ext4: Introduce ext4_lblk_t

[safe/jmp/linux-2.6] / fs / ext4 / namei.c

/*
 *  linux/fs/ext4/namei.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * 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 (davem@caip.rutgers.edu), 1995
 *  Directory entry file type support and forward compatibility hooks
 *      for B-tree directories by Theodore Ts'o (tytso@mit.edu), 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/ext4_fs.h>
#include <linux/ext4_jbd2.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 "namei.h"
#include "xattr.h"
#include "acl.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;

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

        if ((bh = ext4_bread(handle, inode, *block, 1, err))) {
                inode->i_size += inode->i_sb->s_blocksize;
                EXT4_I(inode)->i_disksize = inode->i_size;
                ext4_journal_get_write_access(handle,bh);
        }
        return bh;
}

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

#ifndef swap
#define swap(x, y) do { typeof(x) z = x; x = y; y = z; } while (0)
#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;
};

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(struct dentry *dentry,
                                 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, int size,
                        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);
static struct ext4_dir_entry_2* dx_pack_dirents (char *base, int size);
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 dentry *dentry,
                       struct ext4_dir_entry_2 **res_dir, int *err);
static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
                             struct inode *inode);

/*
 * 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;
        return 0? 20: 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);
        return 0? 22: 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("%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,
                                       ((char *) de - base));
                        }
                        space += EXT4_DIR_REC_LEN(de->name_len);
                        names++;
                }
                de = ext4_next_entry(de);
        }
        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("%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(struct dentry *dentry, 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 (dentry)
                dir = dentry->d_parent->d_inode;
        if (!(bh = ext4_bread (NULL,dir, 0, 0, err)))
                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, __FUNCTION__,
                             "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;
        hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
        if (dentry)
                ext4fs_dirhash(dentry->d_name.name, dentry->d_name.len, hinfo);
        hash = hinfo->hash;

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

        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, __FUNCTION__,
                             "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, __FUNCTION__,
                                     "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)))
                        goto fail2;
                at = entries = ((struct dx_node *) bh->b_data)->entries;
                if (dx_get_limit(entries) != dx_node_limit (dir)) {
                        ext4_warning(dir->i_sb, __FUNCTION__,
                                     "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, __FUNCTION__,
                             "Corrupt dir inode %ld, 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)))
                        return err; /* Failure */
                p++;
                brelse (p->bh);
                p->bh = bh;
                p->at = p->entries = ((struct dx_node *) bh->b_data)->entries;
        }
        return 1;
}


/*
 * 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)
{
        return (struct ext4_dir_entry_2 *)((char *)p +
                ext4_rec_len_from_disk(p->rec_len));
}

/*
 * 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, 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)))
                return err;

        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)) {
                if (!ext4_check_dir_entry("htree_dirblock_to_tree", dir, 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("In htree_fill_tree, start hash: %x:%x\n", start_hash,
                       start_minor_hash));
        dir = dir_file->f_path.dentry->d_inode;
        if (!(EXT4_I(dir)->i_flags & EXT4_INDEX_FL)) {
                hinfo.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
                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_file->f_path.dentry->d_inode, &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);
                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("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, int size,
                        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 + size)
        {
                if (de->name_len && de->inode) {
                        ext4fs_dirhash(de->name, de->name_len, &h);
                        map_tail--;
                        map_tail->hash = h.hash;
                        map_tail->offs = (u16) ((char *) de - base);
                        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);
        }
        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_I(inode)->i_flags &= ~EXT4_INDEX_FL;
}

/*
 * 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,
                                  struct dentry *dentry,
                                  unsigned long offset,
                                  struct ext4_dir_entry_2 ** res_dir)
{
        struct ext4_dir_entry_2 * de;
        char * dlimit;
        int de_len;
        const char *name = dentry->d_name.name;
        int namelen = dentry->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("ext4_find_entry",
                                                  dir, 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);
                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 dentry *dentry,
                                        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;
        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;
        struct inode *dir = dentry->d_parent->d_inode;
        int namelen;
        const u8 *name;
        unsigned blocksize;

