namei.c

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/*
 *  linux/fs/ext4/namei.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/namei.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 *  Directory entry file type support and forward compatibility hooks
 *  for B-tree directories by Theodore Ts'o ([email protected]), 1998
 *  Hash Tree Directory indexing (c)
 *  Daniel Phillips, 2001
 *  Hash Tree Directory indexing porting
 *  Christopher Li, 2002
 *  Hash Tree Directory indexing cleanup
 *  Theodore Ts'o, 2002
 */

#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/jbd2.h>
#include <linux/time.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/bio.h>
#include "ext4.h"
#include "ext4_jbd2.h"

#include "xattr.h"
#include "acl.h"

#include <trace/events/ext4.h>
/*
 * define how far ahead to read directories while searching them.
 */
#define NAMEI_RA_CHUNKS  2
#define NAMEI_RA_BLOCKS  4
#define NAMEI_RA_SIZE        (NAMEI_RA_CHUNKS * NAMEI_RA_BLOCKS)
#define NAMEI_RA_INDEX(c,b)  (((c) * NAMEI_RA_BLOCKS) + (b))

static struct buffer_head *ext4_append(handle_t *handle,
                    struct inode *inode,
                    ext4_lblk_t *block, int *err)
{
    struct buffer_head *bh;

    if (unlikely(EXT4_SB(inode->i_sb)->s_max_dir_size_kb &&
             ((inode->i_size >> 10) >=
              EXT4_SB(inode->i_sb)->s_max_dir_size_kb))) {
        *err = -ENOSPC;
        return NULL;
    }

    *block = inode->i_size >> inode->i_sb->s_blocksize_bits;

    bh = ext4_bread(handle, inode, *block, 1, err);
    if (bh) {
        inode->i_size += inode->i_sb->s_blocksize;
        EXT4_I(inode)->i_disksize = inode->i_size;
        *err = ext4_journal_get_write_access(handle, bh);
        if (*err) {
            brelse(bh);
            bh = NULL;
        }
    }
    if (!bh && !(*err)) {
        *err = -EIO;
        ext4_error(inode->i_sb,
               "Directory hole detected on inode %lu\n",
               inode->i_ino);
    }
    return bh;
}

#ifndef assert
#define assert(test) J_ASSERT(test)
#endif

#ifdef DX_DEBUG
#define dxtrace(command) command
#else
#define dxtrace(command)
#endif

struct fake_dirent
{
    __le32 inode;
    __le16 rec_len;
    u8 name_len;
    u8 file_type;
};

struct dx_countlimit
{
    __le16 limit;
    __le16 count;
};

struct dx_entry
{
    __le32 hash;
    __le32 block;
};

/*
 * dx_root_info is laid out so that if it should somehow get overlaid by a
 * dirent the two low bits of the hash version will be zero.  Therefore, the
 * hash version mod 4 should never be 0.  Sincerely, the paranoia department.
 */

struct dx_root
{
    struct fake_dirent dot;
    char dot_name[4];
    struct fake_dirent dotdot;
    char dotdot_name[4];
    struct dx_root_info
    {
        __le32 reserved_zero;
        u8 hash_version;
        u8 info_length; /* 8 */
        u8 indirect_levels;
        u8 unused_flags;
    }
    info;
    struct dx_entry entries[0];
};

struct dx_node
{
    struct fake_dirent fake;
    struct dx_entry entries[0];
};


struct dx_frame
{
    struct buffer_head *bh;
    struct dx_entry *entries;
    struct dx_entry *at;
};

struct dx_map_entry
{
    u32 hash;
    u16 offs;
    u16 size;
};

/*
 * This goes at the end of each htree block.
 */
struct dx_tail {
    u32 dt_reserved;
    __le32 dt_checksum; /* crc32c(uuid+inum+dirblock) */
};

static inline ext4_lblk_t dx_get_block(struct dx_entry *entry);
static void dx_set_block(struct dx_entry *entry, ext4_lblk_t value);
static inline unsigned dx_get_hash(struct dx_entry *entry);
static void dx_set_hash(struct dx_entry *entry, unsigned value);
static unsigned dx_get_count(struct dx_entry *entries);
static unsigned dx_get_limit(struct dx_entry *entries);
static void dx_set_count(struct dx_entry *entries, unsigned value);
static void dx_set_limit(struct dx_entry *entries, unsigned value);
static unsigned dx_root_limit(struct inode *dir, unsigned infosize);
static unsigned dx_node_limit(struct inode *dir);
static struct dx_frame *dx_probe(const struct qstr *d_name,
                 struct inode *dir,
                 struct dx_hash_info *hinfo,
                 struct dx_frame *frame,
                 int *err);
static void dx_release(struct dx_frame *frames);
static int dx_make_map(struct ext4_dir_entry_2 *de, unsigned blocksize,
               struct dx_hash_info *hinfo, struct dx_map_entry map[]);
static void dx_sort_map(struct dx_map_entry *map, unsigned count);
static struct ext4_dir_entry_2 *dx_move_dirents(char *from, char *to,
        struct dx_map_entry *offsets, int count, unsigned blocksize);
static struct ext4_dir_entry_2* dx_pack_dirents(char *base, unsigned blocksize);
static void dx_insert_block(struct dx_frame *frame,
                    u32 hash, ext4_lblk_t block);
static int ext4_htree_next_block(struct inode *dir, __u32 hash,
                 struct dx_frame *frame,
                 struct dx_frame *frames,
                 __u32 *start_hash);
static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
        const struct qstr *d_name,
        struct ext4_dir_entry_2 **res_dir,
        int *err);
static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
                 struct inode *inode);

/* checksumming functions */
#define EXT4_DIRENT_TAIL(block, blocksize) \
    ((struct ext4_dir_entry_tail *)(((void *)(block)) + \
                    ((blocksize) - \
                     sizeof(struct ext4_dir_entry_tail))))

static void initialize_dirent_tail(struct ext4_dir_entry_tail *t,
                   unsigned int blocksize)
{
    memset(t, 0, sizeof(struct ext4_dir_entry_tail));
    t->det_rec_len = ext4_rec_len_to_disk(
            sizeof(struct ext4_dir_entry_tail), blocksize);
    t->det_reserved_ft = EXT4_FT_DIR_CSUM;
}

/* Walk through a dirent block to find a checksum "dirent" at the tail */
static struct ext4_dir_entry_tail *get_dirent_tail(struct inode *inode,
                           struct ext4_dir_entry *de)
{
    struct ext4_dir_entry_tail *t;

#ifdef PARANOID
    struct ext4_dir_entry *d, *top;

    d = de;
    top = (struct ext4_dir_entry *)(((void *)de) +
        (EXT4_BLOCK_SIZE(inode->i_sb) -
        sizeof(struct ext4_dir_entry_tail)));
    while (d < top && d->rec_len)
        d = (struct ext4_dir_entry *)(((void *)d) +
            le16_to_cpu(d->rec_len));

    if (d != top)
        return NULL;

    t = (struct ext4_dir_entry_tail *)d;
#else
    t = EXT4_DIRENT_TAIL(de, EXT4_BLOCK_SIZE(inode->i_sb));
#endif

    if (t->det_reserved_zero1 ||
        le16_to_cpu(t->det_rec_len) != sizeof(struct ext4_dir_entry_tail) ||
        t->det_reserved_zero2 ||
        t->det_reserved_ft != EXT4_FT_DIR_CSUM)
        return NULL;

    return t;
}

static __le32 ext4_dirent_csum(struct inode *inode,
                   struct ext4_dir_entry *dirent, int size)
{
    struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
    struct ext4_inode_info *ei = EXT4_I(inode);
    __u32 csum;

    csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
    return cpu_to_le32(csum);
}

int ext4_dirent_csum_verify(struct inode *inode, struct ext4_dir_entry *dirent)
{
    struct ext4_dir_entry_tail *t;

    if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return 1;

    t = get_dirent_tail(inode, dirent);
    if (!t) {
        EXT4_ERROR_INODE(inode, "metadata_csum set but no space in dir "
                 "leaf for checksum.  Please run e2fsck -D.");
        return 0;
    }

    if (t->det_checksum != ext4_dirent_csum(inode, dirent,
                        (void *)t - (void *)dirent))
        return 0;

    return 1;
}

static void ext4_dirent_csum_set(struct inode *inode,
                 struct ext4_dir_entry *dirent)
{
    struct ext4_dir_entry_tail *t;

    if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return;

    t = get_dirent_tail(inode, dirent);
    if (!t) {
        EXT4_ERROR_INODE(inode, "metadata_csum set but no space in dir "
                 "leaf for checksum.  Please run e2fsck -D.");
        return;
    }

    t->det_checksum = ext4_dirent_csum(inode, dirent,
                       (void *)t - (void *)dirent);
}

static inline int ext4_handle_dirty_dirent_node(handle_t *handle,
                        struct inode *inode,
                        struct buffer_head *bh)
{
    ext4_dirent_csum_set(inode, (struct ext4_dir_entry *)bh->b_data);
    return ext4_handle_dirty_metadata(handle, inode, bh);
}

static struct dx_countlimit *get_dx_countlimit(struct inode *inode,
                           struct ext4_dir_entry *dirent,
                           int *offset)
{
    struct ext4_dir_entry *dp;
    struct dx_root_info *root;
    int count_offset;

    if (le16_to_cpu(dirent->rec_len) == EXT4_BLOCK_SIZE(inode->i_sb))
        count_offset = 8;
    else if (le16_to_cpu(dirent->rec_len) == 12) {
        dp = (struct ext4_dir_entry *)(((void *)dirent) + 12);
        if (le16_to_cpu(dp->rec_len) !=
            EXT4_BLOCK_SIZE(inode->i_sb) - 12)
            return NULL;
        root = (struct dx_root_info *)(((void *)dp + 12));
        if (root->reserved_zero ||
            root->info_length != sizeof(struct dx_root_info))
            return NULL;
        count_offset = 32;
    } else
        return NULL;

    if (offset)
        *offset = count_offset;
    return (struct dx_countlimit *)(((void *)dirent) + count_offset);
}

static __le32 ext4_dx_csum(struct inode *inode, struct ext4_dir_entry *dirent,
               int count_offset, int count, struct dx_tail *t)
{
    struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
    struct ext4_inode_info *ei = EXT4_I(inode);
    __u32 csum, old_csum;
    int size;

    size = count_offset + (count * sizeof(struct dx_entry));
    old_csum = t->dt_checksum;
    t->dt_checksum = 0;
    csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
    csum = ext4_chksum(sbi, csum, (__u8 *)t, sizeof(struct dx_tail));
    t->dt_checksum = old_csum;

    return cpu_to_le32(csum);
}

static int ext4_dx_csum_verify(struct inode *inode,
                   struct ext4_dir_entry *dirent)
{
    struct dx_countlimit *c;
    struct dx_tail *t;
    int count_offset, limit, count;

    if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return 1;

    c = get_dx_countlimit(inode, dirent, &count_offset);
    if (!c) {
        EXT4_ERROR_INODE(inode, "dir seems corrupt?  Run e2fsck -D.");
        return 1;
    }
    limit = le16_to_cpu(c->limit);
    count = le16_to_cpu(c->count);
    if (count_offset + (limit * sizeof(struct dx_entry)) >
        EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
        EXT4_ERROR_INODE(inode, "metadata_csum set but no space for "
                 "tree checksum found.  Run e2fsck -D.");
        return 1;
    }
    t = (struct dx_tail *)(((struct dx_entry *)c) + limit);

    if (t->dt_checksum != ext4_dx_csum(inode, dirent, count_offset,
                        count, t))
        return 0;
    return 1;
}

static void ext4_dx_csum_set(struct inode *inode, struct ext4_dir_entry *dirent)
{
    struct dx_countlimit *c;
    struct dx_tail *t;
    int count_offset, limit, count;

    if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                    EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        return;

    c = get_dx_countlimit(inode, dirent, &count_offset);
    if (!c) {
        EXT4_ERROR_INODE(inode, "dir seems corrupt?  Run e2fsck -D.");
        return;
    }
    limit = le16_to_cpu(c->limit);
    count = le16_to_cpu(c->count);
    if (count_offset + (limit * sizeof(struct dx_entry)) >
        EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
        EXT4_ERROR_INODE(inode, "metadata_csum set but no space for "
                 "tree checksum.  Run e2fsck -D.");
        return;
    }
    t = (struct dx_tail *)(((struct dx_entry *)c) + limit);

    t->dt_checksum = ext4_dx_csum(inode, dirent, count_offset, count, t);
}

static inline int ext4_handle_dirty_dx_node(handle_t *handle,
                        struct inode *inode,
                        struct buffer_head *bh)
{
    ext4_dx_csum_set(inode, (struct ext4_dir_entry *)bh->b_data);
    return ext4_handle_dirty_metadata(handle, inode, bh);
}

