
            err = -EROFS;
            goto restore_opts;
        }

        if (*flags & MS_RDONLY) {
            err = dquot_suspend(sb, -1);
            if (err < 0)
                goto restore_opts;

            /*
             * First of all, the unconditional stuff we have to do
             * to disable replay of the journal when we next remount
             */
            sb->s_flags |= MS_RDONLY;

            /*
             * OK, test if we are remounting a valid rw partition
             * readonly, and if so set the rdonly flag and then
             * mark the partition as valid again.
             */
            if (!(es->s_state & cpu_to_le16(EXT4_VALID_FS)) &&
                (sbi->s_mount_state & EXT4_VALID_FS))
                es->s_state = cpu_to_le16(sbi->s_mount_state);

            if (sbi->s_journal)
                ext4_mark_recovery_complete(sb, es);
        } else {
            /* Make sure we can mount this feature set readwrite */
            if (!ext4_feature_set_ok(sb, 0)) {
                err = -EROFS;
                goto restore_opts;
            }
            /*
             * Make sure the group descriptor checksums
             * are sane.  If they aren't, refuse to remount r/w.
             */
            for (g = 0; g < sbi->s_groups_count; g++) {
                struct ext4_group_desc *gdp =
                    ext4_get_group_desc(sb, g, NULL);

                if (!ext4_group_desc_csum_verify(sb, g, gdp)) {
                    ext4_msg(sb, KERN_ERR,
           "ext4_remount: Checksum for group %u failed (%u!=%u)",
        g, le16_to_cpu(ext4_group_desc_csum(sbi, g, gdp)),
                           le16_to_cpu(gdp->bg_checksum));
                    err = -EINVAL;
                    goto restore_opts;
                }
            }

            /*
             * If we have an unprocessed orphan list hanging
             * around from a previously readonly bdev mount,
             * require a full umount/remount for now.
             */
            if (es->s_last_orphan) {
                ext4_msg(sb, KERN_WARNING, "Couldn't "
                       "remount RDWR because of unprocessed "
                       "orphan inode list.  Please "
                       "umount/remount instead");
                err = -EINVAL;
                goto restore_opts;
            }

            /*
             * Mounting a RDONLY partition read-write, so reread
             * and store the current valid flag.  (It may have
             * been changed by e2fsck since we originally mounted
             * the partition.)
             */
            if (sbi->s_journal)
                ext4_clear_journal_err(sb, es);
            sbi->s_mount_state = le16_to_cpu(es->s_state);
            if (!ext4_setup_super(sb, es, 0))
                sb->s_flags &= ~MS_RDONLY;
            if (EXT4_HAS_INCOMPAT_FEATURE(sb,
                             EXT4_FEATURE_INCOMPAT_MMP))
                if (ext4_multi_mount_protect(sb,
                        le64_to_cpu(es->s_mmp_block))) {
                    err = -EROFS;
                    goto restore_opts;
                }
            enable_quota = 1;
        }
    }

    /*
     * Reinitialize lazy itable initialization thread based on
     * current settings
     */
    if ((sb->s_flags & MS_RDONLY) || !test_opt(sb, INIT_INODE_TABLE))
        ext4_unregister_li_request(sb);
    else {
        ext4_group_t first_not_zeroed;
        first_not_zeroed = ext4_has_uninit_itable(sb);
        ext4_register_li_request(sb, first_not_zeroed);
    }

    ext4_setup_system_zone(sb);
    if (sbi->s_journal == NULL)
        ext4_commit_super(sb, 1);

#ifdef CONFIG_QUOTA
    /* Release old quota file names */
    for (i = 0; i < MAXQUOTAS; i++)
        if (old_opts.s_qf_names[i] &&
            old_opts.s_qf_names[i] != sbi->s_qf_names[i])
            kfree(old_opts.s_qf_names[i]);
    if (enable_quota) {
        if (sb_any_quota_suspended(sb))
            dquot_resume(sb, -1);
        else if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
                    EXT4_FEATURE_RO_COMPAT_QUOTA)) {
            err = ext4_enable_quotas(sb);
            if (err)
                goto restore_opts;
        }
    }
#endif

    ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s", orig_data);
    kfree(orig_data);
    return 0;

restore_opts:
    sb->s_flags = old_sb_flags;
    sbi->s_mount_opt = old_opts.s_mount_opt;
    sbi->s_mount_opt2 = old_opts.s_mount_opt2;
    sbi->s_resuid = old_opts.s_resuid;
    sbi->s_resgid = old_opts.s_resgid;
    sbi->s_commit_interval = old_opts.s_commit_interval;
    sbi->s_min_batch_time = old_opts.s_min_batch_time;
    sbi->s_max_batch_time = old_opts.s_max_batch_time;
#ifdef CONFIG_QUOTA
    sbi->s_jquota_fmt = old_opts.s_jquota_fmt;
    for (i = 0; i < MAXQUOTAS; i++) {
        if (sbi->s_qf_names[i] &&
            old_opts.s_qf_names[i] != sbi->s_qf_names[i])
            kfree(sbi->s_qf_names[i]);
        sbi->s_qf_names[i] = old_opts.s_qf_names[i];
    }
#endif
    kfree(orig_data);
    return err;
}

static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
{
    struct super_block *sb = dentry->d_sb;
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_super_block *es = sbi->s_es;
    ext4_fsblk_t overhead = 0;
    u64 fsid;
    s64 bfree;

    if (!test_opt(sb, MINIX_DF))
        overhead = sbi->s_overhead;

    buf->f_type = EXT4_SUPER_MAGIC;
    buf->f_bsize = sb->s_blocksize;
    buf->f_blocks = ext4_blocks_count(es) - EXT4_C2B(sbi, sbi->s_overhead);
    bfree = percpu_counter_sum_positive(&sbi->s_freeclusters_counter) -
        percpu_counter_sum_positive(&sbi->s_dirtyclusters_counter);
    /* prevent underflow in case that few free space is available */
    buf->f_bfree = EXT4_C2B(sbi, max_t(s64, bfree, 0));
    buf->f_bavail = buf->f_bfree - ext4_r_blocks_count(es);
    if (buf->f_bfree < ext4_r_blocks_count(es))
        buf->f_bavail = 0;
    buf->f_files = le32_to_cpu(es->s_inodes_count);
    buf->f_ffree = percpu_counter_sum_positive(&sbi->s_freeinodes_counter);
    buf->f_namelen = EXT4_NAME_LEN;
    fsid = le64_to_cpup((void *)es->s_uuid) ^
           le64_to_cpup((void *)es->s_uuid + sizeof(u64));
    buf->f_fsid.val[0] = fsid & 0xFFFFFFFFUL;
    buf->f_fsid.val[1] = (fsid >> 32) & 0xFFFFFFFFUL;

    return 0;
}

/* Helper function for writing quotas on sync - we need to start transaction
 * before quota file is locked for write. Otherwise the are possible deadlocks:
 * Process 1                         Process 2
 * ext4_create()                     quota_sync()
 *   jbd2_journal_start()                  write_dquot()
 *   dquot_initialize()                         down(dqio_mutex)
 *     down(dqio_mutex)                    jbd2_journal_start()
 *
 */

