ialloc.c

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/*
 *  linux/fs/ext4/ialloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  BSD ufs-inspired inode and directory allocation by
 *  Stephen Tweedie ([email protected]), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd2.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/random.h>
#include <linux/bitops.h>
#include <linux/blkdev.h>
#include <asm/byteorder.h>

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

#include <trace/events/ext4.h>

/*
 * ialloc.c contains the inodes allocation and deallocation routines
 */

/*
 * The free inodes are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.
 */

/*
 * To avoid calling the atomic setbit hundreds or thousands of times, we only
 * need to use it within a single byte (to ensure we get endianness right).
 * We can use memset for the rest of the bitmap as there are no other users.
 */
void ext4_mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
{
    int i;

    if (start_bit >= end_bit)
        return;

    ext4_debug("mark end bits +%d through +%d used\n", start_bit, end_bit);
    for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
        ext4_set_bit(i, bitmap);
    if (i < end_bit)
        memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
}

/* Initializes an uninitialized inode bitmap */
static unsigned ext4_init_inode_bitmap(struct super_block *sb,
                       struct buffer_head *bh,
                       ext4_group_t block_group,
                       struct ext4_group_desc *gdp)
{
    J_ASSERT_BH(bh, buffer_locked(bh));

    /* If checksum is bad mark all blocks and inodes use to prevent
     * allocation, essentially implementing a per-group read-only flag. */
    if (!ext4_group_desc_csum_verify(sb, block_group, gdp)) {
        ext4_error(sb, "Checksum bad for group %u", block_group);
        ext4_free_group_clusters_set(sb, gdp, 0);
        ext4_free_inodes_set(sb, gdp, 0);
        ext4_itable_unused_set(sb, gdp, 0);
        memset(bh->b_data, 0xff, sb->s_blocksize);
        ext4_inode_bitmap_csum_set(sb, block_group, gdp, bh,
                       EXT4_INODES_PER_GROUP(sb) / 8);
        return 0;
    }

    memset(bh->b_data, 0, (EXT4_INODES_PER_GROUP(sb) + 7) / 8);
    ext4_mark_bitmap_end(EXT4_INODES_PER_GROUP(sb), sb->s_blocksize * 8,
            bh->b_data);
    ext4_inode_bitmap_csum_set(sb, block_group, gdp, bh,
                   EXT4_INODES_PER_GROUP(sb) / 8);
    ext4_group_desc_csum_set(sb, block_group, gdp);

    return EXT4_INODES_PER_GROUP(sb);
}

void ext4_end_bitmap_read(struct buffer_head *bh, int uptodate)
{
    if (uptodate) {
        set_buffer_uptodate(bh);
        set_bitmap_uptodate(bh);
    }
    unlock_buffer(bh);
    put_bh(bh);
}

/*
 * Read the inode allocation bitmap for a given block_group, reading
 * into the specified slot in the superblock's bitmap cache.
 *
 * Return buffer_head of bitmap on success or NULL.
 */
static struct buffer_head *
ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
{
    struct ext4_group_desc *desc;
    struct buffer_head *bh = NULL;
    ext4_fsblk_t bitmap_blk;

    desc = ext4_get_group_desc(sb, block_group, NULL);
    if (!desc)
        return NULL;

    bitmap_blk = ext4_inode_bitmap(sb, desc);
    bh = sb_getblk(sb, bitmap_blk);
    if (unlikely(!bh)) {
        ext4_error(sb, "Cannot read inode bitmap - "
                "block_group = %u, inode_bitmap = %llu",
                block_group, bitmap_blk);
        return NULL;
    }
    if (bitmap_uptodate(bh))
        goto verify;

    lock_buffer(bh);
    if (bitmap_uptodate(bh)) {
        unlock_buffer(bh);
        goto verify;
    }

    ext4_lock_group(sb, block_group);
    if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
        ext4_init_inode_bitmap(sb, bh, block_group, desc);
        set_bitmap_uptodate(bh);
        set_buffer_uptodate(bh);
        set_buffer_verified(bh);
        ext4_unlock_group(sb, block_group);
        unlock_buffer(bh);
        return bh;
    }
    ext4_unlock_group(sb, block_group);

    if (buffer_uptodate(bh)) {
        /*
         * if not uninit if bh is uptodate,
         * bitmap is also uptodate
         */
        set_bitmap_uptodate(bh);
        unlock_buffer(bh);
        goto verify;
    }
    /*
     * submit the buffer_head for reading
     */
    trace_ext4_load_inode_bitmap(sb, block_group);
    bh->b_end_io = ext4_end_bitmap_read;
    get_bh(bh);
    submit_bh(READ, bh);
    wait_on_buffer(bh);
    if (!buffer_uptodate(bh)) {
        put_bh(bh);
        ext4_error(sb, "Cannot read inode bitmap - "
               "block_group = %u, inode_bitmap = %llu",
               block_group, bitmap_blk);
        return NULL;
    }

verify:
    ext4_lock_group(sb, block_group);
    if (!buffer_verified(bh) &&
        !ext4_inode_bitmap_csum_verify(sb, block_group, desc, bh,
                       EXT4_INODES_PER_GROUP(sb) / 8)) {
        ext4_unlock_group(sb, block_group);
        put_bh(bh);
        ext4_error(sb, "Corrupt inode bitmap - block_group = %u, "
               "inode_bitmap = %llu", block_group, bitmap_blk);
        return NULL;
    }
    ext4_unlock_group(sb, block_group);
    set_buffer_verified(bh);
    return bh;
}