/*
 * p is at least 6 bytes before the end of page
 */
static inline struct ext4_dir_entry_2 *
ext4_next_entry(struct ext4_dir_entry_2 *p, unsigned long blocksize)
{
    return (struct ext4_dir_entry_2 *)((char *)p +
        ext4_rec_len_from_disk(p->rec_len, blocksize));
}

/*
 * Future: use high four bits of block for coalesce-on-delete flags
 * Mask them off for now.
 */

static inline ext4_lblk_t dx_get_block(struct dx_entry *entry)
{
    return le32_to_cpu(entry->block) & 0x00ffffff;
}

static inline void dx_set_block(struct dx_entry *entry, ext4_lblk_t value)
{
    entry->block = cpu_to_le32(value);
}

static inline unsigned dx_get_hash(struct dx_entry *entry)
{
    return le32_to_cpu(entry->hash);
}

static inline void dx_set_hash(struct dx_entry *entry, unsigned value)
{
    entry->hash = cpu_to_le32(value);
}

static inline unsigned dx_get_count(struct dx_entry *entries)
{
    return le16_to_cpu(((struct dx_countlimit *) entries)->count);
}

static inline unsigned dx_get_limit(struct dx_entry *entries)
{
    return le16_to_cpu(((struct dx_countlimit *) entries)->limit);
}

static inline void dx_set_count(struct dx_entry *entries, unsigned value)
{
    ((struct dx_countlimit *) entries)->count = cpu_to_le16(value);
}

static inline void dx_set_limit(struct dx_entry *entries, unsigned value)
{
    ((struct dx_countlimit *) entries)->limit = cpu_to_le16(value);
}

static inline unsigned dx_root_limit(struct inode *dir, unsigned infosize)
{
    unsigned entry_space = dir->i_sb->s_blocksize - EXT4_DIR_REC_LEN(1) -
        EXT4_DIR_REC_LEN(2) - infosize;

    if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        entry_space -= sizeof(struct dx_tail);
    return entry_space / sizeof(struct dx_entry);
}

static inline unsigned dx_node_limit(struct inode *dir)
{
    unsigned entry_space = dir->i_sb->s_blocksize - EXT4_DIR_REC_LEN(0);

    if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        entry_space -= sizeof(struct dx_tail);
    return entry_space / sizeof(struct dx_entry);
}

/*
 * Debug
 */
#ifdef DX_DEBUG
static void dx_show_index(char * label, struct dx_entry *entries)
{
    int i, n = dx_get_count (entries);
    printk(KERN_DEBUG "%s index ", label);
    for (i = 0; i < n; i++) {
        printk("%x->%lu ", i ? dx_get_hash(entries + i) :
                0, (unsigned long)dx_get_block(entries + i));
    }
    printk("\n");
}

struct stats
{
    unsigned names;
    unsigned space;
    unsigned bcount;
};

static struct stats dx_show_leaf(struct dx_hash_info *hinfo, struct ext4_dir_entry_2 *de,
                 int size, int show_names)
{
    unsigned names = 0, space = 0;
    char *base = (char *) de;
    struct dx_hash_info h = *hinfo;

    printk("names: ");
    while ((char *) de < base + size)
    {
        if (de->inode)
        {
            if (show_names)
            {
                int len = de->name_len;
                char *name = de->name;
                while (len--) printk("%c", *name++);
                ext4fs_dirhash(de->name, de->name_len, &h);
                printk(":%x.%u ", h.hash,
                       (unsigned) ((char *) de - base));
            }
            space += EXT4_DIR_REC_LEN(de->name_len);
            names++;
        }
        de = ext4_next_entry(de, size);
    }
    printk("(%i)\n", names);
    return (struct stats) { names, space, 1 };
}

struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir,
                 struct dx_entry *entries, int levels)
{
    unsigned blocksize = dir->i_sb->s_blocksize;
    unsigned count = dx_get_count(entries), names = 0, space = 0, i;
    unsigned bcount = 0;
    struct buffer_head *bh;
    int err;
    printk("%i indexed blocks...\n", count);
    for (i = 0; i < count; i++, entries++)
    {
        ext4_lblk_t block = dx_get_block(entries);
        ext4_lblk_t hash  = i ? dx_get_hash(entries): 0;
        u32 range = i < count - 1? (dx_get_hash(entries + 1) - hash): ~hash;
        struct stats stats;
        printk("%s%3u:%03u hash %8x/%8x ",levels?"":"   ", i, block, hash, range);
        if (!(bh = ext4_bread (NULL,dir, block, 0,&err))) continue;
        stats = levels?
           dx_show_entries(hinfo, dir, ((struct dx_node *) bh->b_data)->entries, levels - 1):
           dx_show_leaf(hinfo, (struct ext4_dir_entry_2 *) bh->b_data, blocksize, 0);
        names += stats.names;
        space += stats.space;
        bcount += stats.bcount;
        brelse(bh);
    }
    if (bcount)
        printk(KERN_DEBUG "%snames %u, fullness %u (%u%%)\n",
               levels ? "" : "   ", names, space/bcount,
               (space/bcount)*100/blocksize);
    return (struct stats) { names, space, bcount};
}
#endif /* DX_DEBUG */

/*
 * Probe for a directory leaf block to search.
 *
 * dx_probe can return ERR_BAD_DX_DIR, which means there was a format
 * error in the directory index, and the caller should fall back to
 * searching the directory normally.  The callers of dx_probe **MUST**
 * check for this error code, and make sure it never gets reflected
 * back to userspace.
 */
static struct dx_frame *
dx_probe(const struct qstr *d_name, struct inode *dir,
     struct dx_hash_info *hinfo, struct dx_frame *frame_in, int *err)
{
    unsigned count, indirect;
    struct dx_entry *at, *entries, *p, *q, *m;
    struct dx_root *root;
    struct buffer_head *bh;
    struct dx_frame *frame = frame_in;
    u32 hash;

    frame->bh = NULL;
    if (!(bh = ext4_bread(NULL, dir, 0, 0, err))) {
        if (*err == 0)
            *err = ERR_BAD_DX_DIR;
        goto fail;
    }
    root = (struct dx_root *) bh->b_data;
    if (root->info.hash_version != DX_HASH_TEA &&
        root->info.hash_version != DX_HASH_HALF_MD4 &&
        root->info.hash_version != DX_HASH_LEGACY) {
        ext4_warning(dir->i_sb, "Unrecognised inode hash code %d",
                 root->info.hash_version);
        brelse(bh);
        *err = ERR_BAD_DX_DIR;
        goto fail;
    }
    hinfo->hash_version = root->info.hash_version;
    if (hinfo->hash_version <= DX_HASH_TEA)
        hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
    hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
    if (d_name)
        ext4fs_dirhash(d_name->name, d_name->len, hinfo);
    hash = hinfo->hash;

    if (root->info.unused_flags & 1) {
        ext4_warning(dir->i_sb, "Unimplemented inode hash flags: %#06x",
                 root->info.unused_flags);
        brelse(bh);
        *err = ERR_BAD_DX_DIR;
        goto fail;
    }

    if ((indirect = root->info.indirect_levels) > 1) {
        ext4_warning(dir->i_sb, "Unimplemented inode hash depth: %#06x",
                 root->info.indirect_levels);
        brelse(bh);
        *err = ERR_BAD_DX_DIR;
        goto fail;
    }

    if (!buffer_verified(bh) &&
        !ext4_dx_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data)) {
        ext4_warning(dir->i_sb, "Root failed checksum");
        brelse(bh);
        *err = ERR_BAD_DX_DIR;
        goto fail;
    }
    set_buffer_verified(bh);

    entries = (struct dx_entry *) (((char *)&root->info) +
                       root->info.info_length);

    if (dx_get_limit(entries) != dx_root_limit(dir,
                           root->info.info_length)) {
        ext4_warning(dir->i_sb, "dx entry: limit != root limit");
        brelse(bh);
        *err = ERR_BAD_DX_DIR;
        goto fail;
    }

    dxtrace(printk("Look up %x", hash));
    while (1)
    {
        count = dx_get_count(entries);
        if (!count || count > dx_get_limit(entries)) {
            ext4_warning(dir->i_sb,
                     "dx entry: no count or count > limit");
            brelse(bh);
            *err = ERR_BAD_DX_DIR;
            goto fail2;
        }

        p = entries + 1;
        q = entries + count - 1;
        while (p <= q)
        {
            m = p + (q - p)/2;
            dxtrace(printk("."));
            if (dx_get_hash(m) > hash)
                q = m - 1;
            else
                p = m + 1;
        }

        if (0) // linear search cross check
        {
            unsigned n = count - 1;
            at = entries;
            while (n--)
            {
                dxtrace(printk(","));
                if (dx_get_hash(++at) > hash)
                {
                    at--;
                    break;
                }
            }
            assert (at == p - 1);
        }

        at = p - 1;
        dxtrace(printk(" %x->%u\n", at == entries? 0: dx_get_hash(at), dx_get_block(at)));
        frame->bh = bh;
        frame->entries = entries;
        frame->at = at;
        if (!indirect--) return frame;
        if (!(bh = ext4_bread(NULL, dir, dx_get_block(at), 0, err))) {
            if (!(*err))
                *err = ERR_BAD_DX_DIR;
            goto fail2;
        }
        at = entries = ((struct dx_node *) bh->b_data)->entries;

        if (!buffer_verified(bh) &&
            !ext4_dx_csum_verify(dir,
                     (struct ext4_dir_entry *)bh->b_data)) {
            ext4_warning(dir->i_sb, "Node failed checksum");
            brelse(bh);
            *err = ERR_BAD_DX_DIR;
            goto fail;
        }
        set_buffer_verified(bh);

        if (dx_get_limit(entries) != dx_node_limit (dir)) {
            ext4_warning(dir->i_sb,
                     "dx entry: limit != node limit");
            brelse(bh);
            *err = ERR_BAD_DX_DIR;
            goto fail2;
        }
        frame++;
        frame->bh = NULL;
    }
fail2:
    while (frame >= frame_in) {
        brelse(frame->bh);
        frame--;
    }
fail:
    if (*err == ERR_BAD_DX_DIR)
        ext4_warning(dir->i_sb,
                 "Corrupt dir inode %lu, running e2fsck is "
                 "recommended.", dir->i_ino);
    return NULL;
}

static void dx_release (struct dx_frame *frames)
{
    if (frames[0].bh == NULL)
        return;

    if (((struct dx_root *) frames[0].bh->b_data)->info.indirect_levels)
        brelse(frames[1].bh);
    brelse(frames[0].bh);
}

/*
 * This function increments the frame pointer to search the next leaf
 * block, and reads in the necessary intervening nodes if the search
 * should be necessary.  Whether or not the search is necessary is
 * controlled by the hash parameter.  If the hash value is even, then
 * the search is only continued if the next block starts with that
 * hash value.  This is used if we are searching for a specific file.
 *
 * If the hash value is HASH_NB_ALWAYS, then always go to the next block.
 *
 * This function returns 1 if the caller should continue to search,
 * or 0 if it should not.  If there is an error reading one of the
 * index blocks, it will a negative error code.
 *
 * If start_hash is non-null, it will be filled in with the starting
 * hash of the next page.
 */
static int ext4_htree_next_block(struct inode *dir, __u32 hash,
                 struct dx_frame *frame,
                 struct dx_frame *frames,
                 __u32 *start_hash)
{
    struct dx_frame *p;
    struct buffer_head *bh;
    int err, num_frames = 0;
    __u32 bhash;

    p = frame;
    /*
     * Find the next leaf page by incrementing the frame pointer.
     * If we run out of entries in the interior node, loop around and
     * increment pointer in the parent node.  When we break out of
     * this loop, num_frames indicates the number of interior
     * nodes need to be read.
     */
    while (1) {
        if (++(p->at) < p->entries + dx_get_count(p->entries))
            break;
        if (p == frames)
            return 0;
        num_frames++;
        p--;
    }

