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xattr.c

/*
 * linux/fs/ext4/xattr.c
 *
 * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
 *
 * Fix by Harrison Xing <harrison@mountainviewdata.com>.
 * Ext4 code with a lot of help from Eric Jarman <ejarman@acm.org>.
 * Extended attributes for symlinks and special files added per
 *  suggestion of Luka Renko <luka.renko@hermes.si>.
 * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
 *  Red Hat Inc.
 * ea-in-inode support by Alex Tomas <alex@clusterfs.com> aka bzzz
 *  and Andreas Gruenbacher <agruen@suse.de>.
 */

/*
 * Extended attributes are stored directly in inodes (on file systems with
 * inodes bigger than 128 bytes) and on additional disk blocks. The i_file_acl
 * field contains the block number if an inode uses an additional block. All
 * attributes must fit in the inode and one additional block. Blocks that
 * contain the identical set of attributes may be shared among several inodes.
 * Identical blocks are detected by keeping a cache of blocks that have
 * recently been accessed.
 *
 * The attributes in inodes and on blocks have a different header; the entries
 * are stored in the same format:
 *
 *   +------------------+
 *   | header           |
 *   | entry 1          | |
 *   | entry 2          | | growing downwards
 *   | entry 3          | v
 *   | four null bytes  |
 *   | . . .            |
 *   | value 1          | ^
 *   | value 3          | | growing upwards
 *   | value 2          | |
 *   +------------------+
 *
 * The header is followed by multiple entry descriptors. In disk blocks, the
 * entry descriptors are kept sorted. In inodes, they are unsorted. The
 * attribute values are aligned to the end of the block in no specific order.
 *
 * Locking strategy
 * ----------------
 * EXT4_I(inode)->i_file_acl is protected by EXT4_I(inode)->xattr_sem.
 * EA blocks are only changed if they are exclusive to an inode, so
 * holding xattr_sem also means that nothing but the EA block's reference
 * count can change. Multiple writers to the same block are synchronized
 * by the buffer lock.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/ext4_jbd2.h>
#include <linux/ext4_fs.h>
#include <linux/mbcache.h>
#include <linux/quotaops.h>
#include <linux/rwsem.h>
#include "xattr.h"
#include "acl.h"

#define BHDR(bh) ((struct ext4_xattr_header *)((bh)->b_data))
#define ENTRY(ptr) ((struct ext4_xattr_entry *)(ptr))
#define BFIRST(bh) ENTRY(BHDR(bh)+1)
#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)

#ifdef EXT4_XATTR_DEBUG
# define ea_idebug(inode, f...) do { \
            printk(KERN_DEBUG "inode %s:%lu: ", \
                  inode->i_sb->s_id, inode->i_ino); \
            printk(f); \
            printk("\n"); \
      } while (0)
# define ea_bdebug(bh, f...) do { \
            char b[BDEVNAME_SIZE]; \
            printk(KERN_DEBUG "block %s:%lu: ", \
                  bdevname(bh->b_bdev, b), \
                  (unsigned long) bh->b_blocknr); \
            printk(f); \
            printk("\n"); \
      } while (0)
#else
# define ea_idebug(f...)
# define ea_bdebug(f...)
#endif

static void ext4_xattr_cache_insert(struct buffer_head *);
static struct buffer_head *ext4_xattr_cache_find(struct inode *,
                                     struct ext4_xattr_header *,
                                     struct mb_cache_entry **);
static void ext4_xattr_rehash(struct ext4_xattr_header *,
                        struct ext4_xattr_entry *);

static struct mb_cache *ext4_xattr_cache;

static struct xattr_handler *ext4_xattr_handler_map[] = {
      [EXT4_XATTR_INDEX_USER]            = &ext4_xattr_user_handler,
#ifdef CONFIG_EXT4DEV_FS_POSIX_ACL
      [EXT4_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext4_xattr_acl_access_handler,
      [EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext4_xattr_acl_default_handler,
#endif
      [EXT4_XATTR_INDEX_TRUSTED]         = &ext4_xattr_trusted_handler,
#ifdef CONFIG_EXT4DEV_FS_SECURITY
      [EXT4_XATTR_INDEX_SECURITY]        = &ext4_xattr_security_handler,
#endif
};

struct xattr_handler *ext4_xattr_handlers[] = {
      &ext4_xattr_user_handler,
      &ext4_xattr_trusted_handler,
#ifdef CONFIG_EXT4DEV_FS_POSIX_ACL
      &ext4_xattr_acl_access_handler,
      &ext4_xattr_acl_default_handler,
#endif
#ifdef CONFIG_EXT4DEV_FS_SECURITY
      &ext4_xattr_security_handler,
#endif
      NULL
};

static inline struct xattr_handler *
ext4_xattr_handler(int name_index)
{
      struct xattr_handler *handler = NULL;

      if (name_index > 0 && name_index < ARRAY_SIZE(ext4_xattr_handler_map))
            handler = ext4_xattr_handler_map[name_index];
      return handler;
}