        *res_dir = NULL;
        sb = dir->i_sb;
        blocksize = sb->s_blocksize;
        namelen = dentry->d_name.len;
        name = dentry->d_name.name;
        if (namelen > EXT4_NAME_LEN)
                return NULL;
        if (is_dx(dir)) {
                bh = ext4_dx_find_entry(dentry, 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("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_META, 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(sb, __FUNCTION__, "reading directory #%lu "
                                   "offset %lu", dir->i_ino,
                                   (unsigned long)block);
                        brelse(bh);
                        goto next;
                }
                i = search_dirblock(bh, dir, dentry,
                            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 dentry *dentry,
                       struct ext4_dir_entry_2 **res_dir, int *err)
{
        struct super_block * sb;
        struct dx_hash_info     hinfo;
        u32 hash;
        struct dx_frame frames[2], *frame;
        struct ext4_dir_entry_2 *de, *top;
        struct buffer_head *bh;
        ext4_lblk_t block;
        int retval;
        int namelen = dentry->d_name.len;
        const u8 *name = dentry->d_name.name;
        struct inode *dir = dentry->d_parent->d_inode;

        sb = dir->i_sb;
        /* NFS may look up ".." - look at dx_root directory block */
        if (namelen > 2 || name[0] != '.'||(name[1] != '.' && name[1] != '\0')){
                if (!(frame = dx_probe(dentry, NULL, &hinfo, frames, err)))
                        return NULL;
        } else {
                frame = frames;
                frame->bh = NULL;                       /* for dx_release() */
                frame->at = (struct dx_entry *)frames;  /* hack for zero entry*/
                dx_set_block(frame->at, 0);             /* dx_root block is 0 */
        }
        hash = hinfo.hash;
        do {
                block = dx_get_block(frame->at);
                if (!(bh = ext4_bread (NULL,dir, block, 0, err)))
                        goto errout;
                de = (struct ext4_dir_entry_2 *) bh->b_data;
                top = (struct ext4_dir_entry_2 *) ((char *) de + sb->s_blocksize -
                                       EXT4_DIR_REC_LEN(0));
                for (; de < top; de = ext4_next_entry(de))
                if (ext4_match (namelen, name, de)) {
                        if (!ext4_check_dir_entry("ext4_find_entry",
                                                  dir, de, bh,
                                  (block<<EXT4_BLOCK_SIZE_BITS(sb))
                                          +((char *)de - bh->b_data))) {
                                brelse (bh);
                                *err = ERR_BAD_DX_DIR;
                                goto errout;
                        }
                        *res_dir = de;
                        dx_release (frames);
                        return bh;
                }
                brelse (bh);
                /* Check to see if we should continue to search */
                retval = ext4_htree_next_block(dir, hash, frame,
                                               frames, NULL);
                if (retval < 0) {
                        ext4_warning(sb, __FUNCTION__,
                             "error reading index page in directory #%lu",
                             dir->i_ino);
                        *err = retval;
                        goto errout;
                }
        } while (retval == 1);

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

static struct dentry *ext4_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd)
{
        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(dentry, &de);
        inode = NULL;
        if (bh) {
                unsigned long ino = le32_to_cpu(de->inode);
                brelse (bh);
                if (!ext4_valid_inum(dir->i_sb, ino)) {
                        ext4_error(dir->i_sb, "ext4_lookup",
                                   "bad inode number: %lu", ino);
                        inode = NULL;
                } else
                        inode = iget(dir->i_sb, ino);

                if (!inode)
                        return ERR_PTR(-EACCES);

                if (is_bad_inode(inode)) {
                        iput(inode);
                        return ERR_PTR(-ENOENT);
                }
        }
        return d_splice_alias(inode, dentry);
}


struct dentry *ext4_get_parent(struct dentry *child)
{
        unsigned long ino;
        struct dentry *parent;
        struct inode *inode;
        struct dentry dotdot;
        struct ext4_dir_entry_2 * de;
        struct buffer_head *bh;

        dotdot.d_name.name = "..";
        dotdot.d_name.len = 2;
        dotdot.d_parent = child; /* confusing, isn't it! */

        bh = ext4_find_entry(&dotdot, &de);
        inode = NULL;
        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(child->d_inode->i_sb, "ext4_get_parent",
                           "bad inode number: %lu", ino);
                inode = NULL;
        } else
                inode = iget(child->d_inode->i_sb, ino);

        if (!inode)
                return ERR_PTR(-EACCES);

        if (is_bad_inode(inode)) {
                iput(inode);
                return ERR_PTR(-ENOENT);
        }

        parent = d_alloc_anon(inode);
        if (!parent) {
                iput(inode);
                parent = ERR_PTR(-ENOMEM);
        }
        return parent;
}