/*
 * NOTE! When we get the inode, we're the only people
 * that have access to it, and as such there are no
 * race conditions we have to worry about. The inode
 * is not on the hash-lists, and it cannot be reached
 * through the filesystem because the directory entry
 * has been deleted earlier.
 *
 * HOWEVER: we must make sure that we get no aliases,
 * which means that we have to call "clear_inode()"
 * _before_ we mark the inode not in use in the inode
 * bitmaps. Otherwise a newly created file might use
 * the same inode number (not actually the same pointer
 * though), and then we'd have two inodes sharing the
 * same inode number and space on the harddisk.
 */
void ext4_free_inode(handle_t *handle, struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    int is_directory;
    unsigned long ino;
    struct buffer_head *bitmap_bh = NULL;
    struct buffer_head *bh2;
    ext4_group_t block_group;
    unsigned long bit;
    struct ext4_group_desc *gdp;
    struct ext4_super_block *es;
    struct ext4_sb_info *sbi;
    int fatal = 0, err, count, cleared;

    if (!sb) {
        printk(KERN_ERR "EXT4-fs: %s:%d: inode on "
               "nonexistent device\n", __func__, __LINE__);
        return;
    }
    if (atomic_read(&inode->i_count) > 1) {
        ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: count=%d",
             __func__, __LINE__, inode->i_ino,
             atomic_read(&inode->i_count));
        return;
    }
    if (inode->i_nlink) {
        ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: nlink=%d\n",
             __func__, __LINE__, inode->i_ino, inode->i_nlink);
        return;
    }
    sbi = EXT4_SB(sb);

    ino = inode->i_ino;
    ext4_debug("freeing inode %lu\n", ino);
    trace_ext4_free_inode(inode);

    /*
     * Note: we must free any quota before locking the superblock,
     * as writing the quota to disk may need the lock as well.
     */
    dquot_initialize(inode);
    ext4_xattr_delete_inode(handle, inode);
    dquot_free_inode(inode);
    dquot_drop(inode);

    is_directory = S_ISDIR(inode->i_mode);

    /* Do this BEFORE marking the inode not in use or returning an error */
    ext4_clear_inode(inode);

    es = EXT4_SB(sb)->s_es;
    if (ino < EXT4_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {
        ext4_error(sb, "reserved or nonexistent inode %lu", ino);
        goto error_return;
    }
    block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb);
    bit = (ino - 1) % EXT4_INODES_PER_GROUP(sb);
    bitmap_bh = ext4_read_inode_bitmap(sb, block_group);
    if (!bitmap_bh)
        goto error_return;

    BUFFER_TRACE(bitmap_bh, "get_write_access");
    fatal = ext4_journal_get_write_access(handle, bitmap_bh);
    if (fatal)
        goto error_return;

    fatal = -ESRCH;
    gdp = ext4_get_group_desc(sb, block_group, &bh2);
    if (gdp) {
        BUFFER_TRACE(bh2, "get_write_access");
        fatal = ext4_journal_get_write_access(handle, bh2);
    }
    ext4_lock_group(sb, block_group);
    cleared = ext4_test_and_clear_bit(bit, bitmap_bh->b_data);
    if (fatal || !cleared) {
        ext4_unlock_group(sb, block_group);
        goto out;
    }

    count = ext4_free_inodes_count(sb, gdp) + 1;
    ext4_free_inodes_set(sb, gdp, count);
    if (is_directory) {
        count = ext4_used_dirs_count(sb, gdp) - 1;
        ext4_used_dirs_set(sb, gdp, count);
        percpu_counter_dec(&sbi->s_dirs_counter);
    }
    ext4_inode_bitmap_csum_set(sb, block_group, gdp, bitmap_bh,
                   EXT4_INODES_PER_GROUP(sb) / 8);
    ext4_group_desc_csum_set(sb, block_group, gdp);
    ext4_unlock_group(sb, block_group);

    percpu_counter_inc(&sbi->s_freeinodes_counter);
    if (sbi->s_log_groups_per_flex) {
        ext4_group_t f = ext4_flex_group(sbi, block_group);

        atomic_inc(&sbi->s_flex_groups[f].free_inodes);
        if (is_directory)
            atomic_dec(&sbi->s_flex_groups[f].used_dirs);
    }
    BUFFER_TRACE(bh2, "call ext4_handle_dirty_metadata");
    fatal = ext4_handle_dirty_metadata(handle, NULL, bh2);
out:
    if (cleared) {
        BUFFER_TRACE(bitmap_bh, "call ext4_handle_dirty_metadata");
        err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
        if (!fatal)
            fatal = err;
    } else
        ext4_error(sb, "bit already cleared for inode %lu", ino);

error_return:
    brelse(bitmap_bh);
    ext4_std_error(sb, fatal);
}

struct orlov_stats {
    __u32 free_inodes;
    __u32 free_clusters;
    __u32 used_dirs;
};