    /*
     * If the hash is 1, then continue only if the next page has a
     * continuation hash of any value.  This is used for readdir
     * handling.  Otherwise, check to see if the hash matches the
     * desired contiuation hash.  If it doesn't, return since
     * there's no point to read in the successive index pages.
     */
    bhash = dx_get_hash(p->at);
    if (start_hash)
        *start_hash = bhash;
    if ((hash & 1) == 0) {
        if ((bhash & ~1) != hash)
            return 0;
    }
    /*
     * If the hash is HASH_NB_ALWAYS, we always go to the next
     * block so no check is necessary
     */
    while (num_frames--) {
        if (!(bh = ext4_bread(NULL, dir, dx_get_block(p->at),
                      0, &err))) {
            if (!err) {
                ext4_error(dir->i_sb,
                       "Directory hole detected on inode %lu\n",
                       dir->i_ino);
                return -EIO;
            }
            return err; /* Failure */
        }

        if (!buffer_verified(bh) &&
            !ext4_dx_csum_verify(dir,
                     (struct ext4_dir_entry *)bh->b_data)) {
            ext4_warning(dir->i_sb, "Node failed checksum");
            return -EIO;
        }
        set_buffer_verified(bh);

        p++;
        brelse(p->bh);
        p->bh = bh;
        p->at = p->entries = ((struct dx_node *) bh->b_data)->entries;
    }
    return 1;
}


/*
 * This function fills a red-black tree with information from a
 * directory block.  It returns the number directory entries loaded
 * into the tree.  If there is an error it is returned in err.
 */
static int htree_dirblock_to_tree(struct file *dir_file,
                  struct inode *dir, ext4_lblk_t block,
                  struct dx_hash_info *hinfo,
                  __u32 start_hash, __u32 start_minor_hash)
{
    struct buffer_head *bh;
    struct ext4_dir_entry_2 *de, *top;
    int err = 0, count = 0;

    dxtrace(printk(KERN_INFO "In htree dirblock_to_tree: block %lu\n",
                            (unsigned long)block));
    if (!(bh = ext4_bread(NULL, dir, block, 0, &err))) {
        if (!err) {
            err = -EIO;
            ext4_error(dir->i_sb,
                   "Directory hole detected on inode %lu\n",
                   dir->i_ino);
        }
        return err;
    }

    if (!buffer_verified(bh) &&
        !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))
        return -EIO;
    set_buffer_verified(bh);

    de = (struct ext4_dir_entry_2 *) bh->b_data;
    top = (struct ext4_dir_entry_2 *) ((char *) de +
                       dir->i_sb->s_blocksize -
                       EXT4_DIR_REC_LEN(0));
    for (; de < top; de = ext4_next_entry(de, dir->i_sb->s_blocksize)) {
        if (ext4_check_dir_entry(dir, NULL, de, bh,
                (block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
                     + ((char *)de - bh->b_data))) {
            /* On error, skip the f_pos to the next block. */
            dir_file->f_pos = (dir_file->f_pos |
                    (dir->i_sb->s_blocksize - 1)) + 1;
            brelse(bh);
            return count;
        }
        ext4fs_dirhash(de->name, de->name_len, hinfo);
        if ((hinfo->hash < start_hash) ||
            ((hinfo->hash == start_hash) &&
             (hinfo->minor_hash < start_minor_hash)))
            continue;
        if (de->inode == 0)
            continue;
        if ((err = ext4_htree_store_dirent(dir_file,
                   hinfo->hash, hinfo->minor_hash, de)) != 0) {
            brelse(bh);
            return err;
        }
        count++;
    }
    brelse(bh);
    return count;
}


/*
 * This function fills a red-black tree with information from a
 * directory.  We start scanning the directory in hash order, starting
 * at start_hash and start_minor_hash.
 *
 * This function returns the number of entries inserted into the tree,
 * or a negative error code.
 */
int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash,
             __u32 start_minor_hash, __u32 *next_hash)
{
    struct dx_hash_info hinfo;
    struct ext4_dir_entry_2 *de;
    struct dx_frame frames[2], *frame;
    struct inode *dir;
    ext4_lblk_t block;
    int count = 0;
    int ret, err;
    __u32 hashval;

    dxtrace(printk(KERN_DEBUG "In htree_fill_tree, start hash: %x:%x\n",
               start_hash, start_minor_hash));
    dir = dir_file->f_path.dentry->d_inode;
    if (!(ext4_test_inode_flag(dir, EXT4_INODE_INDEX))) {
        hinfo.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
        if (hinfo.hash_version <= DX_HASH_TEA)
            hinfo.hash_version +=
                EXT4_SB(dir->i_sb)->s_hash_unsigned;
        hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
        count = htree_dirblock_to_tree(dir_file, dir, 0, &hinfo,
                           start_hash, start_minor_hash);
        *next_hash = ~0;
        return count;
    }
    hinfo.hash = start_hash;
    hinfo.minor_hash = 0;
    frame = dx_probe(NULL, dir, &hinfo, frames, &err);
    if (!frame)
        return err;

    /* Add '.' and '..' from the htree header */
    if (!start_hash && !start_minor_hash) {
        de = (struct ext4_dir_entry_2 *) frames[0].bh->b_data;
        if ((err = ext4_htree_store_dirent(dir_file, 0, 0, de)) != 0)
            goto errout;
        count++;
    }
    if (start_hash < 2 || (start_hash ==2 && start_minor_hash==0)) {
        de = (struct ext4_dir_entry_2 *) frames[0].bh->b_data;
        de = ext4_next_entry(de, dir->i_sb->s_blocksize);
        if ((err = ext4_htree_store_dirent(dir_file, 2, 0, de)) != 0)
            goto errout;
        count++;
    }

    while (1) {
        block = dx_get_block(frame->at);
        ret = htree_dirblock_to_tree(dir_file, dir, block, &hinfo,
                         start_hash, start_minor_hash);
        if (ret < 0) {
            err = ret;
            goto errout;
        }
        count += ret;
        hashval = ~0;
        ret = ext4_htree_next_block(dir, HASH_NB_ALWAYS,
                        frame, frames, &hashval);
        *next_hash = hashval;
        if (ret < 0) {
            err = ret;
            goto errout;
        }
        /*
         * Stop if:  (a) there are no more entries, or
         * (b) we have inserted at least one entry and the
         * next hash value is not a continuation
         */
        if ((ret == 0) ||
            (count && ((hashval & 1) == 0)))
            break;
    }
    dx_release(frames);
    dxtrace(printk(KERN_DEBUG "Fill tree: returned %d entries, "
               "next hash: %x\n", count, *next_hash));
    return count;
errout:
    dx_release(frames);
    return (err);
}


/*
 * Directory block splitting, compacting
 */

/*
 * Create map of hash values, offsets, and sizes, stored at end of block.
 * Returns number of entries mapped.
 */
static int dx_make_map(struct ext4_dir_entry_2 *de, unsigned blocksize,
               struct dx_hash_info *hinfo,
               struct dx_map_entry *map_tail)
{
    int count = 0;
    char *base = (char *) de;
    struct dx_hash_info h = *hinfo;

    while ((char *) de < base + blocksize) {
        if (de->name_len && de->inode) {
            ext4fs_dirhash(de->name, de->name_len, &h);
            map_tail--;
            map_tail->hash = h.hash;
            map_tail->offs = ((char *) de - base)>>2;
            map_tail->size = le16_to_cpu(de->rec_len);
            count++;
            cond_resched();
        }
        /* XXX: do we need to check rec_len == 0 case? -Chris */
        de = ext4_next_entry(de, blocksize);
    }
    return count;
}

/* Sort map by hash value */
static void dx_sort_map (struct dx_map_entry *map, unsigned count)
{
    struct dx_map_entry *p, *q, *top = map + count - 1;
    int more;
    /* Combsort until bubble sort doesn't suck */
    while (count > 2) {
        count = count*10/13;
        if (count - 9 < 2) /* 9, 10 -> 11 */
            count = 11;
        for (p = top, q = p - count; q >= map; p--, q--)
            if (p->hash < q->hash)
                swap(*p, *q);
    }
    /* Garden variety bubble sort */
    do {
        more = 0;
        q = top;
        while (q-- > map) {
            if (q[1].hash >= q[0].hash)
                continue;
            swap(*(q+1), *q);
            more = 1;
        }
    } while(more);
}

static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
{
    struct dx_entry *entries = frame->entries;
    struct dx_entry *old = frame->at, *new = old + 1;
    int count = dx_get_count(entries);

    assert(count < dx_get_limit(entries));
    assert(old < entries + count);
    memmove(new + 1, new, (char *)(entries + count) - (char *)(new));
    dx_set_hash(new, hash);
    dx_set_block(new, block);
    dx_set_count(entries, count + 1);
}

static void ext4_update_dx_flag(struct inode *inode)
{
    if (!EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
                     EXT4_FEATURE_COMPAT_DIR_INDEX))
        ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
}

/*
 * NOTE! unlike strncmp, ext4_match returns 1 for success, 0 for failure.
 *
 * `len <= EXT4_NAME_LEN' is guaranteed by caller.
 * `de != NULL' is guaranteed by caller.
 */
static inline int ext4_match (int len, const char * const name,
                  struct ext4_dir_entry_2 * de)
{
    if (len != de->name_len)
        return 0;
    if (!de->inode)
        return 0;
    return !memcmp(name, de->name, len);
}

/*
 * Returns 0 if not found, -1 on failure, and 1 on success
 */
static inline int search_dirblock(struct buffer_head *bh,
                  struct inode *dir,
                  const struct qstr *d_name,
                  unsigned int offset,
                  struct ext4_dir_entry_2 ** res_dir)
{
    struct ext4_dir_entry_2 * de;
    char * dlimit;
    int de_len;
    const char *name = d_name->name;
    int namelen = d_name->len;

    de = (struct ext4_dir_entry_2 *) bh->b_data;
    dlimit = bh->b_data + dir->i_sb->s_blocksize;
    while ((char *) de < dlimit) {
        /* this code is executed quadratically often */
        /* do minimal checking `by hand' */

        if ((char *) de + namelen <= dlimit &&
            ext4_match (namelen, name, de)) {
            /* found a match - just to be sure, do a full check */
            if (ext4_check_dir_entry(dir, NULL, de, bh, offset))
                return -1;
            *res_dir = de;
            return 1;
        }
        /* prevent looping on a bad block */
        de_len = ext4_rec_len_from_disk(de->rec_len,
                        dir->i_sb->s_blocksize);
        if (de_len <= 0)
            return -1;
        offset += de_len;
        de = (struct ext4_dir_entry_2 *) ((char *) de + de_len);
    }
    return 0;
}


/*
 *  ext4_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the cache buffer in which the entry was found, and the entry
 * itself (as a parameter - res_dir). It does NOT read the inode of the
 * entry - you'll have to do that yourself if you want to.
 *
 * The returned buffer_head has ->b_count elevated.  The caller is expected
 * to brelse() it when appropriate.
 */
static struct buffer_head * ext4_find_entry (struct inode *dir,
                    const struct qstr *d_name,
                    struct ext4_dir_entry_2 ** res_dir)
{
    struct super_block *sb;
    struct buffer_head *bh_use[NAMEI_RA_SIZE];
    struct buffer_head *bh, *ret = NULL;
    ext4_lblk_t start, block, b;
    const u8 *name = d_name->name;
    int ra_max = 0;     /* Number of bh's in the readahead
                   buffer, bh_use[] */
    int ra_ptr = 0;     /* Current index into readahead
                   buffer */
    int num = 0;
    ext4_lblk_t  nblocks;
    int i, err;
    int namelen;