/*
 * Inode operation listxattr()
 *
 * dentry->d_inode->i_mutex: don't care
 */
ssize_t
ext4_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
      return ext4_xattr_list(dentry->d_inode, buffer, size);
}

static int
ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end)
{
      while (!IS_LAST_ENTRY(entry)) {
            struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
            if ((void *)next >= end)
                  return -EIO;
            entry = next;
      }
      return 0;
}

static inline int
ext4_xattr_check_block(struct buffer_head *bh)
{
      int error;

      if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
          BHDR(bh)->h_blocks != cpu_to_le32(1))
            return -EIO;
      error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
      return error;
}

static inline int
ext4_xattr_check_entry(struct ext4_xattr_entry *entry, size_t size)
{
      size_t value_size = le32_to_cpu(entry->e_value_size);

      if (entry->e_value_block != 0 || value_size > size ||
          le16_to_cpu(entry->e_value_offs) + value_size > size)
            return -EIO;
      return 0;
}

static int
ext4_xattr_find_entry(struct ext4_xattr_entry **pentry, int name_index,
                  const char *name, size_t size, int sorted)
{
      struct ext4_xattr_entry *entry;
      size_t name_len;
      int cmp = 1;

      if (name == NULL)
            return -EINVAL;
      name_len = strlen(name);
      entry = *pentry;
      for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
            cmp = name_index - entry->e_name_index;
            if (!cmp)
                  cmp = name_len - entry->e_name_len;
            if (!cmp)
                  cmp = memcmp(name, entry->e_name, name_len);
            if (cmp <= 0 && (sorted || cmp == 0))
                  break;
      }
      *pentry = entry;
      if (!cmp && ext4_xattr_check_entry(entry, size))
                  return -EIO;
      return cmp ? -ENODATA : 0;
}

static int
ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
                 void *buffer, size_t buffer_size)
{
      struct buffer_head *bh = NULL;
      struct ext4_xattr_entry *entry;
      size_t size;
      int error;

      ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
              name_index, name, buffer, (long)buffer_size);

      error = -ENODATA;
      if (!EXT4_I(inode)->i_file_acl)
            goto cleanup;
      ea_idebug(inode, "reading block %u", EXT4_I(inode)->i_file_acl);
      bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
      if (!bh)
            goto cleanup;
      ea_bdebug(bh, "b_count=%d, refcount=%d",
            atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
      if (ext4_xattr_check_block(bh)) {
bad_block:  ext4_error(inode->i_sb, __FUNCTION__,
                     "inode %lu: bad block %llu", inode->i_ino,
                     EXT4_I(inode)->i_file_acl);
            error = -EIO;
            goto cleanup;
      }
      ext4_xattr_cache_insert(bh);
      entry = BFIRST(bh);
      error = ext4_xattr_find_entry(&entry, name_index, name, bh->b_size, 1);
      if (error == -EIO)
            goto bad_block;
      if (error)
            goto cleanup;
      size = le32_to_cpu(entry->e_value_size);
      if (buffer) {
            error = -ERANGE;
            if (size > buffer_size)
                  goto cleanup;
            memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
                   size);
      }
      error = size;

cleanup:
      brelse(bh);
      return error;
}

static int
ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
                 void *buffer, size_t buffer_size)
{
      struct ext4_xattr_ibody_header *header;
      struct ext4_xattr_entry *entry;
      struct ext4_inode *raw_inode;
      struct ext4_iloc iloc;
      size_t size;
      void *end;
      int error;

      if (!(EXT4_I(inode)->i_state & EXT4_STATE_XATTR))
            return -ENODATA;
      error = ext4_get_inode_loc(inode, &iloc);
      if (error)
            return error;
      raw_inode = ext4_raw_inode(&iloc);
      header = IHDR(inode, raw_inode);
      entry = IFIRST(header);
      end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
      error = ext4_xattr_check_names(entry, end);
      if (error)
            goto cleanup;
      error = ext4_xattr_find_entry(&entry, name_index, name,
                              end - (void *)entry, 0);
      if (error)
            goto cleanup;
      size = le32_to_cpu(entry->e_value_size);
      if (buffer) {
            error = -ERANGE;
            if (size > buffer_size)
                  goto cleanup;
            memcpy(buffer, (void *)IFIRST(header) +
                   le16_to_cpu(entry->e_value_offs), size);
      }
      error = size;