#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 rec_len = 0;

        while (count--) {
                struct ext4_dir_entry_2 *de = (struct ext4_dir_entry_2 *) (from + map->offs);
                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);
                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, int size)
{
        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 + size) {
                next = ext4_next_entry(de);
                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);
                        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, i;
        struct ext4_dir_entry_2 *de = NULL, *de2;
        int     err = 0;

        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);
        de = dx_pack_dirents(data1,blocksize);
        de->rec_len = ext4_rec_len_to_disk(data1 + blocksize - (char *) de);
        de2->rec_len = ext4_rec_len_to_disk(data2 + blocksize - (char *) de2);
        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_journal_dirty_metadata (handle, bh2);
        if (err)
                goto journal_error;
        err = ext4_journal_dirty_metadata (handle, 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.
 *
 * NOTE!  bh is NOT released in the case where ENOSPC is returned.  In
 * all other cases bh is released.
 */
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 long   offset = 0;
        unsigned short  reclen;
        int             nlen, rlen, err;
        char            *top;

        reclen = EXT4_DIR_REC_LEN(namelen);
        if (!de) {
                de = (struct ext4_dir_entry_2 *)bh->b_data;
                top = bh->b_data + dir->i_sb->s_blocksize - reclen;
                while ((char *) de <= top) {
                        if (!ext4_check_dir_entry("ext4_add_entry", dir, de,
                                                  bh, offset)) {
                                brelse (bh);
                                return -EIO;
                        }
                        if (ext4_match (namelen, name, de)) {
                                brelse (bh);
                                return -EEXIST;
                        }
                        nlen = EXT4_DIR_REC_LEN(de->name_len);
                        rlen = ext4_rec_len_from_disk(de->rec_len);
                        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);
                brelse(bh);
                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);
        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);
                de->rec_len = ext4_rec_len_to_disk(nlen);
                de = de1;
        }
        de->file_type = EXT4_FT_UNKNOWN;
        if (inode) {
                de->inode = cpu_to_le32(inode->i_ino);
                ext4_set_de_type(dir->i_sb, de, inode->i_mode);
        } else
                de->inode = 0;
        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_journal_dirty_metadata");
        err = ext4_journal_dirty_metadata(handle, bh);
        if (err)
                ext4_std_error(dir->i_sb, err);
        brelse(bh);
        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;
        char            *data1, *top;
        unsigned        len;
        int             retval;
        unsigned        blocksize;
        struct dx_hash_info hinfo;
        ext4_lblk_t  block;
        struct fake_dirent *fde;

        blocksize =  dir->i_sb->s_blocksize;
        dxtrace(printk("Creating index\n"));
        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;

        bh2 = ext4_append (handle, dir, &block, &retval);
        if (!(bh2)) {
                brelse(bh);
                return retval;
        }
        EXT4_I(dir)->i_flags |= EXT4_INDEX_FL;
        data1 = bh2->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));
        len = ((char *) root) + blocksize - (char *) de;
        memcpy (data1, de, len);
        de = (struct ext4_dir_entry_2 *) data1;
        top = data1 + len;
        while ((char *)(de2 = ext4_next_entry(de)) < top)
                de = de2;
        de->rec_len = ext4_rec_len_to_disk(data1 + blocksize - (char *) de);
        /* 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));
        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;
        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;
        de = do_split(handle,dir, &bh, frame, &hinfo, &retval);
        dx_release (frames);
        if (!(de))
                return retval;

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

/*
 *      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;
        unsigned long offset;
        struct buffer_head * bh;
        struct ext4_dir_entry_2 *de;
        struct super_block * sb;
        int     retval;
        int     dx_fallback=0;
        unsigned blocksize;
        ext4_lblk_t block, blocks;