    *res_dir = NULL;
    sb = dir->i_sb;
    namelen = d_name->len;
    if (namelen > EXT4_NAME_LEN)
        return NULL;
    if ((namelen <= 2) && (name[0] == '.') &&
        (name[1] == '.' || name[1] == '\0')) {
        /*
         * "." or ".." will only be in the first block
         * NFS may look up ".."; "." should be handled by the VFS
         */
        block = start = 0;
        nblocks = 1;
        goto restart;
    }
    if (is_dx(dir)) {
        bh = ext4_dx_find_entry(dir, d_name, res_dir, &err);
        /*
         * On success, or if the error was file not found,
         * return.  Otherwise, fall back to doing a search the
         * old fashioned way.
         */
        if (bh || (err != ERR_BAD_DX_DIR))
            return bh;
        dxtrace(printk(KERN_DEBUG "ext4_find_entry: dx failed, "
                   "falling back\n"));
    }
    nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb);
    start = EXT4_I(dir)->i_dir_start_lookup;
    if (start >= nblocks)
        start = 0;
    block = start;
restart:
    do {
        /*
         * We deal with the read-ahead logic here.
         */
        if (ra_ptr >= ra_max) {
            /* Refill the readahead buffer */
            ra_ptr = 0;
            b = block;
            for (ra_max = 0; ra_max < NAMEI_RA_SIZE; ra_max++) {
                /*
                 * Terminate if we reach the end of the
                 * directory and must wrap, or if our
                 * search has finished at this block.
                 */
                if (b >= nblocks || (num && block == start)) {
                    bh_use[ra_max] = NULL;
                    break;
                }
                num++;
                bh = ext4_getblk(NULL, dir, b++, 0, &err);
                bh_use[ra_max] = bh;
                if (bh)
                    ll_rw_block(READ | REQ_META | REQ_PRIO,
                            1, &bh);
            }
        }
        if ((bh = bh_use[ra_ptr++]) == NULL)
            goto next;
        wait_on_buffer(bh);
        if (!buffer_uptodate(bh)) {
            /* read error, skip block & hope for the best */
            EXT4_ERROR_INODE(dir, "reading directory lblock %lu",
                     (unsigned long) block);
            brelse(bh);
            goto next;
        }
        if (!buffer_verified(bh) &&
            !ext4_dirent_csum_verify(dir,
                (struct ext4_dir_entry *)bh->b_data)) {
            EXT4_ERROR_INODE(dir, "checksumming directory "
                     "block %lu", (unsigned long)block);
            brelse(bh);
            goto next;
        }
        set_buffer_verified(bh);
        i = search_dirblock(bh, dir, d_name,
                block << EXT4_BLOCK_SIZE_BITS(sb), res_dir);
        if (i == 1) {
            EXT4_I(dir)->i_dir_start_lookup = block;
            ret = bh;
            goto cleanup_and_exit;
        } else {
            brelse(bh);
            if (i < 0)
                goto cleanup_and_exit;
        }
    next:
        if (++block >= nblocks)
            block = 0;
    } while (block != start);

    /*
     * If the directory has grown while we were searching, then
     * search the last part of the directory before giving up.
     */
    block = nblocks;
    nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb);
    if (block < nblocks) {
        start = 0;
        goto restart;
    }

cleanup_and_exit:
    /* Clean up the read-ahead blocks */
    for (; ra_ptr < ra_max; ra_ptr++)
        brelse(bh_use[ra_ptr]);
    return ret;
}

static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct qstr *d_name,
               struct ext4_dir_entry_2 **res_dir, int *err)
{
    struct super_block * sb = dir->i_sb;
    struct dx_hash_info hinfo;
    struct dx_frame frames[2], *frame;
    struct buffer_head *bh;
    ext4_lblk_t block;
    int retval;

    if (!(frame = dx_probe(d_name, dir, &hinfo, frames, err)))
        return NULL;
    do {
        block = dx_get_block(frame->at);
        if (!(bh = ext4_bread(NULL, dir, block, 0, err))) {
            if (!(*err)) {
                *err = -EIO;
                ext4_error(dir->i_sb,
                       "Directory hole detected on inode %lu\n",
                       dir->i_ino);
            }
            goto errout;
        }

        if (!buffer_verified(bh) &&
            !ext4_dirent_csum_verify(dir,
                (struct ext4_dir_entry *)bh->b_data)) {
            EXT4_ERROR_INODE(dir, "checksumming directory "
                     "block %lu", (unsigned long)block);
            brelse(bh);
            *err = -EIO;
            goto errout;
        }
        set_buffer_verified(bh);
        retval = search_dirblock(bh, dir, d_name,
                     block << EXT4_BLOCK_SIZE_BITS(sb),
                     res_dir);
        if (retval == 1) {  /* Success! */
            dx_release(frames);
            return bh;
        }
        brelse(bh);
        if (retval == -1) {
            *err = ERR_BAD_DX_DIR;
            goto errout;
        }

        /* Check to see if we should continue to search */
        retval = ext4_htree_next_block(dir, hinfo.hash, frame,
                           frames, NULL);
        if (retval < 0) {
            ext4_warning(sb,
                 "error reading index page in directory #%lu",
                 dir->i_ino);
            *err = retval;
            goto errout;
        }
    } while (retval == 1);

    *err = -ENOENT;
errout:
    dxtrace(printk(KERN_DEBUG "%s not found\n", d_name->name));
    dx_release (frames);
    return NULL;
}

static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
    struct inode *inode;
    struct ext4_dir_entry_2 *de;
    struct buffer_head *bh;

    if (dentry->d_name.len > EXT4_NAME_LEN)
        return ERR_PTR(-ENAMETOOLONG);

    bh = ext4_find_entry(dir, &dentry->d_name, &de);
    inode = NULL;
    if (bh) {
        __u32 ino = le32_to_cpu(de->inode);
        brelse(bh);
        if (!ext4_valid_inum(dir->i_sb, ino)) {
            EXT4_ERROR_INODE(dir, "bad inode number: %u", ino);
            return ERR_PTR(-EIO);
        }
        if (unlikely(ino == dir->i_ino)) {
            EXT4_ERROR_INODE(dir, "'%.*s' linked to parent dir",
                     dentry->d_name.len,
                     dentry->d_name.name);
            return ERR_PTR(-EIO);
        }
        inode = ext4_iget(dir->i_sb, ino);
        if (inode == ERR_PTR(-ESTALE)) {
            EXT4_ERROR_INODE(dir,
                     "deleted inode referenced: %u",
                     ino);
            return ERR_PTR(-EIO);
        }
    }
    return d_splice_alias(inode, dentry);
}


struct dentry *ext4_get_parent(struct dentry *child)
{
    __u32 ino;
    static const struct qstr dotdot = QSTR_INIT("..", 2);
    struct ext4_dir_entry_2 * de;
    struct buffer_head *bh;

    bh = ext4_find_entry(child->d_inode, &dotdot, &de);
    if (!bh)
        return ERR_PTR(-ENOENT);
    ino = le32_to_cpu(de->inode);
    brelse(bh);

    if (!ext4_valid_inum(child->d_inode->i_sb, ino)) {
        EXT4_ERROR_INODE(child->d_inode,
                 "bad parent inode number: %u", ino);
        return ERR_PTR(-EIO);
    }

    return d_obtain_alias(ext4_iget(child->d_inode->i_sb, ino));
}

#define S_SHIFT 12
static unsigned char ext4_type_by_mode[S_IFMT >> S_SHIFT] = {
    [S_IFREG >> S_SHIFT]    = EXT4_FT_REG_FILE,
    [S_IFDIR >> S_SHIFT]    = EXT4_FT_DIR,
    [S_IFCHR >> S_SHIFT]    = EXT4_FT_CHRDEV,
    [S_IFBLK >> S_SHIFT]    = EXT4_FT_BLKDEV,
    [S_IFIFO >> S_SHIFT]    = EXT4_FT_FIFO,
    [S_IFSOCK >> S_SHIFT]   = EXT4_FT_SOCK,
    [S_IFLNK >> S_SHIFT]    = EXT4_FT_SYMLINK,
};

static inline void ext4_set_de_type(struct super_block *sb,
                struct ext4_dir_entry_2 *de,
                umode_t mode) {
    if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE))
        de->file_type = ext4_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
}

/*
 * Move count entries from end of map between two memory locations.
 * Returns pointer to last entry moved.
 */
static struct ext4_dir_entry_2 *
dx_move_dirents(char *from, char *to, struct dx_map_entry *map, int count,
        unsigned blocksize)
{
    unsigned rec_len = 0;

    while (count--) {
        struct ext4_dir_entry_2 *de = (struct ext4_dir_entry_2 *)
                        (from + (map->offs<<2));
        rec_len = EXT4_DIR_REC_LEN(de->name_len);
        memcpy (to, de, rec_len);
        ((struct ext4_dir_entry_2 *) to)->rec_len =
                ext4_rec_len_to_disk(rec_len, blocksize);
        de->inode = 0;
        map++;
        to += rec_len;
    }
    return (struct ext4_dir_entry_2 *) (to - rec_len);
}

/*
 * Compact each dir entry in the range to the minimal rec_len.
 * Returns pointer to last entry in range.
 */
static struct ext4_dir_entry_2* dx_pack_dirents(char *base, unsigned blocksize)
{
    struct ext4_dir_entry_2 *next, *to, *prev, *de = (struct ext4_dir_entry_2 *) base;
    unsigned rec_len = 0;

    prev = to = de;
    while ((char*)de < base + blocksize) {
        next = ext4_next_entry(de, blocksize);
        if (de->inode && de->name_len) {
            rec_len = EXT4_DIR_REC_LEN(de->name_len);
            if (de > to)
                memmove(to, de, rec_len);
            to->rec_len = ext4_rec_len_to_disk(rec_len, blocksize);
            prev = to;
            to = (struct ext4_dir_entry_2 *) (((char *) to) + rec_len);
        }
        de = next;
    }
    return prev;
}

/*
 * Split a full leaf block to make room for a new dir entry.
 * Allocate a new block, and move entries so that they are approx. equally full.
 * Returns pointer to de in block into which the new entry will be inserted.
 */
static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
            struct buffer_head **bh,struct dx_frame *frame,
            struct dx_hash_info *hinfo, int *error)
{
    unsigned blocksize = dir->i_sb->s_blocksize;
    unsigned count, continued;
    struct buffer_head *bh2;
    ext4_lblk_t newblock;
    u32 hash2;
    struct dx_map_entry *map;
    char *data1 = (*bh)->b_data, *data2;
    unsigned split, move, size;
    struct ext4_dir_entry_2 *de = NULL, *de2;
    struct ext4_dir_entry_tail *t;
    int csum_size = 0;
    int err = 0, i;

    if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        csum_size = sizeof(struct ext4_dir_entry_tail);

    bh2 = ext4_append (handle, dir, &newblock, &err);
    if (!(bh2)) {
        brelse(*bh);
        *bh = NULL;
        goto errout;
    }

    BUFFER_TRACE(*bh, "get_write_access");
    err = ext4_journal_get_write_access(handle, *bh);
    if (err)
        goto journal_error;

    BUFFER_TRACE(frame->bh, "get_write_access");
    err = ext4_journal_get_write_access(handle, frame->bh);
    if (err)
        goto journal_error;

    data2 = bh2->b_data;

    /* create map in the end of data2 block */
    map = (struct dx_map_entry *) (data2 + blocksize);
    count = dx_make_map((struct ext4_dir_entry_2 *) data1,
                 blocksize, hinfo, map);
    map -= count;
    dx_sort_map(map, count);
    /* Split the existing block in the middle, size-wise */
    size = 0;
    move = 0;
    for (i = count-1; i >= 0; i--) {
        /* is more than half of this entry in 2nd half of the block? */
        if (size + map[i].size/2 > blocksize/2)
            break;
        size += map[i].size;
        move++;
    }
    /* map index at which we will split */
    split = count - move;
    hash2 = map[split].hash;
    continued = hash2 == map[split - 1].hash;
    dxtrace(printk(KERN_INFO "Split block %lu at %x, %i/%i\n",
            (unsigned long)dx_get_block(frame->at),
                    hash2, split, count-split));