#ifdef CONFIG_QUOTA

static inline struct inode *dquot_to_inode(struct dquot *dquot)
{
    return sb_dqopt(dquot->dq_sb)->files[dquot->dq_id.type];
}

static int ext4_write_dquot(struct dquot *dquot)
{
    int ret, err;
    handle_t *handle;
    struct inode *inode;

    inode = dquot_to_inode(dquot);
    handle = ext4_journal_start(inode,
                    EXT4_QUOTA_TRANS_BLOCKS(dquot->dq_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);
    ret = dquot_commit(dquot);
    err = ext4_journal_stop(handle);
    if (!ret)
        ret = err;
    return ret;
}

static int ext4_acquire_dquot(struct dquot *dquot)
{
    int ret, err;
    handle_t *handle;

    handle = ext4_journal_start(dquot_to_inode(dquot),
                    EXT4_QUOTA_INIT_BLOCKS(dquot->dq_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);
    ret = dquot_acquire(dquot);
    err = ext4_journal_stop(handle);
    if (!ret)
        ret = err;
    return ret;
}

static int ext4_release_dquot(struct dquot *dquot)
{
    int ret, err;
    handle_t *handle;

    handle = ext4_journal_start(dquot_to_inode(dquot),
                    EXT4_QUOTA_DEL_BLOCKS(dquot->dq_sb));
    if (IS_ERR(handle)) {
        /* Release dquot anyway to avoid endless cycle in dqput() */
        dquot_release(dquot);
        return PTR_ERR(handle);
    }
    ret = dquot_release(dquot);
    err = ext4_journal_stop(handle);
    if (!ret)
        ret = err;
    return ret;
}

static int ext4_mark_dquot_dirty(struct dquot *dquot)
{
    /* Are we journaling quotas? */
    if (EXT4_SB(dquot->dq_sb)->s_qf_names[USRQUOTA] ||
        EXT4_SB(dquot->dq_sb)->s_qf_names[GRPQUOTA]) {
        dquot_mark_dquot_dirty(dquot);
        return ext4_write_dquot(dquot);
    } else {
        return dquot_mark_dquot_dirty(dquot);
    }
}

static int ext4_write_info(struct super_block *sb, int type)
{
    int ret, err;
    handle_t *handle;

    /* Data block + inode block */
    handle = ext4_journal_start(sb->s_root->d_inode, 2);
    if (IS_ERR(handle))
        return PTR_ERR(handle);
    ret = dquot_commit_info(sb, type);
    err = ext4_journal_stop(handle);
    if (!ret)
        ret = err;
    return ret;
}

/*
 * Turn on quotas during mount time - we need to find
 * the quota file and such...
 */
static int ext4_quota_on_mount(struct super_block *sb, int type)
{
    return dquot_quota_on_mount(sb, EXT4_SB(sb)->s_qf_names[type],
                    EXT4_SB(sb)->s_jquota_fmt, type);
}

/*
 * Standard function to be called on quota_on
 */
static int ext4_quota_on(struct super_block *sb, int type, int format_id,
             struct path *path)
{
    int err;

    if (!test_opt(sb, QUOTA))
        return -EINVAL;

    /* Quotafile not on the same filesystem? */
    if (path->dentry->d_sb != sb)
        return -EXDEV;
    /* Journaling quota? */
    if (EXT4_SB(sb)->s_qf_names[type]) {
        /* Quotafile not in fs root? */
        if (path->dentry->d_parent != sb->s_root)
            ext4_msg(sb, KERN_WARNING,
                "Quota file not on filesystem root. "
                "Journaled quota will not work");
    }

    /*
     * When we journal data on quota file, we have to flush journal to see
     * all updates to the file when we bypass pagecache...
     */
    if (EXT4_SB(sb)->s_journal &&
        ext4_should_journal_data(path->dentry->d_inode)) {
        /*
         * We don't need to lock updates but journal_flush() could
         * otherwise be livelocked...
         */
        jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
        err = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
        jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
        if (err)
            return err;
    }

    return dquot_quota_on(sb, type, format_id, path);
}

static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
                 unsigned int flags)
{
    int err;
    struct inode *qf_inode;
    unsigned long qf_inums[MAXQUOTAS] = {
        le32_to_cpu(EXT4_SB(sb)->s_es->s_usr_quota_inum),
        le32_to_cpu(EXT4_SB(sb)->s_es->s_grp_quota_inum)
    };