cleanup:
      brelse(iloc.bh);
      return error;
}

/*
 * ext4_xattr_get()
 *
 * Copy an extended attribute into the buffer
 * provided, or compute the buffer size required.
 * Buffer is NULL to compute the size of the buffer required.
 *
 * Returns a negative error number on failure, or the number of bytes
 * used / required on success.
 */
int
ext4_xattr_get(struct inode *inode, int name_index, const char *name,
             void *buffer, size_t buffer_size)
{
      int error;

      down_read(&EXT4_I(inode)->xattr_sem);
      error = ext4_xattr_ibody_get(inode, name_index, name, buffer,
                             buffer_size);
      if (error == -ENODATA)
            error = ext4_xattr_block_get(inode, name_index, name, buffer,
                                   buffer_size);
      up_read(&EXT4_I(inode)->xattr_sem);
      return error;
}

static int
ext4_xattr_list_entries(struct inode *inode, struct ext4_xattr_entry *entry,
                  char *buffer, size_t buffer_size)
{
      size_t rest = buffer_size;

      for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
            struct xattr_handler *handler =
                  ext4_xattr_handler(entry->e_name_index);

            if (handler) {
                  size_t size = handler->list(inode, buffer, rest,
                                        entry->e_name,
                                        entry->e_name_len);
                  if (buffer) {
                        if (size > rest)
                              return -ERANGE;
                        buffer += size;
                  }
                  rest -= size;
            }
      }
      return buffer_size - rest;
}

static int
ext4_xattr_block_list(struct inode *inode, char *buffer, size_t buffer_size)
{
      struct buffer_head *bh = NULL;
      int error;

      ea_idebug(inode, "buffer=%p, buffer_size=%ld",
              buffer, (long)buffer_size);

      error = 0;
      if (!EXT4_I(inode)->i_file_acl)
            goto cleanup;
      ea_idebug(inode, "reading block %u", EXT4_I(inode)->i_file_acl);
      bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
      error = -EIO;
      if (!bh)
            goto cleanup;
      ea_bdebug(bh, "b_count=%d, refcount=%d",
            atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
      if (ext4_xattr_check_block(bh)) {
            ext4_error(inode->i_sb, __FUNCTION__,
                     "inode %lu: bad block %llu", inode->i_ino,
                     EXT4_I(inode)->i_file_acl);
            error = -EIO;
            goto cleanup;
      }
      ext4_xattr_cache_insert(bh);
      error = ext4_xattr_list_entries(inode, BFIRST(bh), buffer, buffer_size);

cleanup:
      brelse(bh);

      return error;
}

static int
ext4_xattr_ibody_list(struct inode *inode, char *buffer, size_t buffer_size)
{
      struct ext4_xattr_ibody_header *header;
      struct ext4_inode *raw_inode;
      struct ext4_iloc iloc;
      void *end;
      int error;

      if (!(EXT4_I(inode)->i_state & EXT4_STATE_XATTR))
            return 0;
      error = ext4_get_inode_loc(inode, &iloc);
      if (error)
            return error;
      raw_inode = ext4_raw_inode(&iloc);
      header = IHDR(inode, raw_inode);
      end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
      error = ext4_xattr_check_names(IFIRST(header), end);
      if (error)
            goto cleanup;
      error = ext4_xattr_list_entries(inode, IFIRST(header),
                              buffer, buffer_size);

cleanup:
      brelse(iloc.bh);
      return error;
}

/*
 * ext4_xattr_list()
 *
 * Copy a list of attribute names into the buffer
 * provided, or compute the buffer size required.
 * Buffer is NULL to compute the size of the buffer required.
 *
 * Returns a negative error number on failure, or the number of bytes
 * used / required on success.
 */
int
ext4_xattr_list(struct inode *inode, char *buffer, size_t buffer_size)
{
      int i_error, b_error;

      down_read(&EXT4_I(inode)->xattr_sem);
      i_error = ext4_xattr_ibody_list(inode, buffer, buffer_size);
      if (i_error < 0) {
            b_error = 0;
      } else {
            if (buffer) {
                  buffer += i_error;
                  buffer_size -= i_error;
            }
            b_error = ext4_xattr_block_list(inode, buffer, buffer_size);
            if (b_error < 0)
                  i_error = 0;
      }
      up_read(&EXT4_I(inode)->xattr_sem);
      return i_error + b_error;
}