    /* Fancy dance to stay within two buffers */
    de2 = dx_move_dirents(data1, data2, map + split, count - split, blocksize);
    de = dx_pack_dirents(data1, blocksize);
    de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
                       (char *) de,
                       blocksize);
    de2->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) -
                        (char *) de2,
                        blocksize);
    if (csum_size) {
        t = EXT4_DIRENT_TAIL(data2, blocksize);
        initialize_dirent_tail(t, blocksize);

        t = EXT4_DIRENT_TAIL(data1, blocksize);
        initialize_dirent_tail(t, blocksize);
    }

    dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data1, blocksize, 1));
    dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data2, blocksize, 1));

    /* Which block gets the new entry? */
    if (hinfo->hash >= hash2)
    {
        swap(*bh, bh2);
        de = de2;
    }
    dx_insert_block(frame, hash2 + continued, newblock);
    err = ext4_handle_dirty_dirent_node(handle, dir, bh2);
    if (err)
        goto journal_error;
    err = ext4_handle_dirty_dx_node(handle, dir, frame->bh);
    if (err)
        goto journal_error;
    brelse(bh2);
    dxtrace(dx_show_index("frame", frame->entries));
    return de;

journal_error:
    brelse(*bh);
    brelse(bh2);
    *bh = NULL;
    ext4_std_error(dir->i_sb, err);
errout:
    *error = err;
    return NULL;
}

/*
 * Add a new entry into a directory (leaf) block.  If de is non-NULL,
 * it points to a directory entry which is guaranteed to be large
 * enough for new directory entry.  If de is NULL, then
 * add_dirent_to_buf will attempt search the directory block for
 * space.  It will return -ENOSPC if no space is available, and -EIO
 * and -EEXIST if directory entry already exists.
 */
static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
                 struct inode *inode, struct ext4_dir_entry_2 *de,
                 struct buffer_head *bh)
{
    struct inode    *dir = dentry->d_parent->d_inode;
    const char  *name = dentry->d_name.name;
    int     namelen = dentry->d_name.len;
    unsigned int    offset = 0;
    unsigned int    blocksize = dir->i_sb->s_blocksize;
    unsigned short  reclen;
    int     nlen, rlen, err;
    char        *top;
    int     csum_size = 0;

    if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        csum_size = sizeof(struct ext4_dir_entry_tail);

    reclen = EXT4_DIR_REC_LEN(namelen);
    if (!de) {
        de = (struct ext4_dir_entry_2 *)bh->b_data;
        top = bh->b_data + (blocksize - csum_size) - reclen;
        while ((char *) de <= top) {
            if (ext4_check_dir_entry(dir, NULL, de, bh, offset))
                return -EIO;
            if (ext4_match(namelen, name, de))
                return -EEXIST;
            nlen = EXT4_DIR_REC_LEN(de->name_len);
            rlen = ext4_rec_len_from_disk(de->rec_len, blocksize);
            if ((de->inode? rlen - nlen: rlen) >= reclen)
                break;
            de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
            offset += rlen;
        }
        if ((char *) de > top)
            return -ENOSPC;
    }
    BUFFER_TRACE(bh, "get_write_access");
    err = ext4_journal_get_write_access(handle, bh);
    if (err) {
        ext4_std_error(dir->i_sb, err);
        return err;
    }

    /* By now the buffer is marked for journaling */
    nlen = EXT4_DIR_REC_LEN(de->name_len);
    rlen = ext4_rec_len_from_disk(de->rec_len, blocksize);
    if (de->inode) {
        struct ext4_dir_entry_2 *de1 = (struct ext4_dir_entry_2 *)((char *)de + nlen);
        de1->rec_len = ext4_rec_len_to_disk(rlen - nlen, blocksize);
        de->rec_len = ext4_rec_len_to_disk(nlen, blocksize);
        de = de1;
    }
    de->file_type = EXT4_FT_UNKNOWN;
    de->inode = cpu_to_le32(inode->i_ino);
    ext4_set_de_type(dir->i_sb, de, inode->i_mode);
    de->name_len = namelen;
    memcpy(de->name, name, namelen);
    /*
     * XXX shouldn't update any times until successful
     * completion of syscall, but too many callers depend
     * on this.
     *
     * XXX similarly, too many callers depend on
     * ext4_new_inode() setting the times, but error
     * recovery deletes the inode, so the worst that can
     * happen is that the times are slightly out of date
     * and/or different from the directory change time.
     */
    dir->i_mtime = dir->i_ctime = ext4_current_time(dir);
    ext4_update_dx_flag(dir);
    dir->i_version++;
    ext4_mark_inode_dirty(handle, dir);
    BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
    err = ext4_handle_dirty_dirent_node(handle, dir, bh);
    if (err)
        ext4_std_error(dir->i_sb, err);
    return 0;
}

/*
 * This converts a one block unindexed directory to a 3 block indexed
 * directory, and adds the dentry to the indexed directory.
 */
static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
                struct inode *inode, struct buffer_head *bh)
{
    struct inode    *dir = dentry->d_parent->d_inode;
    const char  *name = dentry->d_name.name;
    int     namelen = dentry->d_name.len;
    struct buffer_head *bh2;
    struct dx_root  *root;
    struct dx_frame frames[2], *frame;
    struct dx_entry *entries;
    struct ext4_dir_entry_2 *de, *de2;
    struct ext4_dir_entry_tail *t;
    char        *data1, *top;
    unsigned    len;
    int     retval;
    unsigned    blocksize;
    struct dx_hash_info hinfo;
    ext4_lblk_t  block;
    struct fake_dirent *fde;
    int     csum_size = 0;

    if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        csum_size = sizeof(struct ext4_dir_entry_tail);

    blocksize =  dir->i_sb->s_blocksize;
    dxtrace(printk(KERN_DEBUG "Creating index: inode %lu\n", dir->i_ino));
    retval = ext4_journal_get_write_access(handle, bh);
    if (retval) {
        ext4_std_error(dir->i_sb, retval);
        brelse(bh);
        return retval;
    }
    root = (struct dx_root *) bh->b_data;

    /* The 0th block becomes the root, move the dirents out */
    fde = &root->dotdot;
    de = (struct ext4_dir_entry_2 *)((char *)fde +
        ext4_rec_len_from_disk(fde->rec_len, blocksize));
    if ((char *) de >= (((char *) root) + blocksize)) {
        EXT4_ERROR_INODE(dir, "invalid rec_len for '..'");
        brelse(bh);
        return -EIO;
    }
    len = ((char *) root) + (blocksize - csum_size) - (char *) de;

    /* Allocate new block for the 0th block's dirents */
    bh2 = ext4_append(handle, dir, &block, &retval);
    if (!(bh2)) {
        brelse(bh);
        return retval;
    }
    ext4_set_inode_flag(dir, EXT4_INODE_INDEX);
    data1 = bh2->b_data;

    memcpy (data1, de, len);
    de = (struct ext4_dir_entry_2 *) data1;
    top = data1 + len;
    while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top)
        de = de2;
    de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
                       (char *) de,
                       blocksize);

    if (csum_size) {
        t = EXT4_DIRENT_TAIL(data1, blocksize);
        initialize_dirent_tail(t, blocksize);
    }

    /* Initialize the root; the dot dirents already exist */
    de = (struct ext4_dir_entry_2 *) (&root->dotdot);
    de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(2),
                       blocksize);
    memset (&root->info, 0, sizeof(root->info));
    root->info.info_length = sizeof(root->info);
    root->info.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
    entries = root->entries;
    dx_set_block(entries, 1);
    dx_set_count(entries, 1);
    dx_set_limit(entries, dx_root_limit(dir, sizeof(root->info)));

    /* Initialize as for dx_probe */
    hinfo.hash_version = root->info.hash_version;
    if (hinfo.hash_version <= DX_HASH_TEA)
        hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
    hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
    ext4fs_dirhash(name, namelen, &hinfo);
    frame = frames;
    frame->entries = entries;
    frame->at = entries;
    frame->bh = bh;
    bh = bh2;

    ext4_handle_dirty_dx_node(handle, dir, frame->bh);
    ext4_handle_dirty_dirent_node(handle, dir, bh);

    de = do_split(handle,dir, &bh, frame, &hinfo, &retval);
    if (!de) {
        /*
         * Even if the block split failed, we have to properly write
         * out all the changes we did so far. Otherwise we can end up
         * with corrupted filesystem.
         */
        ext4_mark_inode_dirty(handle, dir);
        dx_release(frames);
        return retval;
    }
    dx_release(frames);

    retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
    brelse(bh);
    return retval;
}

/*
 *  ext4_add_entry()
 *
 * adds a file entry to the specified directory, using the same
 * semantics as ext4_find_entry(). It returns NULL if it failed.
 *
 * NOTE!! The inode part of 'de' is left at 0 - which means you
 * may not sleep between calling this and putting something into
 * the entry, as someone else might have used it while you slept.
 */
static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
              struct inode *inode)
{
    struct inode *dir = dentry->d_parent->d_inode;
    struct buffer_head *bh;
    struct ext4_dir_entry_2 *de;
    struct ext4_dir_entry_tail *t;
    struct super_block *sb;
    int retval;
    int dx_fallback=0;
    unsigned blocksize;
    ext4_lblk_t block, blocks;
    int csum_size = 0;

    if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        csum_size = sizeof(struct ext4_dir_entry_tail);

    sb = dir->i_sb;
    blocksize = sb->s_blocksize;
    if (!dentry->d_name.len)
        return -EINVAL;
    if (is_dx(dir)) {
        retval = ext4_dx_add_entry(handle, dentry, inode);
        if (!retval || (retval != ERR_BAD_DX_DIR))
            return retval;
        ext4_clear_inode_flag(dir, EXT4_INODE_INDEX);
        dx_fallback++;
        ext4_mark_inode_dirty(handle, dir);
    }
    blocks = dir->i_size >> sb->s_blocksize_bits;
    for (block = 0; block < blocks; block++) {
        if (!(bh = ext4_bread(handle, dir, block, 0, &retval))) {
            if (!retval) {
                retval = -EIO;
                ext4_error(inode->i_sb,
                       "Directory hole detected on inode %lu\n",
                       inode->i_ino);
            }
            return retval;
        }
        if (!buffer_verified(bh) &&
            !ext4_dirent_csum_verify(dir,
                (struct ext4_dir_entry *)bh->b_data))
            return -EIO;
        set_buffer_verified(bh);
        retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
        if (retval != -ENOSPC) {
            brelse(bh);
            return retval;
        }

        if (blocks == 1 && !dx_fallback &&
            EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX))
            return make_indexed_dir(handle, dentry, inode, bh);
        brelse(bh);
    }
    bh = ext4_append(handle, dir, &block, &retval);
    if (!bh)
        return retval;
    de = (struct ext4_dir_entry_2 *) bh->b_data;
    de->inode = 0;
    de->rec_len = ext4_rec_len_to_disk(blocksize - csum_size, blocksize);

    if (csum_size) {
        t = EXT4_DIRENT_TAIL(bh->b_data, blocksize);
        initialize_dirent_tail(t, blocksize);
    }

    retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
    brelse(bh);
    if (retval == 0)
        ext4_set_inode_state(inode, EXT4_STATE_NEWENTRY);
    return retval;
}

/*
 * Returns 0 for success, or a negative error value
 */
static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
                 struct inode *inode)
{
    struct dx_frame frames[2], *frame;
    struct dx_entry *entries, *at;
    struct dx_hash_info hinfo;
    struct buffer_head *bh;
    struct inode *dir = dentry->d_parent->d_inode;
    struct super_block *sb = dir->i_sb;
    struct ext4_dir_entry_2 *de;
    int err;

    frame = dx_probe(&dentry->d_name, dir, &hinfo, frames, &err);
    if (!frame)
        return err;
    entries = frame->entries;
    at = frame->at;

    if (!(bh = ext4_bread(handle, dir, dx_get_block(frame->at), 0, &err))) {
        if (!err) {
            err = -EIO;
            ext4_error(dir->i_sb,
                   "Directory hole detected on inode %lu\n",
                   dir->i_ino);
        }
        goto cleanup;
    }

    if (!buffer_verified(bh) &&
        !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))
        goto journal_error;
    set_buffer_verified(bh);

    BUFFER_TRACE(bh, "get_write_access");
    err = ext4_journal_get_write_access(handle, bh);
    if (err)
        goto journal_error;

    err = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
    if (err != -ENOSPC)
        goto cleanup;