    BUG_ON(!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA));

    if (!qf_inums[type])
        return -EPERM;

    qf_inode = ext4_iget(sb, qf_inums[type]);
    if (IS_ERR(qf_inode)) {
        ext4_error(sb, "Bad quota inode # %lu", qf_inums[type]);
        return PTR_ERR(qf_inode);
    }

    err = dquot_enable(qf_inode, type, format_id, flags);
    iput(qf_inode);

    return err;
}

/* Enable usage tracking for all quota types. */
static int ext4_enable_quotas(struct super_block *sb)
{
    int type, err = 0;
    unsigned long qf_inums[MAXQUOTAS] = {
        le32_to_cpu(EXT4_SB(sb)->s_es->s_usr_quota_inum),
        le32_to_cpu(EXT4_SB(sb)->s_es->s_grp_quota_inum)
    };

    sb_dqopt(sb)->flags |= DQUOT_QUOTA_SYS_FILE;
    for (type = 0; type < MAXQUOTAS; type++) {
        if (qf_inums[type]) {
            err = ext4_quota_enable(sb, type, QFMT_VFS_V1,
                        DQUOT_USAGE_ENABLED);
            if (err) {
                ext4_warning(sb,
                    "Failed to enable quota (type=%d) "
                    "tracking. Please run e2fsck to fix.",
                    type);
                return err;
            }
        }
    }
    return 0;
}

/*
 * quota_on function that is used when QUOTA feature is set.
 */
static int ext4_quota_on_sysfile(struct super_block *sb, int type,
                 int format_id)
{
    if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA))
        return -EINVAL;

    /*
     * USAGE was enabled at mount time. Only need to enable LIMITS now.
     */
    return ext4_quota_enable(sb, type, format_id, DQUOT_LIMITS_ENABLED);
}

static int ext4_quota_off(struct super_block *sb, int type)
{
    struct inode *inode = sb_dqopt(sb)->files[type];
    handle_t *handle;

    /* Force all delayed allocation blocks to be allocated.
     * Caller already holds s_umount sem */
    if (test_opt(sb, DELALLOC))
        sync_filesystem(sb);

    if (!inode)
        goto out;

    /* Update modification times of quota files when userspace can
     * start looking at them */
    handle = ext4_journal_start(inode, 1);
    if (IS_ERR(handle))
        goto out;
    inode->i_mtime = inode->i_ctime = CURRENT_TIME;
    ext4_mark_inode_dirty(handle, inode);
    ext4_journal_stop(handle);

out:
    return dquot_quota_off(sb, type);
}

/*
 * quota_off function that is used when QUOTA feature is set.
 */
static int ext4_quota_off_sysfile(struct super_block *sb, int type)
{
    if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_QUOTA))
        return -EINVAL;

    /* Disable only the limits. */
    return dquot_disable(sb, type, DQUOT_LIMITS_ENABLED);
}

/* Read data from quotafile - avoid pagecache and such because we cannot afford
 * acquiring the locks... As quota files are never truncated and quota code
 * itself serializes the operations (and no one else should touch the files)
 * we don't have to be afraid of races */
static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data,
                   size_t len, loff_t off)
{
    struct inode *inode = sb_dqopt(sb)->files[type];
    ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
    int err = 0;
    int offset = off & (sb->s_blocksize - 1);
    int tocopy;
    size_t toread;
    struct buffer_head *bh;
    loff_t i_size = i_size_read(inode);

    if (off > i_size)
        return 0;
    if (off+len > i_size)
        len = i_size-off;
    toread = len;
    while (toread > 0) {
        tocopy = sb->s_blocksize - offset < toread ?
                sb->s_blocksize - offset : toread;
        bh = ext4_bread(NULL, inode, blk, 0, &err);
        if (err)
            return err;
        if (!bh)    /* A hole? */
            memset(data, 0, tocopy);
        else
            memcpy(data, bh->b_data+offset, tocopy);
        brelse(bh);
        offset = 0;
        toread -= tocopy;
        data += tocopy;
        blk++;
    }
    return len;
}