/*
 * If the EXT4_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 * not set, set it.
 */
static void ext4_xattr_update_super_block(handle_t *handle,
                                struct super_block *sb)
{
      if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_EXT_ATTR))
            return;

      if (ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh) == 0) {
            EXT4_SET_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_EXT_ATTR);
            sb->s_dirt = 1;
            ext4_journal_dirty_metadata(handle, EXT4_SB(sb)->s_sbh);
      }
}

/*
 * Release the xattr block BH: If the reference count is > 1, decrement
 * it; otherwise free the block.
 */
static void
ext4_xattr_release_block(handle_t *handle, struct inode *inode,
                   struct buffer_head *bh)
{
      struct mb_cache_entry *ce = NULL;
      int error = 0;

      ce = mb_cache_entry_get(ext4_xattr_cache, bh->b_bdev, bh->b_blocknr);
      error = ext4_journal_get_write_access(handle, bh);
      if (error)
            goto out;

      lock_buffer(bh);
      if (BHDR(bh)->h_refcount == cpu_to_le32(1)) {
            ea_bdebug(bh, "refcount now=0; freeing");
            if (ce)
                  mb_cache_entry_free(ce);
            ext4_free_blocks(handle, inode, bh->b_blocknr, 1);
            get_bh(bh);
            ext4_forget(handle, 1, inode, bh, bh->b_blocknr);
      } else {
            BHDR(bh)->h_refcount = cpu_to_le32(
                        le32_to_cpu(BHDR(bh)->h_refcount) - 1);
            error = ext4_journal_dirty_metadata(handle, bh);
            if (IS_SYNC(inode))
                  handle->h_sync = 1;
            DQUOT_FREE_BLOCK(inode, 1);
            ea_bdebug(bh, "refcount now=%d; releasing",
                    le32_to_cpu(BHDR(bh)->h_refcount));
            if (ce)
                  mb_cache_entry_release(ce);
      }
      unlock_buffer(bh);
out:
      ext4_std_error(inode->i_sb, error);
      return;
}

/*
 * Find the available free space for EAs. This also returns the total number of
 * bytes used by EA entries.
 */
static size_t ext4_xattr_free_space(struct ext4_xattr_entry *last,
                            size_t *min_offs, void *base, int *total)
{
      for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
            *total += EXT4_XATTR_LEN(last->e_name_len);
            if (!last->e_value_block && last->e_value_size) {
                  size_t offs = le16_to_cpu(last->e_value_offs);
                  if (offs < *min_offs)
                        *min_offs = offs;
            }
      }
      return (*min_offs - ((void *)last - base) - sizeof(__u32));
}

struct ext4_xattr_info {
      int name_index;
      const char *name;
      const void *value;
      size_t value_len;
};

struct ext4_xattr_search {
      struct ext4_xattr_entry *first;
      void *base;
      void *end;
      struct ext4_xattr_entry *here;
      int not_found;
};

static int
ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s)
{
      struct ext4_xattr_entry *last;
      size_t free, min_offs = s->end - s->base, name_len = strlen(i->name);

      /* Compute min_offs and last. */
      last = s->first;
      for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
            if (!last->e_value_block && last->e_value_size) {
                  size_t offs = le16_to_cpu(last->e_value_offs);
                  if (offs < min_offs)
                        min_offs = offs;
            }
      }
      free = min_offs - ((void *)last - s->base) - sizeof(__u32);
      if (!s->not_found) {
            if (!s->here->e_value_block && s->here->e_value_size) {
                  size_t size = le32_to_cpu(s->here->e_value_size);
                  free += EXT4_XATTR_SIZE(size);
            }
            free += EXT4_XATTR_LEN(name_len);
      }
      if (i->value) {
            if (free < EXT4_XATTR_SIZE(i->value_len) ||
                free < EXT4_XATTR_LEN(name_len) +
                     EXT4_XATTR_SIZE(i->value_len))
                  return -ENOSPC;
      }