    /* Block full, should compress but for now just split */
    dxtrace(printk(KERN_DEBUG "using %u of %u node entries\n",
               dx_get_count(entries), dx_get_limit(entries)));
    /* Need to split index? */
    if (dx_get_count(entries) == dx_get_limit(entries)) {
        ext4_lblk_t newblock;
        unsigned icount = dx_get_count(entries);
        int levels = frame - frames;
        struct dx_entry *entries2;
        struct dx_node *node2;
        struct buffer_head *bh2;

        if (levels && (dx_get_count(frames->entries) ==
                   dx_get_limit(frames->entries))) {
            ext4_warning(sb, "Directory index full!");
            err = -ENOSPC;
            goto cleanup;
        }
        bh2 = ext4_append (handle, dir, &newblock, &err);
        if (!(bh2))
            goto cleanup;
        node2 = (struct dx_node *)(bh2->b_data);
        entries2 = node2->entries;
        memset(&node2->fake, 0, sizeof(struct fake_dirent));
        node2->fake.rec_len = ext4_rec_len_to_disk(sb->s_blocksize,
                               sb->s_blocksize);
        BUFFER_TRACE(frame->bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, frame->bh);
        if (err)
            goto journal_error;
        if (levels) {
            unsigned icount1 = icount/2, icount2 = icount - icount1;
            unsigned hash2 = dx_get_hash(entries + icount1);
            dxtrace(printk(KERN_DEBUG "Split index %i/%i\n",
                       icount1, icount2));

            BUFFER_TRACE(frame->bh, "get_write_access"); /* index root */
            err = ext4_journal_get_write_access(handle,
                                 frames[0].bh);
            if (err)
                goto journal_error;

            memcpy((char *) entries2, (char *) (entries + icount1),
                   icount2 * sizeof(struct dx_entry));
            dx_set_count(entries, icount1);
            dx_set_count(entries2, icount2);
            dx_set_limit(entries2, dx_node_limit(dir));

            /* Which index block gets the new entry? */
            if (at - entries >= icount1) {
                frame->at = at = at - entries - icount1 + entries2;
                frame->entries = entries = entries2;
                swap(frame->bh, bh2);
            }
            dx_insert_block(frames + 0, hash2, newblock);
            dxtrace(dx_show_index("node", frames[1].entries));
            dxtrace(dx_show_index("node",
                   ((struct dx_node *) bh2->b_data)->entries));
            err = ext4_handle_dirty_dx_node(handle, dir, bh2);
            if (err)
                goto journal_error;
            brelse (bh2);
        } else {
            dxtrace(printk(KERN_DEBUG
                       "Creating second level index...\n"));
            memcpy((char *) entries2, (char *) entries,
                   icount * sizeof(struct dx_entry));
            dx_set_limit(entries2, dx_node_limit(dir));

            /* Set up root */
            dx_set_count(entries, 1);
            dx_set_block(entries + 0, newblock);
            ((struct dx_root *) frames[0].bh->b_data)->info.indirect_levels = 1;

            /* Add new access path frame */
            frame = frames + 1;
            frame->at = at = at - entries + entries2;
            frame->entries = entries = entries2;
            frame->bh = bh2;
            err = ext4_journal_get_write_access(handle,
                                 frame->bh);
            if (err)
                goto journal_error;
        }
        err = ext4_handle_dirty_dx_node(handle, dir, frames[0].bh);
        if (err) {
            ext4_std_error(inode->i_sb, err);
            goto cleanup;
        }
    }
    de = do_split(handle, dir, &bh, frame, &hinfo, &err);
    if (!de)
        goto cleanup;
    err = add_dirent_to_buf(handle, dentry, inode, de, bh);
    goto cleanup;

journal_error:
    ext4_std_error(dir->i_sb, err);
cleanup:
    if (bh)
        brelse(bh);
    dx_release(frames);
    return err;
}

/*
 * ext4_delete_entry deletes a directory entry by merging it with the
 * previous entry
 */
static int ext4_delete_entry(handle_t *handle,
                 struct inode *dir,
                 struct ext4_dir_entry_2 *de_del,
                 struct buffer_head *bh)
{
    struct ext4_dir_entry_2 *de, *pde;
    unsigned int blocksize = dir->i_sb->s_blocksize;
    int csum_size = 0;
    int i, err;

    if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        csum_size = sizeof(struct ext4_dir_entry_tail);

    i = 0;
    pde = NULL;
    de = (struct ext4_dir_entry_2 *) bh->b_data;
    while (i < bh->b_size - csum_size) {
        if (ext4_check_dir_entry(dir, NULL, de, bh, i))
            return -EIO;
        if (de == de_del)  {
            BUFFER_TRACE(bh, "get_write_access");
            err = ext4_journal_get_write_access(handle, bh);
            if (unlikely(err)) {
                ext4_std_error(dir->i_sb, err);
                return err;
            }
            if (pde)
                pde->rec_len = ext4_rec_len_to_disk(
                    ext4_rec_len_from_disk(pde->rec_len,
                                   blocksize) +
                    ext4_rec_len_from_disk(de->rec_len,
                                   blocksize),
                    blocksize);
            else
                de->inode = 0;
            dir->i_version++;
            BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
            err = ext4_handle_dirty_dirent_node(handle, dir, bh);
            if (unlikely(err)) {
                ext4_std_error(dir->i_sb, err);
                return err;
            }
            return 0;
        }
        i += ext4_rec_len_from_disk(de->rec_len, blocksize);
        pde = de;
        de = ext4_next_entry(de, blocksize);
    }
    return -ENOENT;
}

/*
 * DIR_NLINK feature is set if 1) nlinks > EXT4_LINK_MAX or 2) nlinks == 2,
 * since this indicates that nlinks count was previously 1.
 */
static void ext4_inc_count(handle_t *handle, struct inode *inode)
{
    inc_nlink(inode);
    if (is_dx(inode) && inode->i_nlink > 1) {
        /* limit is 16-bit i_links_count */
        if (inode->i_nlink >= EXT4_LINK_MAX || inode->i_nlink == 2) {
            set_nlink(inode, 1);
            EXT4_SET_RO_COMPAT_FEATURE(inode->i_sb,
                          EXT4_FEATURE_RO_COMPAT_DIR_NLINK);
        }
    }
}

/*
 * If a directory had nlink == 1, then we should let it be 1. This indicates
 * directory has >EXT4_LINK_MAX subdirs.
 */
static void ext4_dec_count(handle_t *handle, struct inode *inode)
{
    if (!S_ISDIR(inode->i_mode) || inode->i_nlink > 2)
        drop_nlink(inode);
}


static int ext4_add_nondir(handle_t *handle,
        struct dentry *dentry, struct inode *inode)
{
    int err = ext4_add_entry(handle, dentry, inode);
    if (!err) {
        ext4_mark_inode_dirty(handle, inode);
        unlock_new_inode(inode);
        d_instantiate(dentry, inode);
        return 0;
    }
    drop_nlink(inode);
    unlock_new_inode(inode);
    iput(inode);
    return err;
}

/*
 * By the time this is called, we already have created
 * the directory cache entry for the new file, but it
 * is so far negative - it has no inode.
 *
 * If the create succeeds, we fill in the inode information
 * with d_instantiate().
 */
static int ext4_create(struct inode *dir, struct dentry *dentry, umode_t mode,
               bool excl)
{
    handle_t *handle;
    struct inode *inode;
    int err, retries = 0;

    dquot_initialize(dir);

retry:
    handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                    EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                    EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0, NULL);
    err = PTR_ERR(inode);
    if (!IS_ERR(inode)) {
        inode->i_op = &ext4_file_inode_operations;
        inode->i_fop = &ext4_file_operations;
        ext4_set_aops(inode);
        err = ext4_add_nondir(handle, dentry, inode);
    }
    ext4_journal_stop(handle);
    if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
        goto retry;
    return err;
}

static int ext4_mknod(struct inode *dir, struct dentry *dentry,
              umode_t mode, dev_t rdev)
{
    handle_t *handle;
    struct inode *inode;
    int err, retries = 0;

    if (!new_valid_dev(rdev))
        return -EINVAL;

    dquot_initialize(dir);

retry:
    handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                    EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                    EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0, NULL);
    err = PTR_ERR(inode);
    if (!IS_ERR(inode)) {
        init_special_inode(inode, inode->i_mode, rdev);
        inode->i_op = &ext4_special_inode_operations;
        err = ext4_add_nondir(handle, dentry, inode);
    }
    ext4_journal_stop(handle);
    if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
        goto retry;
    return err;
}

static int ext4_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
    handle_t *handle;
    struct inode *inode;
    struct buffer_head *dir_block = NULL;
    struct ext4_dir_entry_2 *de;
    struct ext4_dir_entry_tail *t;
    unsigned int blocksize = dir->i_sb->s_blocksize;
    int csum_size = 0;
    int err, retries = 0;

    if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
        csum_size = sizeof(struct ext4_dir_entry_tail);

    if (EXT4_DIR_LINK_MAX(dir))
        return -EMLINK;

    dquot_initialize(dir);

retry:
    handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                    EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                    EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    inode = ext4_new_inode(handle, dir, S_IFDIR | mode,
                   &dentry->d_name, 0, NULL);
    err = PTR_ERR(inode);
    if (IS_ERR(inode))
        goto out_stop;

    inode->i_op = &ext4_dir_inode_operations;
    inode->i_fop = &ext4_dir_operations;
    inode->i_size = EXT4_I(inode)->i_disksize = inode->i_sb->s_blocksize;
    if (!(dir_block = ext4_bread(handle, inode, 0, 1, &err))) {
        if (!err) {
            err = -EIO;
            ext4_error(inode->i_sb,
                   "Directory hole detected on inode %lu\n",
                   inode->i_ino);
        }
        goto out_clear_inode;
    }
    BUFFER_TRACE(dir_block, "get_write_access");
    err = ext4_journal_get_write_access(handle, dir_block);
    if (err)
        goto out_clear_inode;
    de = (struct ext4_dir_entry_2 *) dir_block->b_data;
    de->inode = cpu_to_le32(inode->i_ino);
    de->name_len = 1;
    de->rec_len = ext4_rec_len_to_disk(EXT4_DIR_REC_LEN(de->name_len),
                       blocksize);
    strcpy(de->name, ".");
    ext4_set_de_type(dir->i_sb, de, S_IFDIR);
    de = ext4_next_entry(de, blocksize);
    de->inode = cpu_to_le32(dir->i_ino);
    de->rec_len = ext4_rec_len_to_disk(blocksize -
                       (csum_size + EXT4_DIR_REC_LEN(1)),
                       blocksize);
    de->name_len = 2;
    strcpy(de->name, "..");
    ext4_set_de_type(dir->i_sb, de, S_IFDIR);
    set_nlink(inode, 2);

    if (csum_size) {
        t = EXT4_DIRENT_TAIL(dir_block->b_data, blocksize);
        initialize_dirent_tail(t, blocksize);
    }