/* Write to quotafile (we know the transaction is already started and has
 * enough credits) */
static ssize_t ext4_quota_write(struct super_block *sb, int type,
                const char *data, size_t len, loff_t off)
{
    struct inode *inode = sb_dqopt(sb)->files[type];
    ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
    int err = 0;
    int offset = off & (sb->s_blocksize - 1);
    struct buffer_head *bh;
    handle_t *handle = journal_current_handle();

    if (EXT4_SB(sb)->s_journal && !handle) {
        ext4_msg(sb, KERN_WARNING, "Quota write (off=%llu, len=%llu)"
            " cancelled because transaction is not started",
            (unsigned long long)off, (unsigned long long)len);
        return -EIO;
    }
    /*
     * Since we account only one data block in transaction credits,
     * then it is impossible to cross a block boundary.
     */
    if (sb->s_blocksize - offset < len) {
        ext4_msg(sb, KERN_WARNING, "Quota write (off=%llu, len=%llu)"
            " cancelled because not block aligned",
            (unsigned long long)off, (unsigned long long)len);
        return -EIO;
    }

    bh = ext4_bread(handle, inode, blk, 1, &err);
    if (!bh)
        goto out;
    err = ext4_journal_get_write_access(handle, bh);
    if (err) {
        brelse(bh);
        goto out;
    }
    lock_buffer(bh);
    memcpy(bh->b_data+offset, data, len);
    flush_dcache_page(bh->b_page);
    unlock_buffer(bh);
    err = ext4_handle_dirty_metadata(handle, NULL, bh);
    brelse(bh);
out:
    if (err)
        return err;
    if (inode->i_size < off + len) {
        i_size_write(inode, off + len);
        EXT4_I(inode)->i_disksize = inode->i_size;
        ext4_mark_inode_dirty(handle, inode);
    }
    return len;
}

#endif

static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags,
               const char *dev_name, void *data)
{
    return mount_bdev(fs_type, flags, dev_name, data, ext4_fill_super);
}

#if !defined(CONFIG_EXT2_FS) && !defined(CONFIG_EXT2_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
static inline void register_as_ext2(void)
{
    int err = register_filesystem(&ext2_fs_type);
    if (err)
        printk(KERN_WARNING
               "EXT4-fs: Unable to register as ext2 (%d)\n", err);
}

static inline void unregister_as_ext2(void)
{
    unregister_filesystem(&ext2_fs_type);
}

static inline int ext2_feature_set_ok(struct super_block *sb)
{
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP))
        return 0;
    if (sb->s_flags & MS_RDONLY)
        return 1;
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT2_FEATURE_RO_COMPAT_SUPP))
        return 0;
    return 1;
}
MODULE_ALIAS("ext2");
#else
static inline void register_as_ext2(void) { }
static inline void unregister_as_ext2(void) { }
static inline int ext2_feature_set_ok(struct super_block *sb) { return 0; }
#endif

#if !defined(CONFIG_EXT3_FS) && !defined(CONFIG_EXT3_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
static inline void register_as_ext3(void)
{
    int err = register_filesystem(&ext3_fs_type);
    if (err)
        printk(KERN_WARNING
               "EXT4-fs: Unable to register as ext3 (%d)\n", err);
}

static inline void unregister_as_ext3(void)
{
    unregister_filesystem(&ext3_fs_type);
}

static inline int ext3_feature_set_ok(struct super_block *sb)
{
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, ~EXT3_FEATURE_INCOMPAT_SUPP))
        return 0;
    if (!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
        return 0;
    if (sb->s_flags & MS_RDONLY)
        return 1;
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT3_FEATURE_RO_COMPAT_SUPP))
        return 0;
    return 1;
}
MODULE_ALIAS("ext3");
#else
static inline void register_as_ext3(void) { }
static inline void unregister_as_ext3(void) { }
static inline int ext3_feature_set_ok(struct super_block *sb) { return 0; }
#endif