/*
 * Helper function for Orlov's allocator; returns critical information
 * for a particular block group or flex_bg.  If flex_size is 1, then g
 * is a block group number; otherwise it is flex_bg number.
 */
static void get_orlov_stats(struct super_block *sb, ext4_group_t g,
                int flex_size, struct orlov_stats *stats)
{
    struct ext4_group_desc *desc;
    struct flex_groups *flex_group = EXT4_SB(sb)->s_flex_groups;

    if (flex_size > 1) {
        stats->free_inodes = atomic_read(&flex_group[g].free_inodes);
        stats->free_clusters = atomic_read(&flex_group[g].free_clusters);
        stats->used_dirs = atomic_read(&flex_group[g].used_dirs);
        return;
    }

    desc = ext4_get_group_desc(sb, g, NULL);
    if (desc) {
        stats->free_inodes = ext4_free_inodes_count(sb, desc);
        stats->free_clusters = ext4_free_group_clusters(sb, desc);
        stats->used_dirs = ext4_used_dirs_count(sb, desc);
    } else {
        stats->free_inodes = 0;
        stats->free_clusters = 0;
        stats->used_dirs = 0;
    }
}

/*
 * Orlov's allocator for directories.
 *
 * We always try to spread first-level directories.
 *
 * If there are blockgroups with both free inodes and free blocks counts
 * not worse than average we return one with smallest directory count.
 * Otherwise we simply return a random group.
 *
 * For the rest rules look so:
 *
 * It's OK to put directory into a group unless
 * it has too many directories already (max_dirs) or
 * it has too few free inodes left (min_inodes) or
 * it has too few free blocks left (min_blocks) or
 * Parent's group is preferred, if it doesn't satisfy these
 * conditions we search cyclically through the rest. If none
 * of the groups look good we just look for a group with more
 * free inodes than average (starting at parent's group).
 */

static int find_group_orlov(struct super_block *sb, struct inode *parent,
                ext4_group_t *group, umode_t mode,
                const struct qstr *qstr)
{
    ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    ext4_group_t real_ngroups = ext4_get_groups_count(sb);
    int inodes_per_group = EXT4_INODES_PER_GROUP(sb);
    unsigned int freei, avefreei, grp_free;
    ext4_fsblk_t freeb, avefreec;
    unsigned int ndirs;
    int max_dirs, min_inodes;
    ext4_grpblk_t min_clusters;
    ext4_group_t i, grp, g, ngroups;
    struct ext4_group_desc *desc;
    struct orlov_stats stats;
    int flex_size = ext4_flex_bg_size(sbi);
    struct dx_hash_info hinfo;

    ngroups = real_ngroups;
    if (flex_size > 1) {
        ngroups = (real_ngroups + flex_size - 1) >>
            sbi->s_log_groups_per_flex;
        parent_group >>= sbi->s_log_groups_per_flex;
    }

    freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
    avefreei = freei / ngroups;
    freeb = EXT4_C2B(sbi,
        percpu_counter_read_positive(&sbi->s_freeclusters_counter));
    avefreec = freeb;
    do_div(avefreec, ngroups);
    ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);

    if (S_ISDIR(mode) &&
        ((parent == sb->s_root->d_inode) ||
         (ext4_test_inode_flag(parent, EXT4_INODE_TOPDIR)))) {
        int best_ndir = inodes_per_group;
        int ret = -1;

        if (qstr) {
            hinfo.hash_version = DX_HASH_HALF_MD4;
            hinfo.seed = sbi->s_hash_seed;
            ext4fs_dirhash(qstr->name, qstr->len, &hinfo);
            grp = hinfo.hash;
        } else
            get_random_bytes(&grp, sizeof(grp));
        parent_group = (unsigned)grp % ngroups;
        for (i = 0; i < ngroups; i++) {
            g = (parent_group + i) % ngroups;
            get_orlov_stats(sb, g, flex_size, &stats);
            if (!stats.free_inodes)
                continue;
            if (stats.used_dirs >= best_ndir)
                continue;
            if (stats.free_inodes < avefreei)
                continue;
            if (stats.free_clusters < avefreec)
                continue;
            grp = g;
            ret = 0;
            best_ndir = stats.used_dirs;
        }
        if (ret)
            goto fallback;
    found_flex_bg:
        if (flex_size == 1) {
            *group = grp;
            return 0;
        }