        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_I(dir)->i_flags &= ~EXT4_INDEX_FL;
                dx_fallback++;
                ext4_mark_inode_dirty(handle, dir);
        }
        blocks = dir->i_size >> sb->s_blocksize_bits;
        for (block = 0, offset = 0; block < blocks; block++) {
                bh = ext4_bread(handle, dir, block, 0, &retval);
                if(!bh)
                        return retval;
                retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
                if (retval != -ENOSPC)
                        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);
        return add_dirent_to_buf(handle, dentry, inode, de, bh);
}

/*
 * 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, NULL, &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)))
                goto cleanup;

        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) {
                bh = NULL;
                goto cleanup;
        }

        /* Block full, should compress but for now just split */
        dxtrace(printk("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, __FUNCTION__,
                                     "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;
                node2->fake.rec_len = ext4_rec_len_to_disk(sb->s_blocksize);
                node2->fake.inode = 0;
                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("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_journal_dirty_metadata(handle, bh2);
                        if (err)
                                goto journal_error;
                        brelse (bh2);
                } else {
                        dxtrace(printk("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;
                }
                ext4_journal_dirty_metadata(handle, frames[0].bh);
        }
        de = do_split(handle, dir, &bh, frame, &hinfo, &err);
        if (!de)
                goto cleanup;
        err = add_dirent_to_buf(handle, dentry, inode, de, bh);
        bh = NULL;
        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;
        int i;

        i = 0;
        pde = NULL;
        de = (struct ext4_dir_entry_2 *) bh->b_data;
        while (i < bh->b_size) {
                if (!ext4_check_dir_entry("ext4_delete_entry", dir, de, bh, i))
                        return -EIO;
                if (de == de_del)  {
                        BUFFER_TRACE(bh, "get_write_access");
                        ext4_journal_get_write_access(handle, bh);
                        if (pde)
                                pde->rec_len = ext4_rec_len_to_disk(
                                        ext4_rec_len_from_disk(pde->rec_len) +
                                        ext4_rec_len_from_disk(de->rec_len));
                        else
                                de->inode = 0;
                        dir->i_version++;
                        BUFFER_TRACE(bh, "call ext4_journal_dirty_metadata");
                        ext4_journal_dirty_metadata(handle, bh);
                        return 0;
                }
                i += ext4_rec_len_from_disk(de->rec_len);
                pde = de;
                de = ext4_next_entry(de);
        }
        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) {
                        inode->i_nlink = 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)
{
        drop_nlink(inode);
        if (S_ISDIR(inode->i_mode) && inode->i_nlink == 0)
                inc_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);
                d_instantiate(dentry, inode);
                return 0;
        }
        drop_nlink(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, int mode,
                struct nameidata *nd)
{
        handle_t *handle;
        struct inode * inode;
        int err, retries = 0;

retry:
        handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                                        EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                                        2*EXT4_QUOTA_INIT_BLOCKS(dir->i_sb));
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (IS_DIRSYNC(dir))
                handle->h_sync = 1;

        inode = ext4_new_inode (handle, dir, mode);
        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,
                        int mode, dev_t rdev)
{
        handle_t *handle;
        struct inode *inode;
        int err, retries = 0;

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

retry:
        handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                                        EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                                        2*EXT4_QUOTA_INIT_BLOCKS(dir->i_sb));
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (IS_DIRSYNC(dir))
                handle->h_sync = 1;

        inode = ext4_new_inode (handle, dir, mode);
        err = PTR_ERR(inode);
        if (!IS_ERR(inode)) {
                init_special_inode(inode, inode->i_mode, rdev);
#ifdef CONFIG_EXT4DEV_FS_XATTR
                inode->i_op = &ext4_special_inode_operations;
#endif
                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, int mode)
{
        handle_t *handle;
        struct inode * inode;
        struct buffer_head * dir_block;
        struct ext4_dir_entry_2 * de;
        int err, retries = 0;

        if (EXT4_DIR_LINK_MAX(dir))
                return -EMLINK;

retry:
        handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                                        EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3 +
                                        2*EXT4_QUOTA_INIT_BLOCKS(dir->i_sb));
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (IS_DIRSYNC(dir))
                handle->h_sync = 1;