      if (i->value && s->not_found) {
            /* Insert the new name. */
            size_t size = EXT4_XATTR_LEN(name_len);
            size_t rest = (void *)last - (void *)s->here + sizeof(__u32);
            memmove((void *)s->here + size, s->here, rest);
            memset(s->here, 0, size);
            s->here->e_name_index = i->name_index;
            s->here->e_name_len = name_len;
            memcpy(s->here->e_name, i->name, name_len);
      } else {
            if (!s->here->e_value_block && s->here->e_value_size) {
                  void *first_val = s->base + min_offs;
                  size_t offs = le16_to_cpu(s->here->e_value_offs);
                  void *val = s->base + offs;
                  size_t size = EXT4_XATTR_SIZE(
                        le32_to_cpu(s->here->e_value_size));

                  if (i->value && size == EXT4_XATTR_SIZE(i->value_len)) {
                        /* The old and the new value have the same
                           size. Just replace. */
                        s->here->e_value_size =
                              cpu_to_le32(i->value_len);
                        memset(val + size - EXT4_XATTR_PAD, 0,
                               EXT4_XATTR_PAD); /* Clear pad bytes. */
                        memcpy(val, i->value, i->value_len);
                        return 0;
                  }

                  /* Remove the old value. */
                  memmove(first_val + size, first_val, val - first_val);
                  memset(first_val, 0, size);
                  s->here->e_value_size = 0;
                  s->here->e_value_offs = 0;
                  min_offs += size;

                  /* Adjust all value offsets. */
                  last = s->first;
                  while (!IS_LAST_ENTRY(last)) {
                        size_t o = le16_to_cpu(last->e_value_offs);
                        if (!last->e_value_block &&
                            last->e_value_size && o < offs)
                              last->e_value_offs =
                                    cpu_to_le16(o + size);
                        last = EXT4_XATTR_NEXT(last);
                  }
            }
            if (!i->value) {
                  /* Remove the old name. */
                  size_t size = EXT4_XATTR_LEN(name_len);
                  last = ENTRY((void *)last - size);
                  memmove(s->here, (void *)s->here + size,
                        (void *)last - (void *)s->here + sizeof(__u32));
                  memset(last, 0, size);
            }
      }

      if (i->value) {
            /* Insert the new value. */
            s->here->e_value_size = cpu_to_le32(i->value_len);
            if (i->value_len) {
                  size_t size = EXT4_XATTR_SIZE(i->value_len);
                  void *val = s->base + min_offs - size;
                  s->here->e_value_offs = cpu_to_le16(min_offs - size);
                  memset(val + size - EXT4_XATTR_PAD, 0,
                         EXT4_XATTR_PAD); /* Clear the pad bytes. */
                  memcpy(val, i->value, i->value_len);
            }
      }
      return 0;
}

struct ext4_xattr_block_find {
      struct ext4_xattr_search s;
      struct buffer_head *bh;
};

static int
ext4_xattr_block_find(struct inode *inode, struct ext4_xattr_info *i,
                  struct ext4_xattr_block_find *bs)
{
      struct super_block *sb = inode->i_sb;
      int error;

      ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
              i->name_index, i->name, i->value, (long)i->value_len);

      if (EXT4_I(inode)->i_file_acl) {
            /* The inode already has an extended attribute block. */
            bs->bh = sb_bread(sb, EXT4_I(inode)->i_file_acl);
            error = -EIO;
            if (!bs->bh)
                  goto cleanup;
            ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
                  atomic_read(&(bs->bh->b_count)),
                  le32_to_cpu(BHDR(bs->bh)->h_refcount));
            if (ext4_xattr_check_block(bs->bh)) {
                  ext4_error(sb, __FUNCTION__,
                        "inode %lu: bad block %llu", inode->i_ino,
                        EXT4_I(inode)->i_file_acl);
                  error = -EIO;
                  goto cleanup;
            }
            /* Find the named attribute. */
            bs->s.base = BHDR(bs->bh);
            bs->s.first = BFIRST(bs->bh);
            bs->s.end = bs->bh->b_data + bs->bh->b_size;
            bs->s.here = bs->s.first;
            error = ext4_xattr_find_entry(&bs->s.here, i->name_index,
                                    i->name, bs->bh->b_size, 1);
            if (error && error != -ENODATA)
                  goto cleanup;
            bs->s.not_found = error;
      }
      error = 0;

cleanup:
      return error;
}

static int
ext4_xattr_block_set(handle_t *handle, struct inode *inode,
                 struct ext4_xattr_info *i,
                 struct ext4_xattr_block_find *bs)
{
      struct super_block *sb = inode->i_sb;
      struct buffer_head *new_bh = NULL;
      struct ext4_xattr_search *s = &bs->s;
      struct mb_cache_entry *ce = NULL;
      int error = 0;