        /*
         * We pack inodes at the beginning of the flexgroup's
         * inode tables.  Block allocation decisions will do
         * something similar, although regular files will
         * start at 2nd block group of the flexgroup.  See
         * ext4_ext_find_goal() and ext4_find_near().
         */
        grp *= flex_size;
        for (i = 0; i < flex_size; i++) {
            if (grp+i >= real_ngroups)
                break;
            desc = ext4_get_group_desc(sb, grp+i, NULL);
            if (desc && ext4_free_inodes_count(sb, desc)) {
                *group = grp+i;
                return 0;
            }
        }
        goto fallback;
    }

    max_dirs = ndirs / ngroups + inodes_per_group / 16;
    min_inodes = avefreei - inodes_per_group*flex_size / 4;
    if (min_inodes < 1)
        min_inodes = 1;
    min_clusters = avefreec - EXT4_CLUSTERS_PER_GROUP(sb)*flex_size / 4;

    /*
     * Start looking in the flex group where we last allocated an
     * inode for this parent directory
     */
    if (EXT4_I(parent)->i_last_alloc_group != ~0) {
        parent_group = EXT4_I(parent)->i_last_alloc_group;
        if (flex_size > 1)
            parent_group >>= sbi->s_log_groups_per_flex;
    }

    for (i = 0; i < ngroups; i++) {
        grp = (parent_group + i) % ngroups;
        get_orlov_stats(sb, grp, flex_size, &stats);
        if (stats.used_dirs >= max_dirs)
            continue;
        if (stats.free_inodes < min_inodes)
            continue;
        if (stats.free_clusters < min_clusters)
            continue;
        goto found_flex_bg;
    }

fallback:
    ngroups = real_ngroups;
    avefreei = freei / ngroups;
fallback_retry:
    parent_group = EXT4_I(parent)->i_block_group;
    for (i = 0; i < ngroups; i++) {
        grp = (parent_group + i) % ngroups;
        desc = ext4_get_group_desc(sb, grp, NULL);
        if (desc) {
            grp_free = ext4_free_inodes_count(sb, desc);
            if (grp_free && grp_free >= avefreei) {
                *group = grp;
                return 0;
            }
        }
    }

    if (avefreei) {
        /*
         * The free-inodes counter is approximate, and for really small
         * filesystems the above test can fail to find any blockgroups
         */
        avefreei = 0;
        goto fallback_retry;
    }

    return -1;
}

static int find_group_other(struct super_block *sb, struct inode *parent,
                ext4_group_t *group, umode_t mode)
{
    ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
    ext4_group_t i, last, ngroups = ext4_get_groups_count(sb);
    struct ext4_group_desc *desc;
    int flex_size = ext4_flex_bg_size(EXT4_SB(sb));

    /*
     * Try to place the inode is the same flex group as its
     * parent.  If we can't find space, use the Orlov algorithm to
     * find another flex group, and store that information in the
     * parent directory's inode information so that use that flex
     * group for future allocations.
     */
    if (flex_size > 1) {
        int retry = 0;

    try_again:
        parent_group &= ~(flex_size-1);
        last = parent_group + flex_size;
        if (last > ngroups)
            last = ngroups;
        for  (i = parent_group; i < last; i++) {
            desc = ext4_get_group_desc(sb, i, NULL);
            if (desc && ext4_free_inodes_count(sb, desc)) {
                *group = i;
                return 0;
            }
        }
        if (!retry && EXT4_I(parent)->i_last_alloc_group != ~0) {
            retry = 1;
            parent_group = EXT4_I(parent)->i_last_alloc_group;
            goto try_again;
        }
        /*
         * If this didn't work, use the Orlov search algorithm
         * to find a new flex group; we pass in the mode to
         * avoid the topdir algorithms.
         */
        *group = parent_group + flex_size;
        if (*group > ngroups)
            *group = 0;
        return find_group_orlov(sb, parent, group, mode, NULL);
    }

    /*
     * Try to place the inode in its parent directory
     */
    *group = parent_group;
    desc = ext4_get_group_desc(sb, *group, NULL);
    if (desc && ext4_free_inodes_count(sb, desc) &&
        ext4_free_group_clusters(sb, desc))
        return 0;

    /*
     * We're going to place this inode in a different blockgroup from its
     * parent.  We want to cause files in a common directory to all land in
     * the same blockgroup.  But we want files which are in a different
     * directory which shares a blockgroup with our parent to land in a
     * different blockgroup.
     *
     * So add our directory's i_ino into the starting point for the hash.
     */
    *group = (*group + parent->i_ino) % ngroups;

    /*
     * Use a quadratic hash to find a group with a free inode and some free
     * blocks.
     */
    for (i = 1; i < ngroups; i <<= 1) {
        *group += i;
        if (*group >= ngroups)
            *group -= ngroups;
        desc = ext4_get_group_desc(sb, *group, NULL);
        if (desc && ext4_free_inodes_count(sb, desc) &&
            ext4_free_group_clusters(sb, desc))
            return 0;
    }