        inode = ext4_new_inode (handle, dir, S_IFDIR | mode);
        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;
        dir_block = ext4_bread (handle, inode, 0, 1, &err);
        if (!dir_block) {
                ext4_dec_count(handle, inode); /* is this nlink == 0? */
                ext4_mark_inode_dirty(handle, inode);
                iput (inode);
                goto out_stop;
        }
        BUFFER_TRACE(dir_block, "get_write_access");
        ext4_journal_get_write_access(handle, dir_block);
        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));
        strcpy (de->name, ".");
        ext4_set_de_type(dir->i_sb, de, S_IFDIR);
        de = ext4_next_entry(de);
        de->inode = cpu_to_le32(dir->i_ino);
        de->rec_len = ext4_rec_len_to_disk(inode->i_sb->s_blocksize -
                                                EXT4_DIR_REC_LEN(1));
        de->name_len = 2;
        strcpy (de->name, "..");
        ext4_set_de_type(dir->i_sb, de, S_IFDIR);
        inode->i_nlink = 2;
        BUFFER_TRACE(dir_block, "call ext4_journal_dirty_metadata");
        ext4_journal_dirty_metadata(handle, dir_block);
        brelse (dir_block);
        ext4_mark_inode_dirty(handle, inode);
        err = ext4_add_entry (handle, dentry, inode);
        if (err) {
                inode->i_nlink = 0;
                ext4_mark_inode_dirty(handle, inode);
                iput (inode);
                goto out_stop;
        }
        ext4_inc_count(handle, dir);
        ext4_update_dx_flag(dir);
        ext4_mark_inode_dirty(handle, dir);
        d_instantiate(dentry, inode);
out_stop:
        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 long 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->i_sb, __FUNCTION__,
                                   "error %d reading directory #%lu offset 0",
                                   err, inode->i_ino);
                else
                        ext4_warning(inode->i_sb, __FUNCTION__,
                                     "bad directory (dir #%lu) - no data block",
                                     inode->i_ino);
                return 1;
        }
        de = (struct ext4_dir_entry_2 *) bh->b_data;
        de1 = ext4_next_entry(de);
        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, "empty_dir",
                              "bad directory (dir #%lu) - no `.' or `..'",
                              inode->i_ino);
                brelse (bh);
                return 1;
        }
        offset = ext4_rec_len_from_disk(de->rec_len) +
                 ext4_rec_len_from_disk(de1->rec_len);
        de = ext4_next_entry(de1);
        while (offset < inode->i_size ) {
                if (!bh ||
                        (void *) de >= (void *) (bh->b_data+sb->s_blocksize)) {
                        err = 0;
                        brelse (bh);
                        bh = ext4_bread (NULL, inode,
                                offset >> EXT4_BLOCK_SIZE_BITS(sb), 0, &err);
                        if (!bh) {
                                if (err)
                                        ext4_error(sb, __FUNCTION__,
                                                   "error %d reading directory"
                                                   " #%lu offset %lu",
                                                   err, inode->i_ino, offset);
                                offset += sb->s_blocksize;
                                continue;
                        }
                        de = (struct ext4_dir_entry_2 *) bh->b_data;
                }
                if (!ext4_check_dir_entry("empty_dir", inode, 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);
                de = ext4_next_entry(de);
        }
        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;

        lock_super(sb);
        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. */

        /* @@@ FIXME: Observation from aviro:
         * I think I can trigger J_ASSERT in ext4_orphan_add().  We block
         * here (on lock_super()), so race with ext4_link() which might bump
         * ->i_nlink. For, say it, character device. Not a regular file,
         * not a directory, not a symlink and ->i_nlink > 0.
         */
        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;

        /* 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_journal_dirty_metadata(handle, EXT4_SB(sb)->s_sbh);
        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. */
        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:
        unlock_super(sb);
        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;
        unsigned long ino_next;
        struct ext4_iloc iloc;
        int err = 0;

        lock_super(inode->i_sb);
        if (list_empty(&ei->i_orphan)) {
                unlock_super(inode->i_sb);
                return 0;
        }

        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 %lu\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_journal_dirty_metadata(handle, sbi->s_sbh);
        } 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 %lu\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:
        unlock_super(inode->i_sb);
        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_INIT(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 (dentry, &de);
        if (!bh)
                goto end_rmdir;

        if (IS_DIRSYNC(dir))
                handle->h_sync = 1;

        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, "ext4_rmdir",
                              "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;