    BUFFER_TRACE(dir_block, "call ext4_handle_dirty_metadata");
    err = ext4_handle_dirty_dirent_node(handle, inode, dir_block);
    if (err)
        goto out_clear_inode;
    set_buffer_verified(dir_block);
    err = ext4_mark_inode_dirty(handle, inode);
    if (!err)
        err = ext4_add_entry(handle, dentry, inode);
    if (err) {
out_clear_inode:
        clear_nlink(inode);
        unlock_new_inode(inode);
        ext4_mark_inode_dirty(handle, inode);
        iput(inode);
        goto out_stop;
    }
    ext4_inc_count(handle, dir);
    ext4_update_dx_flag(dir);
    err = ext4_mark_inode_dirty(handle, dir);
    if (err)
        goto out_clear_inode;
    unlock_new_inode(inode);
    d_instantiate(dentry, inode);
out_stop:
    brelse(dir_block);
    ext4_journal_stop(handle);
    if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
        goto retry;
    return err;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
static int empty_dir(struct inode *inode)
{
    unsigned int offset;
    struct buffer_head *bh;
    struct ext4_dir_entry_2 *de, *de1;
    struct super_block *sb;
    int err = 0;

    sb = inode->i_sb;
    if (inode->i_size < EXT4_DIR_REC_LEN(1) + EXT4_DIR_REC_LEN(2) ||
        !(bh = ext4_bread(NULL, inode, 0, 0, &err))) {
        if (err)
            EXT4_ERROR_INODE(inode,
                "error %d reading directory lblock 0", err);
        else
            ext4_warning(inode->i_sb,
                     "bad directory (dir #%lu) - no data block",
                     inode->i_ino);
        return 1;
    }
    if (!buffer_verified(bh) &&
        !ext4_dirent_csum_verify(inode,
            (struct ext4_dir_entry *)bh->b_data)) {
        EXT4_ERROR_INODE(inode, "checksum error reading directory "
                 "lblock 0");
        return -EIO;
    }
    set_buffer_verified(bh);
    de = (struct ext4_dir_entry_2 *) bh->b_data;
    de1 = ext4_next_entry(de, sb->s_blocksize);
    if (le32_to_cpu(de->inode) != inode->i_ino ||
            !le32_to_cpu(de1->inode) ||
            strcmp(".", de->name) ||
            strcmp("..", de1->name)) {
        ext4_warning(inode->i_sb,
                 "bad directory (dir #%lu) - no `.' or `..'",
                 inode->i_ino);
        brelse(bh);
        return 1;
    }
    offset = ext4_rec_len_from_disk(de->rec_len, sb->s_blocksize) +
         ext4_rec_len_from_disk(de1->rec_len, sb->s_blocksize);
    de = ext4_next_entry(de1, sb->s_blocksize);
    while (offset < inode->i_size) {
        if (!bh ||
            (void *) de >= (void *) (bh->b_data+sb->s_blocksize)) {
            unsigned int lblock;
            err = 0;
            brelse(bh);
            lblock = offset >> EXT4_BLOCK_SIZE_BITS(sb);
            bh = ext4_bread(NULL, inode, lblock, 0, &err);
            if (!bh) {
                if (err)
                    EXT4_ERROR_INODE(inode,
                        "error %d reading directory "
                        "lblock %u", err, lblock);
                else
                    ext4_warning(inode->i_sb,
                        "bad directory (dir #%lu) - no data block",
                        inode->i_ino);

                offset += sb->s_blocksize;
                continue;
            }
            if (!buffer_verified(bh) &&
                !ext4_dirent_csum_verify(inode,
                    (struct ext4_dir_entry *)bh->b_data)) {
                EXT4_ERROR_INODE(inode, "checksum error "
                         "reading directory lblock 0");
                return -EIO;
            }
            set_buffer_verified(bh);
            de = (struct ext4_dir_entry_2 *) bh->b_data;
        }
        if (ext4_check_dir_entry(inode, NULL, de, bh, offset)) {
            de = (struct ext4_dir_entry_2 *)(bh->b_data +
                             sb->s_blocksize);
            offset = (offset | (sb->s_blocksize - 1)) + 1;
            continue;
        }
        if (le32_to_cpu(de->inode)) {
            brelse(bh);
            return 0;
        }
        offset += ext4_rec_len_from_disk(de->rec_len, sb->s_blocksize);
        de = ext4_next_entry(de, sb->s_blocksize);
    }
    brelse(bh);
    return 1;
}

/* ext4_orphan_add() links an unlinked or truncated inode into a list of
 * such inodes, starting at the superblock, in case we crash before the
 * file is closed/deleted, or in case the inode truncate spans multiple
 * transactions and the last transaction is not recovered after a crash.
 *
 * At filesystem recovery time, we walk this list deleting unlinked
 * inodes and truncating linked inodes in ext4_orphan_cleanup().
 */
int ext4_orphan_add(handle_t *handle, struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    struct ext4_iloc iloc;
    int err = 0, rc;

    if (!EXT4_SB(sb)->s_journal)
        return 0;

    mutex_lock(&EXT4_SB(sb)->s_orphan_lock);
    if (!list_empty(&EXT4_I(inode)->i_orphan))
        goto out_unlock;

    /*
     * Orphan handling is only valid for files with data blocks
     * being truncated, or files being unlinked. Note that we either
     * hold i_mutex, or the inode can not be referenced from outside,
     * so i_nlink should not be bumped due to race
     */
    J_ASSERT((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
          S_ISLNK(inode->i_mode)) || inode->i_nlink == 0);

    BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access");
    err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
    if (err)
        goto out_unlock;

    err = ext4_reserve_inode_write(handle, inode, &iloc);
    if (err)
        goto out_unlock;
    /*
     * Due to previous errors inode may be already a part of on-disk
     * orphan list. If so skip on-disk list modification.
     */
    if (NEXT_ORPHAN(inode) && NEXT_ORPHAN(inode) <=
        (le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count)))
            goto mem_insert;

    /* Insert this inode at the head of the on-disk orphan list... */
    NEXT_ORPHAN(inode) = le32_to_cpu(EXT4_SB(sb)->s_es->s_last_orphan);
    EXT4_SB(sb)->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
    err = ext4_handle_dirty_super(handle, sb);
    rc = ext4_mark_iloc_dirty(handle, inode, &iloc);
    if (!err)
        err = rc;

    /* Only add to the head of the in-memory list if all the
     * previous operations succeeded.  If the orphan_add is going to
     * fail (possibly taking the journal offline), we can't risk
     * leaving the inode on the orphan list: stray orphan-list
     * entries can cause panics at unmount time.
     *
     * This is safe: on error we're going to ignore the orphan list
     * anyway on the next recovery. */
mem_insert:
    if (!err)
        list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);

    jbd_debug(4, "superblock will point to %lu\n", inode->i_ino);
    jbd_debug(4, "orphan inode %lu will point to %d\n",
            inode->i_ino, NEXT_ORPHAN(inode));
out_unlock:
    mutex_unlock(&EXT4_SB(sb)->s_orphan_lock);
    ext4_std_error(inode->i_sb, err);
    return err;
}

/*
 * ext4_orphan_del() removes an unlinked or truncated inode from the list
 * of such inodes stored on disk, because it is finally being cleaned up.
 */
int ext4_orphan_del(handle_t *handle, struct inode *inode)
{
    struct list_head *prev;
    struct ext4_inode_info *ei = EXT4_I(inode);
    struct ext4_sb_info *sbi;
    __u32 ino_next;
    struct ext4_iloc iloc;
    int err = 0;

    if (!EXT4_SB(inode->i_sb)->s_journal)
        return 0;

    mutex_lock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
    if (list_empty(&ei->i_orphan))
        goto out;

    ino_next = NEXT_ORPHAN(inode);
    prev = ei->i_orphan.prev;
    sbi = EXT4_SB(inode->i_sb);

    jbd_debug(4, "remove inode %lu from orphan list\n", inode->i_ino);

    list_del_init(&ei->i_orphan);

    /* If we're on an error path, we may not have a valid
     * transaction handle with which to update the orphan list on
     * disk, but we still need to remove the inode from the linked
     * list in memory. */
    if (!handle)
        goto out;

    err = ext4_reserve_inode_write(handle, inode, &iloc);
    if (err)
        goto out_err;

    if (prev == &sbi->s_orphan) {
        jbd_debug(4, "superblock will point to %u\n", ino_next);
        BUFFER_TRACE(sbi->s_sbh, "get_write_access");
        err = ext4_journal_get_write_access(handle, sbi->s_sbh);
        if (err)
            goto out_brelse;
        sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
        err = ext4_handle_dirty_super(handle, inode->i_sb);
    } else {
        struct ext4_iloc iloc2;
        struct inode *i_prev =
            &list_entry(prev, struct ext4_inode_info, i_orphan)->vfs_inode;

        jbd_debug(4, "orphan inode %lu will point to %u\n",
              i_prev->i_ino, ino_next);
        err = ext4_reserve_inode_write(handle, i_prev, &iloc2);
        if (err)
            goto out_brelse;
        NEXT_ORPHAN(i_prev) = ino_next;
        err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
    }
    if (err)
        goto out_brelse;
    NEXT_ORPHAN(inode) = 0;
    err = ext4_mark_iloc_dirty(handle, inode, &iloc);

out_err:
    ext4_std_error(inode->i_sb, err);
out:
    mutex_unlock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
    return err;

out_brelse:
    brelse(iloc.bh);
    goto out_err;
}

static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
{
    int retval;
    struct inode *inode;
    struct buffer_head *bh;
    struct ext4_dir_entry_2 *de;
    handle_t *handle;

    /* Initialize quotas before so that eventual writes go in
     * separate transaction */
    dquot_initialize(dir);
    dquot_initialize(dentry->d_inode);

    handle = ext4_journal_start(dir, EXT4_DELETE_TRANS_BLOCKS(dir->i_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    retval = -ENOENT;
    bh = ext4_find_entry(dir, &dentry->d_name, &de);
    if (!bh)
        goto end_rmdir;

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    inode = dentry->d_inode;

    retval = -EIO;
    if (le32_to_cpu(de->inode) != inode->i_ino)
        goto end_rmdir;

    retval = -ENOTEMPTY;
    if (!empty_dir(inode))
        goto end_rmdir;

    retval = ext4_delete_entry(handle, dir, de, bh);
    if (retval)
        goto end_rmdir;
    if (!EXT4_DIR_LINK_EMPTY(inode))
        ext4_warning(inode->i_sb,
                 "empty directory has too many links (%d)",
                 inode->i_nlink);
    inode->i_version++;
    clear_nlink(inode);
    /* There's no need to set i_disksize: the fact that i_nlink is
     * zero will ensure that the right thing happens during any
     * recovery. */
    inode->i_size = 0;
    ext4_orphan_add(handle, inode);
    inode->i_ctime = dir->i_ctime = dir->i_mtime = ext4_current_time(inode);
    ext4_mark_inode_dirty(handle, inode);
    ext4_dec_count(handle, dir);
    ext4_update_dx_flag(dir);
    ext4_mark_inode_dirty(handle, dir);

end_rmdir:
    ext4_journal_stop(handle);
    brelse(bh);
    return retval;
}

static int ext4_unlink(struct inode *dir, struct dentry *dentry)
{
    int retval;
    struct inode *inode;
    struct buffer_head *bh;
    struct ext4_dir_entry_2 *de;
    handle_t *handle;

    trace_ext4_unlink_enter(dir, dentry);
    /* Initialize quotas before so that eventual writes go
     * in separate transaction */
    dquot_initialize(dir);
    dquot_initialize(dentry->d_inode);

    handle = ext4_journal_start(dir, EXT4_DELETE_TRANS_BLOCKS(dir->i_sb));
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    retval = -ENOENT;
    bh = ext4_find_entry(dir, &dentry->d_name, &de);
    if (!bh)
        goto end_unlink;

    inode = dentry->d_inode;

    retval = -EIO;
    if (le32_to_cpu(de->inode) != inode->i_ino)
        goto end_unlink;

    if (!inode->i_nlink) {
        ext4_warning(inode->i_sb,
                 "Deleting nonexistent file (%lu), %d",
                 inode->i_ino, inode->i_nlink);
        set_nlink(inode, 1);
    }
    retval = ext4_delete_entry(handle, dir, de, bh);
    if (retval)
        goto end_unlink;
    dir->i_ctime = dir->i_mtime = ext4_current_time(dir);
    ext4_update_dx_flag(dir);
    ext4_mark_inode_dirty(handle, dir);
    drop_nlink(inode);
    if (!inode->i_nlink)
        ext4_orphan_add(handle, inode);
    inode->i_ctime = ext4_current_time(inode);
    ext4_mark_inode_dirty(handle, inode);
    retval = 0;

end_unlink:
    ext4_journal_stop(handle);
    brelse(bh);
    trace_ext4_unlink_exit(dentry, retval);
    return retval;
}

static int ext4_symlink(struct inode *dir,
            struct dentry *dentry, const char *symname)
{
    handle_t *handle;
    struct inode *inode;
    int l, err, retries = 0;
    int credits;

    l = strlen(symname)+1;
    if (l > dir->i_sb->s_blocksize)
        return -ENAMETOOLONG;

    dquot_initialize(dir);