    /*
     * That failed: try linear search for a free inode, even if that group
     * has no free blocks.
     */
    *group = parent_group;
    for (i = 0; i < ngroups; i++) {
        if (++*group >= ngroups)
            *group = 0;
        desc = ext4_get_group_desc(sb, *group, NULL);
        if (desc && ext4_free_inodes_count(sb, desc))
            return 0;
    }

    return -1;
}

/*
 * There are two policies for allocating an inode.  If the new inode is
 * a directory, then a forward search is made for a block group with both
 * free space and a low directory-to-inode ratio; if that fails, then of
 * the groups with above-average free space, that group with the fewest
 * directories already is chosen.
 *
 * For other inodes, search forward from the parent directory's block
 * group to find a free inode.
 */
struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
                 const struct qstr *qstr, __u32 goal, uid_t *owner)
{
    struct super_block *sb;
    struct buffer_head *inode_bitmap_bh = NULL;
    struct buffer_head *group_desc_bh;
    ext4_group_t ngroups, group = 0;
    unsigned long ino = 0;
    struct inode *inode;
    struct ext4_group_desc *gdp = NULL;
    struct ext4_inode_info *ei;
    struct ext4_sb_info *sbi;
    int ret2, err = 0;
    struct inode *ret;
    ext4_group_t i;
    ext4_group_t flex_group;

    /* Cannot create files in a deleted directory */
    if (!dir || !dir->i_nlink)
        return ERR_PTR(-EPERM);

    sb = dir->i_sb;
    ngroups = ext4_get_groups_count(sb);
    trace_ext4_request_inode(dir, mode);
    inode = new_inode(sb);
    if (!inode)
        return ERR_PTR(-ENOMEM);
    ei = EXT4_I(inode);
    sbi = EXT4_SB(sb);

    if (!goal)
        goal = sbi->s_inode_goal;

    if (goal && goal <= le32_to_cpu(sbi->s_es->s_inodes_count)) {
        group = (goal - 1) / EXT4_INODES_PER_GROUP(sb);
        ino = (goal - 1) % EXT4_INODES_PER_GROUP(sb);
        ret2 = 0;
        goto got_group;
    }

    if (S_ISDIR(mode))
        ret2 = find_group_orlov(sb, dir, &group, mode, qstr);
    else
        ret2 = find_group_other(sb, dir, &group, mode);

got_group:
    EXT4_I(dir)->i_last_alloc_group = group;
    err = -ENOSPC;
    if (ret2 == -1)
        goto out;

    /*
     * Normally we will only go through one pass of this loop,
     * unless we get unlucky and it turns out the group we selected
     * had its last inode grabbed by someone else.
     */
    for (i = 0; i < ngroups; i++, ino = 0) {
        err = -EIO;

        gdp = ext4_get_group_desc(sb, group, &group_desc_bh);
        if (!gdp)
            goto fail;

        /*
         * Check free inodes count before loading bitmap.
         */
        if (ext4_free_inodes_count(sb, gdp) == 0) {
            if (++group == ngroups)
                group = 0;
            continue;
        }

        brelse(inode_bitmap_bh);
        inode_bitmap_bh = ext4_read_inode_bitmap(sb, group);
        if (!inode_bitmap_bh)
            goto fail;

repeat_in_this_group:
        ino = ext4_find_next_zero_bit((unsigned long *)
                          inode_bitmap_bh->b_data,
                          EXT4_INODES_PER_GROUP(sb), ino);
        if (ino >= EXT4_INODES_PER_GROUP(sb)) {
            if (++group == ngroups)
                group = 0;
            continue;
        }
        if (group == 0 && (ino+1) < EXT4_FIRST_INO(sb)) {
            ext4_error(sb, "reserved inode found cleared - "
                   "inode=%lu", ino + 1);
            continue;
        }
        BUFFER_TRACE(inode_bitmap_bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, inode_bitmap_bh);
        if (err)
            goto fail;
        ext4_lock_group(sb, group);
        ret2 = ext4_test_and_set_bit(ino, inode_bitmap_bh->b_data);
        ext4_unlock_group(sb, group);
        ino++;      /* the inode bitmap is zero-based */
        if (!ret2)
            goto got; /* we grabbed the inode! */
        if (ino < EXT4_INODES_PER_GROUP(sb))
            goto repeat_in_this_group;
    }
    err = -ENOSPC;
    goto out;

got:
    BUFFER_TRACE(inode_bitmap_bh, "call ext4_handle_dirty_metadata");
    err = ext4_handle_dirty_metadata(handle, NULL, inode_bitmap_bh);
    if (err)
        goto fail;

    /* We may have to initialize the block bitmap if it isn't already */
    if (ext4_has_group_desc_csum(sb) &&
        gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
        struct buffer_head *block_bitmap_bh;

        block_bitmap_bh = ext4_read_block_bitmap(sb, group);
        BUFFER_TRACE(block_bitmap_bh, "get block bitmap access");
        err = ext4_journal_get_write_access(handle, block_bitmap_bh);
        if (err) {
            brelse(block_bitmap_bh);
            goto fail;
        }

        BUFFER_TRACE(block_bitmap_bh, "dirty block bitmap");
        err = ext4_handle_dirty_metadata(handle, NULL, block_bitmap_bh);
        brelse(block_bitmap_bh);

