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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,
                              u32 *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 unsigned dx_get_block (struct dx_entry *entry);
static void dx_set_block (struct dx_entry *entry, unsigned 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, u32 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 unsigned dx_get_block (struct dx_entry *entry)
{
      return le32_to_cpu(entry->block) & 0x00ffffff;
}

static inline void dx_set_block (struct dx_entry *entry, unsigned 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->%u ", i? dx_get_hash(entries + i) :
                        0, 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 = (struct ext4_dir_entry_2 *) ((char *) de + le16_to_cpu(de->rec_len));
      }
      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++)
      {
            u32 block = dx_get_block(entries), 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 + le16_to_cpu(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, int 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("In htree dirblock_to_tree: block %d\n", 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;
      int block, err;
      int count = 0;
      int ret;
      __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 = (struct ext4_dir_entry_2 *) ((char *) de + le16_to_cpu(de->rec_len));
      }
      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, u32 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 = le16_to_cpu(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;
      unsigned long 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;
      int nblocks, 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, 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;
      unsigned long 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 =
                        cpu_to_le16(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 = (struct ext4_dir_entry_2 *) ((char *) de +
                                        le16_to_cpu(de->rec_len));
            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 = cpu_to_le16(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;
      u32 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("Split block %i at %x, %i/%i\n",
            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 = cpu_to_le16(data1 + blocksize - (char *) de);
      de2->rec_len = cpu_to_le16(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 = le16_to_cpu(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 = le16_to_cpu(de->rec_len);
      if (de->inode) {
            struct ext4_dir_entry_2 *de1 = (struct ext4_dir_entry_2 *)((char *)de + nlen);
            de1->rec_len = cpu_to_le16(rlen - nlen);
            de->rec_len = cpu_to_le16(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;
      u32         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 + le16_to_cpu(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=(void*)de+le16_to_cpu(de->rec_len)) < top)
            de = de2;
      de->rec_len = cpu_to_le16(data1 + blocksize - (char *) de);
      /* Initialize the root; the dot dirents already exist */
      de = (struct ext4_dir_entry_2 *) (&root->dotdot);
      de->rec_len = cpu_to_le16(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;
      u32 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 = cpu_to_le16(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)) {
            u32 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 = cpu_to_le16(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 =
                              cpu_to_le16(le16_to_cpu(pde->rec_len) +
                                        le16_to_cpu(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 += le16_to_cpu(de->rec_len);
            pde = de;
            de = (struct ext4_dir_entry_2 *)
                  ((char *) de + le16_to_cpu(de->rec_len));
      }
      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 = cpu_to_le16(EXT4_DIR_REC_LEN(de->name_len));
      strcpy (de->name, ".");
      ext4_set_de_type(dir->i_sb, de, S_IFDIR);
      de = (struct ext4_dir_entry_2 *)
                  ((char *) de + le16_to_cpu(de->rec_len));
      de->inode = cpu_to_le32(dir->i_ino);
      de->rec_len = cpu_to_le16(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 = (struct ext4_dir_entry_2 *)
                  ((char *) de + le16_to_cpu(de->rec_len));
      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 = le16_to_cpu(de->rec_len) + le16_to_cpu(de1->rec_len);
      de = (struct ext4_dir_entry_2 *)
                  ((char *) de1 + le16_to_cpu(de1->rec_len));
      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 += le16_to_cpu(de->rec_len);
            de = (struct ext4_dir_entry_2 *)
                        ((char *) de + le16_to_cpu(de->rec_len));
      }
      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) \
      ((struct ext4_dir_entry_2 *) ((char *) buffer + \
      le16_to_cpu(((struct ext4_dir_entry_2 *) buffer)->rec_len)))->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,
};

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