    if (l > EXT4_N_BLOCKS * 4) {
        /*
         * For non-fast symlinks, we just allocate inode and put it on
         * orphan list in the first transaction => we need bitmap,
         * group descriptor, sb, inode block, quota blocks, and
         * possibly selinux xattr blocks.
         */
        credits = 4 + EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
              EXT4_XATTR_TRANS_BLOCKS;
    } else {
        /*
         * Fast symlink. We have to add entry to directory
         * (EXT4_DATA_TRANS_BLOCKS + EXT4_INDEX_EXTRA_TRANS_BLOCKS),
         * allocate new inode (bitmap, group descriptor, inode block,
         * quota blocks, sb is already counted in previous macros).
         */
        credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
              EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
              EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);
    }
retry:
    handle = ext4_journal_start(dir, credits);
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    inode = ext4_new_inode(handle, dir, S_IFLNK|S_IRWXUGO,
                   &dentry->d_name, 0, NULL);
    err = PTR_ERR(inode);
    if (IS_ERR(inode))
        goto out_stop;

    if (l > EXT4_N_BLOCKS * 4) {
        inode->i_op = &ext4_symlink_inode_operations;
        ext4_set_aops(inode);
        /*
         * We cannot call page_symlink() with transaction started
         * because it calls into ext4_write_begin() which can wait
         * for transaction commit if we are running out of space
         * and thus we deadlock. So we have to stop transaction now
         * and restart it when symlink contents is written.
         * 
         * To keep fs consistent in case of crash, we have to put inode
         * to orphan list in the mean time.
         */
        drop_nlink(inode);
        err = ext4_orphan_add(handle, inode);
        ext4_journal_stop(handle);
        if (err)
            goto err_drop_inode;
        err = __page_symlink(inode, symname, l, 1);
        if (err)
            goto err_drop_inode;
        /*
         * Now inode is being linked into dir (EXT4_DATA_TRANS_BLOCKS
         * + EXT4_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified
         */
        handle = ext4_journal_start(dir,
                EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                EXT4_INDEX_EXTRA_TRANS_BLOCKS + 1);
        if (IS_ERR(handle)) {
            err = PTR_ERR(handle);
            goto err_drop_inode;
        }
        set_nlink(inode, 1);
        err = ext4_orphan_del(handle, inode);
        if (err) {
            ext4_journal_stop(handle);
            clear_nlink(inode);
            goto err_drop_inode;
        }
    } else {
        /* clear the extent format for fast symlink */
        ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
        inode->i_op = &ext4_fast_symlink_inode_operations;
        memcpy((char *)&EXT4_I(inode)->i_data, symname, l);
        inode->i_size = l-1;
    }
    EXT4_I(inode)->i_disksize = inode->i_size;
    err = ext4_add_nondir(handle, dentry, inode);
out_stop:
    ext4_journal_stop(handle);
    if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
        goto retry;
    return err;
err_drop_inode:
    unlock_new_inode(inode);
    iput(inode);
    return err;
}

static int ext4_link(struct dentry *old_dentry,
             struct inode *dir, struct dentry *dentry)
{
    handle_t *handle;
    struct inode *inode = old_dentry->d_inode;
    int err, retries = 0;

    if (inode->i_nlink >= EXT4_LINK_MAX)
        return -EMLINK;

    dquot_initialize(dir);

retry:
    handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                    EXT4_INDEX_EXTRA_TRANS_BLOCKS);
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(dir))
        ext4_handle_sync(handle);

    inode->i_ctime = ext4_current_time(inode);
    ext4_inc_count(handle, inode);
    ihold(inode);

    err = ext4_add_entry(handle, dentry, inode);
    if (!err) {
        ext4_mark_inode_dirty(handle, inode);
        d_instantiate(dentry, inode);
    } else {
        drop_nlink(inode);
        iput(inode);
    }
    ext4_journal_stop(handle);
    if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
        goto retry;
    return err;
}

#define PARENT_INO(buffer, size) \
    (ext4_next_entry((struct ext4_dir_entry_2 *)(buffer), size)->inode)

/*
 * Anybody can rename anything with this: the permission checks are left to the
 * higher-level routines.
 */
static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
               struct inode *new_dir, struct dentry *new_dentry)
{
    handle_t *handle;
    struct inode *old_inode, *new_inode;
    struct buffer_head *old_bh, *new_bh, *dir_bh;
    struct ext4_dir_entry_2 *old_de, *new_de;
    int retval, force_da_alloc = 0;

    dquot_initialize(old_dir);
    dquot_initialize(new_dir);

    old_bh = new_bh = dir_bh = NULL;

    /* Initialize quotas before so that eventual writes go
     * in separate transaction */
    if (new_dentry->d_inode)
        dquot_initialize(new_dentry->d_inode);
    handle = ext4_journal_start(old_dir, 2 *
                    EXT4_DATA_TRANS_BLOCKS(old_dir->i_sb) +
                    EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2);
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir))
        ext4_handle_sync(handle);

    old_bh = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de);
    /*
     *  Check for inode number is _not_ due to possible IO errors.
     *  We might rmdir the source, keep it as pwd of some process
     *  and merrily kill the link to whatever was created under the
     *  same name. Goodbye sticky bit ;-<
     */
    old_inode = old_dentry->d_inode;
    retval = -ENOENT;
    if (!old_bh || le32_to_cpu(old_de->inode) != old_inode->i_ino)
        goto end_rename;

    new_inode = new_dentry->d_inode;
    new_bh = ext4_find_entry(new_dir, &new_dentry->d_name, &new_de);
    if (new_bh) {
        if (!new_inode) {
            brelse(new_bh);
            new_bh = NULL;
        }
    }
    if (S_ISDIR(old_inode->i_mode)) {
        if (new_inode) {
            retval = -ENOTEMPTY;
            if (!empty_dir(new_inode))
                goto end_rename;
        }
        retval = -EIO;
        if (!(dir_bh = ext4_bread(handle, old_inode, 0, 0, &retval))) {
            if (!retval) {
                retval = -EIO;
                ext4_error(old_inode->i_sb,
                       "Directory hole detected on inode %lu\n",
                       old_inode->i_ino);
            }
            goto end_rename;
        }
        if (!buffer_verified(dir_bh) &&
            !ext4_dirent_csum_verify(old_inode,
                (struct ext4_dir_entry *)dir_bh->b_data))
            goto end_rename;
        set_buffer_verified(dir_bh);
        if (le32_to_cpu(PARENT_INO(dir_bh->b_data,
                old_dir->i_sb->s_blocksize)) != old_dir->i_ino)
            goto end_rename;
        retval = -EMLINK;
        if (!new_inode && new_dir != old_dir &&
            EXT4_DIR_LINK_MAX(new_dir))
            goto end_rename;
        BUFFER_TRACE(dir_bh, "get_write_access");
        retval = ext4_journal_get_write_access(handle, dir_bh);
        if (retval)
            goto end_rename;
    }
    if (!new_bh) {
        retval = ext4_add_entry(handle, new_dentry, old_inode);
        if (retval)
            goto end_rename;
    } else {
        BUFFER_TRACE(new_bh, "get write access");
        retval = ext4_journal_get_write_access(handle, new_bh);
        if (retval)
            goto end_rename;
        new_de->inode = cpu_to_le32(old_inode->i_ino);
        if (EXT4_HAS_INCOMPAT_FEATURE(new_dir->i_sb,
                          EXT4_FEATURE_INCOMPAT_FILETYPE))
            new_de->file_type = old_de->file_type;
        new_dir->i_version++;
        new_dir->i_ctime = new_dir->i_mtime =
                    ext4_current_time(new_dir);
        ext4_mark_inode_dirty(handle, new_dir);
        BUFFER_TRACE(new_bh, "call ext4_handle_dirty_metadata");
        retval = ext4_handle_dirty_dirent_node(handle, new_dir, new_bh);
        if (unlikely(retval)) {
            ext4_std_error(new_dir->i_sb, retval);
            goto end_rename;
        }
        brelse(new_bh);
        new_bh = NULL;
    }

    /*
     * Like most other Unix systems, set the ctime for inodes on a
     * rename.
     */
    old_inode->i_ctime = ext4_current_time(old_inode);
    ext4_mark_inode_dirty(handle, old_inode);

    /*
     * ok, that's it
     */
    if (le32_to_cpu(old_de->inode) != old_inode->i_ino ||
        old_de->name_len != old_dentry->d_name.len ||
        strncmp(old_de->name, old_dentry->d_name.name, old_de->name_len) ||
        (retval = ext4_delete_entry(handle, old_dir,
                    old_de, old_bh)) == -ENOENT) {
        /* old_de could have moved from under us during htree split, so
         * make sure that we are deleting the right entry.  We might
         * also be pointing to a stale entry in the unused part of
         * old_bh so just checking inum and the name isn't enough. */
        struct buffer_head *old_bh2;
        struct ext4_dir_entry_2 *old_de2;

        old_bh2 = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de2);
        if (old_bh2) {
            retval = ext4_delete_entry(handle, old_dir,
                           old_de2, old_bh2);
            brelse(old_bh2);
        }
    }
    if (retval) {
        ext4_warning(old_dir->i_sb,
                "Deleting old file (%lu), %d, error=%d",
                old_dir->i_ino, old_dir->i_nlink, retval);
    }

    if (new_inode) {
        ext4_dec_count(handle, new_inode);
        new_inode->i_ctime = ext4_current_time(new_inode);
    }
    old_dir->i_ctime = old_dir->i_mtime = ext4_current_time(old_dir);
    ext4_update_dx_flag(old_dir);
    if (dir_bh) {
        PARENT_INO(dir_bh->b_data, new_dir->i_sb->s_blocksize) =
                        cpu_to_le32(new_dir->i_ino);
        BUFFER_TRACE(dir_bh, "call ext4_handle_dirty_metadata");
        if (is_dx(old_inode)) {
            retval = ext4_handle_dirty_dx_node(handle,
                               old_inode,
                               dir_bh);
        } else {
            retval = ext4_handle_dirty_dirent_node(handle,
                                   old_inode,
                                   dir_bh);
        }
        if (retval) {
            ext4_std_error(old_dir->i_sb, retval);
            goto end_rename;
        }
        ext4_dec_count(handle, old_dir);
        if (new_inode) {
            /* checked empty_dir above, can't have another parent,
             * ext4_dec_count() won't work for many-linked dirs */
            clear_nlink(new_inode);
        } else {
            ext4_inc_count(handle, new_dir);
            ext4_update_dx_flag(new_dir);
            ext4_mark_inode_dirty(handle, new_dir);
        }
    }
    ext4_mark_inode_dirty(handle, old_dir);
    if (new_inode) {
        ext4_mark_inode_dirty(handle, new_inode);
        if (!new_inode->i_nlink)
            ext4_orphan_add(handle, new_inode);
        if (!test_opt(new_dir->i_sb, NO_AUTO_DA_ALLOC))
            force_da_alloc = 1;
    }
    retval = 0;

end_rename:
    brelse(dir_bh);
    brelse(old_bh);
    brelse(new_bh);
    ext4_journal_stop(handle);
    if (retval == 0 && force_da_alloc)
        ext4_alloc_da_blocks(old_inode);
    return retval;
}

/*
 * directories can handle most operations...
 */
const struct inode_operations ext4_dir_inode_operations = {
    .create     = ext4_create,
    .lookup     = ext4_lookup,
    .link       = ext4_link,
    .unlink     = ext4_unlink,
    .symlink    = ext4_symlink,
    .mkdir      = ext4_mkdir,
    .rmdir      = ext4_rmdir,
    .mknod      = ext4_mknod,
    .rename     = ext4_rename,
    .setattr    = ext4_setattr,
#ifdef CONFIG_EXT4_FS_XATTR
    .setxattr   = generic_setxattr,
    .getxattr   = generic_getxattr,
    .listxattr  = ext4_listxattr,
    .removexattr    = generic_removexattr,
#endif
    .get_acl    = ext4_get_acl,
    .fiemap         = ext4_fiemap,
};

const struct inode_operations ext4_special_inode_operations = {
    .setattr    = ext4_setattr,
#ifdef CONFIG_EXT4_FS_XATTR
    .setxattr   = generic_setxattr,
    .getxattr   = generic_getxattr,
    .listxattr  = ext4_listxattr,
    .removexattr    = generic_removexattr,
#endif
    .get_acl    = ext4_get_acl,
};