        /* recheck and clear flag under lock if we still need to */
        ext4_lock_group(sb, group);
        if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
            gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
            ext4_free_group_clusters_set(sb, gdp,
                ext4_free_clusters_after_init(sb, group, gdp));
            ext4_block_bitmap_csum_set(sb, group, gdp,
                           block_bitmap_bh);
            ext4_group_desc_csum_set(sb, group, gdp);
        }
        ext4_unlock_group(sb, group);

        if (err)
            goto fail;
    }

    BUFFER_TRACE(group_desc_bh, "get_write_access");
    err = ext4_journal_get_write_access(handle, group_desc_bh);
    if (err)
        goto fail;

    /* Update the relevant bg descriptor fields */
    if (ext4_has_group_desc_csum(sb)) {
        int free;
        struct ext4_group_info *grp = ext4_get_group_info(sb, group);

        down_read(&grp->alloc_sem); /* protect vs itable lazyinit */
        ext4_lock_group(sb, group); /* while we modify the bg desc */
        free = EXT4_INODES_PER_GROUP(sb) -
            ext4_itable_unused_count(sb, gdp);
        if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
            gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
            free = 0;
        }
        /*
         * Check the relative inode number against the last used
         * relative inode number in this group. if it is greater
         * we need to update the bg_itable_unused count
         */
        if (ino > free)
            ext4_itable_unused_set(sb, gdp,
                    (EXT4_INODES_PER_GROUP(sb) - ino));
        up_read(&grp->alloc_sem);
    } else {
        ext4_lock_group(sb, group);
    }

    ext4_free_inodes_set(sb, gdp, ext4_free_inodes_count(sb, gdp) - 1);
    if (S_ISDIR(mode)) {
        ext4_used_dirs_set(sb, gdp, ext4_used_dirs_count(sb, gdp) + 1);
        if (sbi->s_log_groups_per_flex) {
            ext4_group_t f = ext4_flex_group(sbi, group);

            atomic_inc(&sbi->s_flex_groups[f].used_dirs);
        }
    }
    if (ext4_has_group_desc_csum(sb)) {
        ext4_inode_bitmap_csum_set(sb, group, gdp, inode_bitmap_bh,
                       EXT4_INODES_PER_GROUP(sb) / 8);
        ext4_group_desc_csum_set(sb, group, gdp);
    }
    ext4_unlock_group(sb, group);

    BUFFER_TRACE(group_desc_bh, "call ext4_handle_dirty_metadata");
    err = ext4_handle_dirty_metadata(handle, NULL, group_desc_bh);
    if (err)
        goto fail;

    percpu_counter_dec(&sbi->s_freeinodes_counter);
    if (S_ISDIR(mode))
        percpu_counter_inc(&sbi->s_dirs_counter);

    if (sbi->s_log_groups_per_flex) {
        flex_group = ext4_flex_group(sbi, group);
        atomic_dec(&sbi->s_flex_groups[flex_group].free_inodes);
    }
    if (owner) {
        inode->i_mode = mode;
        i_uid_write(inode, owner[0]);
        i_gid_write(inode, owner[1]);
    } else if (test_opt(sb, GRPID)) {
        inode->i_mode = mode;
        inode->i_uid = current_fsuid();
        inode->i_gid = dir->i_gid;
    } else
        inode_init_owner(inode, dir, mode);

    inode->i_ino = ino + group * EXT4_INODES_PER_GROUP(sb);
    /* This is the optimal IO size (for stat), not the fs block size */
    inode->i_blocks = 0;
    inode->i_mtime = inode->i_atime = inode->i_ctime = ei->i_crtime =
                               ext4_current_time(inode);

    memset(ei->i_data, 0, sizeof(ei->i_data));
    ei->i_dir_start_lookup = 0;
    ei->i_disksize = 0;

    /* Don't inherit extent flag from directory, amongst others. */
    ei->i_flags =
        ext4_mask_flags(mode, EXT4_I(dir)->i_flags & EXT4_FL_INHERITED);
    ei->i_file_acl = 0;
    ei->i_dtime = 0;
    ei->i_block_group = group;
    ei->i_last_alloc_group = ~0;

    ext4_set_inode_flags(inode);
    if (IS_DIRSYNC(inode))
        ext4_handle_sync(handle);
    if (insert_inode_locked(inode) < 0) {
        /*
         * Likely a bitmap corruption causing inode to be allocated
         * twice.
         */
        err = -EIO;
        goto fail;
    }
    spin_lock(&sbi->s_next_gen_lock);
    inode->i_generation = sbi->s_next_generation++;
    spin_unlock(&sbi->s_next_gen_lock);

    /* Precompute checksum seed for inode metadata */
    if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
            EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
        __u32 csum;
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        __le32 inum = cpu_to_le32(inode->i_ino);
        __le32 gen = cpu_to_le32(inode->i_generation);
        csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum,
                   sizeof(inum));
        ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen,
                          sizeof(gen));
    }

    ext4_clear_state_flags(ei); /* Only relevant on 32-bit archs */
    ext4_set_inode_state(inode, EXT4_STATE_NEW);

    ei->i_extra_isize = EXT4_SB(sb)->s_want_extra_isize;

    ret = inode;
    dquot_initialize(inode);
    err = dquot_alloc_inode(inode);
    if (err)
        goto fail_drop;

    err = ext4_init_acl(handle, inode, dir);
    if (err)
        goto fail_free_drop;

    err = ext4_init_security(handle, inode, dir, qstr);
    if (err)
        goto fail_free_drop;