        /* Initialize quotas before so that eventual writes go
         * in separate transaction */
        DQUOT_INIT(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))
                handle->h_sync = 1;

        retval = -ENOENT;
        bh = ext4_find_entry (dentry, &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, "ext4_unlink",
                              "Deleting nonexistent file (%lu), %d",
                              inode->i_ino, inode->i_nlink);
                inode->i_nlink = 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);
        ext4_dec_count(handle, 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);
        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;

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

retry:
        handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                                        EXT4_INDEX_EXTRA_TRANS_BLOCKS + 5 +
                                        2*EXT4_QUOTA_INIT_BLOCKS(dir->i_sb));
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (IS_DIRSYNC(dir))
                handle->h_sync = 1;

        inode = ext4_new_inode (handle, dir, S_IFLNK|S_IRWXUGO);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_stop;

        if (l > sizeof (EXT4_I(inode)->i_data)) {
                inode->i_op = &ext4_symlink_inode_operations;
                ext4_set_aops(inode);
                /*
                 * page_symlink() calls into ext4_prepare/commit_write.
                 * We have a transaction open.  All is sweetness.  It also sets
                 * i_size in generic_commit_write().
                 */
                err = __page_symlink(inode, symname, l,
                                mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
                if (err) {
                        ext4_dec_count(handle, inode);
                        ext4_mark_inode_dirty(handle, inode);
                        iput (inode);
                        goto out_stop;
                }
        } else {
                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;
}

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 (EXT4_DIR_LINK_MAX(inode))
                return -EMLINK;

        /*
         * Return -ENOENT if we've raced with unlink and i_nlink is 0.  Doing
         * otherwise has the potential to corrupt the orphan inode list.
         */
        if (inode->i_nlink == 0)
                return -ENOENT;

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))
                handle->h_sync = 1;

        inode->i_ctime = ext4_current_time(inode);
        ext4_inc_count(handle, inode);
        atomic_inc(&inode->i_count);

        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;
}

#define PARENT_INO(buffer) \
        (ext4_next_entry((struct ext4_dir_entry_2 *)(buffer))->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;

        old_bh = new_bh = dir_bh = NULL;

        /* Initialize quotas before so that eventual writes go
         * in separate transaction */
        if (new_dentry->d_inode)
                DQUOT_INIT(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))
                handle->h_sync = 1;

        old_bh = ext4_find_entry (old_dentry, &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_dentry, &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;
                dir_bh = ext4_bread (handle, old_inode, 0, 0, &retval);
                if (!dir_bh)
                        goto end_rename;
                if (le32_to_cpu(PARENT_INO(dir_bh->b_data)) != old_dir->i_ino)
                        goto end_rename;
                retval = -EMLINK;
                if (!new_inode && new_dir!=old_dir &&
                                new_dir->i_nlink >= EXT4_LINK_MAX)
                        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");
                ext4_journal_get_write_access(handle, new_bh);
                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++;
                BUFFER_TRACE(new_bh, "call ext4_journal_dirty_metadata");
                ext4_journal_dirty_metadata(handle, new_bh);
                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_dentry, &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, "ext4_rename",
                                "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) {
                BUFFER_TRACE(dir_bh, "get_write_access");
                ext4_journal_get_write_access(handle, dir_bh);
                PARENT_INO(dir_bh->b_data) = cpu_to_le32(new_dir->i_ino);
                BUFFER_TRACE(dir_bh, "call ext4_journal_dirty_metadata");
                ext4_journal_dirty_metadata(handle, dir_bh);
                ext4_dec_count(handle, old_dir);
                if (new_inode) {
                        /* checked empty_dir above, can't have another parent,
                         * ext3_dec_count() won't work for many-linked dirs */
                        new_inode->i_nlink = 0;
                } 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);
        }
        retval = 0;

end_rename:
        brelse (dir_bh);
        brelse (old_bh);
        brelse (new_bh);
        ext4_journal_stop(handle);
        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_EXT4DEV_FS_XATTR
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext4_listxattr,
        .removexattr    = generic_removexattr,
#endif
        .permission     = ext4_permission,
};

const struct inode_operations ext4_special_inode_operations = {
        .setattr        = ext4_setattr,
#ifdef CONFIG_EXT4DEV_FS_XATTR
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext4_listxattr,
        .removexattr    = generic_removexattr,
#endif
        .permission     = ext4_permission,
};