static struct file_system_type ext4_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "ext4",
    .mount      = ext4_mount,
    .kill_sb    = kill_block_super,
    .fs_flags   = FS_REQUIRES_DEV,
};

static int __init ext4_init_feat_adverts(void)
{
    struct ext4_features *ef;
    int ret = -ENOMEM;

    ef = kzalloc(sizeof(struct ext4_features), GFP_KERNEL);
    if (!ef)
        goto out;

    ef->f_kobj.kset = ext4_kset;
    init_completion(&ef->f_kobj_unregister);
    ret = kobject_init_and_add(&ef->f_kobj, &ext4_feat_ktype, NULL,
                   "features");
    if (ret) {
        kfree(ef);
        goto out;
    }

    ext4_feat = ef;
    ret = 0;
out:
    return ret;
}

static void ext4_exit_feat_adverts(void)
{
    kobject_put(&ext4_feat->f_kobj);
    wait_for_completion(&ext4_feat->f_kobj_unregister);
    kfree(ext4_feat);
}

/* Shared across all ext4 file systems */
wait_queue_head_t ext4__ioend_wq[EXT4_WQ_HASH_SZ];
struct mutex ext4__aio_mutex[EXT4_WQ_HASH_SZ];

static int __init ext4_init_fs(void)
{
    int i, err;

    ext4_li_info = NULL;
    mutex_init(&ext4_li_mtx);

    ext4_check_flag_values();

    for (i = 0; i < EXT4_WQ_HASH_SZ; i++) {
        mutex_init(&ext4__aio_mutex[i]);
        init_waitqueue_head(&ext4__ioend_wq[i]);
    }

    err = ext4_init_pageio();
    if (err)
        return err;
    err = ext4_init_system_zone();
    if (err)
        goto out6;
    ext4_kset = kset_create_and_add("ext4", NULL, fs_kobj);
    if (!ext4_kset) {
        err = -ENOMEM;
        goto out5;
    }
    ext4_proc_root = proc_mkdir("fs/ext4", NULL);

    err = ext4_init_feat_adverts();
    if (err)
        goto out4;

    err = ext4_init_mballoc();
    if (err)
        goto out3;

    err = ext4_init_xattr();
    if (err)
        goto out2;
    err = init_inodecache();
    if (err)
        goto out1;
    register_as_ext3();
    register_as_ext2();
    err = register_filesystem(&ext4_fs_type);
    if (err)
        goto out;

    return 0;
out:
    unregister_as_ext2();
    unregister_as_ext3();
    destroy_inodecache();
out1:
    ext4_exit_xattr();
out2:
    ext4_exit_mballoc();
out3:
    ext4_exit_feat_adverts();
out4:
    if (ext4_proc_root)
        remove_proc_entry("fs/ext4", NULL);
    kset_unregister(ext4_kset);
out5:
    ext4_exit_system_zone();
out6:
    ext4_exit_pageio();
    return err;
}

static void __exit ext4_exit_fs(void)
{
    ext4_destroy_lazyinit_thread();
    unregister_as_ext2();
    unregister_as_ext3();
    unregister_filesystem(&ext4_fs_type);
    destroy_inodecache();
    ext4_exit_xattr();
    ext4_exit_mballoc();
    ext4_exit_feat_adverts();
    remove_proc_entry("fs/ext4", NULL);
    kset_unregister(ext4_kset);
    ext4_exit_system_zone();
    ext4_exit_pageio();
}

MODULE_AUTHOR("Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others");
MODULE_DESCRIPTION("Fourth Extended Filesystem");
MODULE_LICENSE("GPL");
module_init(ext4_init_fs)
module_exit(ext4_exit_fs)