    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS)) {
        /* set extent flag only for directory, file and normal symlink*/
        if (S_ISDIR(mode) || S_ISREG(mode) || S_ISLNK(mode)) {
            ext4_set_inode_flag(inode, EXT4_INODE_EXTENTS);
            ext4_ext_tree_init(handle, inode);
        }
    }

    if (ext4_handle_valid(handle)) {
        ei->i_sync_tid = handle->h_transaction->t_tid;
        ei->i_datasync_tid = handle->h_transaction->t_tid;
    }

    err = ext4_mark_inode_dirty(handle, inode);
    if (err) {
        ext4_std_error(sb, err);
        goto fail_free_drop;
    }

    ext4_debug("allocating inode %lu\n", inode->i_ino);
    trace_ext4_allocate_inode(inode, dir, mode);
    goto really_out;
fail:
    ext4_std_error(sb, err);
out:
    iput(inode);
    ret = ERR_PTR(err);
really_out:
    brelse(inode_bitmap_bh);
    return ret;

fail_free_drop:
    dquot_free_inode(inode);

fail_drop:
    dquot_drop(inode);
    inode->i_flags |= S_NOQUOTA;
    clear_nlink(inode);
    unlock_new_inode(inode);
    iput(inode);
    brelse(inode_bitmap_bh);
    return ERR_PTR(err);
}

/* Verify that we are loading a valid orphan from disk */
struct inode *ext4_orphan_get(struct super_block *sb, unsigned long ino)
{
    unsigned long max_ino = le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count);
    ext4_group_t block_group;
    int bit;
    struct buffer_head *bitmap_bh;
    struct inode *inode = NULL;
    long err = -EIO;

    /* Error cases - e2fsck has already cleaned up for us */
    if (ino > max_ino) {
        ext4_warning(sb, "bad orphan ino %lu!  e2fsck was run?", ino);
        goto error;
    }

    block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb);
    bit = (ino - 1) % EXT4_INODES_PER_GROUP(sb);
    bitmap_bh = ext4_read_inode_bitmap(sb, block_group);
    if (!bitmap_bh) {
        ext4_warning(sb, "inode bitmap error for orphan %lu", ino);
        goto error;
    }

    /* Having the inode bit set should be a 100% indicator that this
     * is a valid orphan (no e2fsck run on fs).  Orphans also include
     * inodes that were being truncated, so we can't check i_nlink==0.
     */
    if (!ext4_test_bit(bit, bitmap_bh->b_data))
        goto bad_orphan;

    inode = ext4_iget(sb, ino);
    if (IS_ERR(inode))
        goto iget_failed;

    /*
     * If the orphans has i_nlinks > 0 then it should be able to be
     * truncated, otherwise it won't be removed from the orphan list
     * during processing and an infinite loop will result.
     */
    if (inode->i_nlink && !ext4_can_truncate(inode))
        goto bad_orphan;

    if (NEXT_ORPHAN(inode) > max_ino)
        goto bad_orphan;
    brelse(bitmap_bh);
    return inode;

iget_failed:
    err = PTR_ERR(inode);
    inode = NULL;
bad_orphan:
    ext4_warning(sb, "bad orphan inode %lu!  e2fsck was run?", ino);
    printk(KERN_NOTICE "ext4_test_bit(bit=%d, block=%llu) = %d\n",
           bit, (unsigned long long)bitmap_bh->b_blocknr,
           ext4_test_bit(bit, bitmap_bh->b_data));
    printk(KERN_NOTICE "inode=%p\n", inode);
    if (inode) {
        printk(KERN_NOTICE "is_bad_inode(inode)=%d\n",
               is_bad_inode(inode));
        printk(KERN_NOTICE "NEXT_ORPHAN(inode)=%u\n",
               NEXT_ORPHAN(inode));
        printk(KERN_NOTICE "max_ino=%lu\n", max_ino);
        printk(KERN_NOTICE "i_nlink=%u\n", inode->i_nlink);
        /* Avoid freeing blocks if we got a bad deleted inode */
        if (inode->i_nlink == 0)
            inode->i_blocks = 0;
        iput(inode);
    }
    brelse(bitmap_bh);
error:
    return ERR_PTR(err);
}

unsigned long ext4_count_free_inodes(struct super_block *sb)
{
    unsigned long desc_count;
    struct ext4_group_desc *gdp;
    ext4_group_t i, ngroups = ext4_get_groups_count(sb);
#ifdef EXT4FS_DEBUG
    struct ext4_super_block *es;
    unsigned long bitmap_count, x;
    struct buffer_head *bitmap_bh = NULL;

    es = EXT4_SB(sb)->s_es;
    desc_count = 0;
    bitmap_count = 0;
    gdp = NULL;
    for (i = 0; i < ngroups; i++) {
        gdp = ext4_get_group_desc(sb, i, NULL);
        if (!gdp)
            continue;
        desc_count += ext4_free_inodes_count(sb, gdp);
        brelse(bitmap_bh);
        bitmap_bh = ext4_read_inode_bitmap(sb, i);
        if (!bitmap_bh)
            continue;

        x = ext4_count_free(bitmap_bh->b_data,
                    EXT4_INODES_PER_GROUP(sb) / 8);
        printk(KERN_DEBUG "group %lu: stored = %d, counted = %lu\n",
            (unsigned long) i, ext4_free_inodes_count(sb, gdp), x);
        bitmap_count += x;
    }
    brelse(bitmap_bh);
    printk(KERN_DEBUG "ext4_count_free_inodes: "
           "stored = %u, computed = %lu, %lu\n",
           le32_to_cpu(es->s_free_inodes_count), desc_count, bitmap_count);
    return desc_count;
#else
    desc_count = 0;
    for (i = 0; i < ngroups; i++) {
        gdp = ext4_get_group_desc(sb, i, NULL);
        if (!gdp)
            continue;
        desc_count += ext4_free_inodes_count(sb, gdp);
        cond_resched();
    }
    return desc_count;
#endif
}

/* Called at mount-time, super-block is locked */
unsigned long ext4_count_dirs(struct super_block * sb)
{
    unsigned long count = 0;
    ext4_group_t i, ngroups = ext4_get_groups_count(sb);

    for (i = 0; i < ngroups; i++) {
        struct ext4_group_desc *gdp = ext4_get_group_desc(sb, i, NULL);
        if (!gdp)
            continue;
        count += ext4_used_dirs_count(sb, gdp);
    }
    return count;
}

/*
 * Zeroes not yet zeroed inode table - just write zeroes through the whole
 * inode table. Must be called without any spinlock held. The only place
 * where it is called from on active part of filesystem is ext4lazyinit
 * thread, so we do not need any special locks, however we have to prevent
 * inode allocation from the current group, so we take alloc_sem lock, to
 * block ext4_new_inode() until we are finished.
 */
int ext4_init_inode_table(struct super_block *sb, ext4_group_t group,
                 int barrier)
{
    struct ext4_group_info *grp = ext4_get_group_info(sb, group);
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    struct ext4_group_desc *gdp = NULL;
    struct buffer_head *group_desc_bh;
    handle_t *handle;
    ext4_fsblk_t blk;
    int num, ret = 0, used_blks = 0;

    /* This should not happen, but just to be sure check this */
    if (sb->s_flags & MS_RDONLY) {
        ret = 1;
        goto out;
    }

    gdp = ext4_get_group_desc(sb, group, &group_desc_bh);
    if (!gdp)
        goto out;

    /*
     * We do not need to lock this, because we are the only one
     * handling this flag.
     */
    if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_ZEROED))
        goto out;

    handle = ext4_journal_start_sb(sb, 1);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        goto out;
    }

    down_write(&grp->alloc_sem);
    /*
     * If inode bitmap was already initialized there may be some
     * used inodes so we need to skip blocks with used inodes in
     * inode table.
     */
    if (!(gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)))
        used_blks = DIV_ROUND_UP((EXT4_INODES_PER_GROUP(sb) -
                ext4_itable_unused_count(sb, gdp)),
                sbi->s_inodes_per_block);

    if ((used_blks < 0) || (used_blks > sbi->s_itb_per_group)) {
        ext4_error(sb, "Something is wrong with group %u: "
               "used itable blocks: %d; "
               "itable unused count: %u",
               group, used_blks,
               ext4_itable_unused_count(sb, gdp));
        ret = 1;
        goto err_out;
    }

    blk = ext4_inode_table(sb, gdp) + used_blks;
    num = sbi->s_itb_per_group - used_blks;

    BUFFER_TRACE(group_desc_bh, "get_write_access");
    ret = ext4_journal_get_write_access(handle,
                        group_desc_bh);
    if (ret)
        goto err_out;

    /*
     * Skip zeroout if the inode table is full. But we set the ZEROED
     * flag anyway, because obviously, when it is full it does not need
     * further zeroing.
     */
    if (unlikely(num == 0))
        goto skip_zeroout;

    ext4_debug("going to zero out inode table in group %d\n",
           group);
    ret = sb_issue_zeroout(sb, blk, num, GFP_NOFS);
    if (ret < 0)
        goto err_out;
    if (barrier)
        blkdev_issue_flush(sb->s_bdev, GFP_NOFS, NULL);

skip_zeroout:
    ext4_lock_group(sb, group);
    gdp->bg_flags |= cpu_to_le16(EXT4_BG_INODE_ZEROED);
    ext4_group_desc_csum_set(sb, group, gdp);
    ext4_unlock_group(sb, group);

    BUFFER_TRACE(group_desc_bh,
             "call ext4_handle_dirty_metadata");
    ret = ext4_handle_dirty_metadata(handle, NULL,
                     group_desc_bh);

err_out:
    up_write(&grp->alloc_sem);
    ext4_journal_stop(handle);
out:
    return ret;
}