#define header(x) ((struct ext4_xattr_header *)(x))

      if (i->value && i->value_len > sb->s_blocksize)
            return -ENOSPC;
      if (s->base) {
            ce = mb_cache_entry_get(ext4_xattr_cache, bs->bh->b_bdev,
                              bs->bh->b_blocknr);
            error = ext4_journal_get_write_access(handle, bs->bh);
            if (error)
                  goto cleanup;
            lock_buffer(bs->bh);

            if (header(s->base)->h_refcount == cpu_to_le32(1)) {
                  if (ce) {
                        mb_cache_entry_free(ce);
                        ce = NULL;
                  }
                  ea_bdebug(bs->bh, "modifying in-place");
                  error = ext4_xattr_set_entry(i, s);
                  if (!error) {
                        if (!IS_LAST_ENTRY(s->first))
                              ext4_xattr_rehash(header(s->base),
                                            s->here);
                        ext4_xattr_cache_insert(bs->bh);
                  }
                  unlock_buffer(bs->bh);
                  if (error == -EIO)
                        goto bad_block;
                  if (!error)
                        error = ext4_journal_dirty_metadata(handle,
                                                    bs->bh);
                  if (error)
                        goto cleanup;
                  goto inserted;
            } else {
                  int offset = (char *)s->here - bs->bh->b_data;

                  unlock_buffer(bs->bh);
                  jbd2_journal_release_buffer(handle, bs->bh);
                  if (ce) {
                        mb_cache_entry_release(ce);
                        ce = NULL;
                  }
                  ea_bdebug(bs->bh, "cloning");
                  s->base = kmalloc(bs->bh->b_size, GFP_KERNEL);
                  error = -ENOMEM;
                  if (s->base == NULL)
                        goto cleanup;
                  memcpy(s->base, BHDR(bs->bh), bs->bh->b_size);
                  s->first = ENTRY(header(s->base)+1);
                  header(s->base)->h_refcount = cpu_to_le32(1);
                  s->here = ENTRY(s->base + offset);
                  s->end = s->base + bs->bh->b_size;
            }
      } else {
            /* Allocate a buffer where we construct the new block. */
            s->base = kzalloc(sb->s_blocksize, GFP_KERNEL);
            /* assert(header == s->base) */
            error = -ENOMEM;
            if (s->base == NULL)
                  goto cleanup;
            header(s->base)->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
            header(s->base)->h_blocks = cpu_to_le32(1);
            header(s->base)->h_refcount = cpu_to_le32(1);
            s->first = ENTRY(header(s->base)+1);
            s->here = ENTRY(header(s->base)+1);
            s->end = s->base + sb->s_blocksize;
      }

      error = ext4_xattr_set_entry(i, s);
      if (error == -EIO)
            goto bad_block;
      if (error)
            goto cleanup;
      if (!IS_LAST_ENTRY(s->first))
            ext4_xattr_rehash(header(s->base), s->here);

inserted:
      if (!IS_LAST_ENTRY(s->first)) {
            new_bh = ext4_xattr_cache_find(inode, header(s->base), &ce);
            if (new_bh) {
                  /* We found an identical block in the cache. */
                  if (new_bh == bs->bh)
                        ea_bdebug(new_bh, "keeping");
                  else {
                        /* The old block is released after updating
                           the inode. */
                        error = -EDQUOT;
                        if (DQUOT_ALLOC_BLOCK(inode, 1))
                              goto cleanup;
                        error = ext4_journal_get_write_access(handle,
                                                      new_bh);
                        if (error)
                              goto cleanup_dquot;
                        lock_buffer(new_bh);
                        BHDR(new_bh)->h_refcount = cpu_to_le32(1 +
                              le32_to_cpu(BHDR(new_bh)->h_refcount));
                        ea_bdebug(new_bh, "reusing; refcount now=%d",
                              le32_to_cpu(BHDR(new_bh)->h_refcount));
                        unlock_buffer(new_bh);
                        error = ext4_journal_dirty_metadata(handle,
                                                    new_bh);
                        if (error)
                              goto cleanup_dquot;
                  }
                  mb_cache_entry_release(ce);
                  ce = NULL;
            } else if (bs->bh && s->base == bs->bh->b_data) {
                  /* We were modifying this block in-place. */
                  ea_bdebug(bs->bh, "keeping this block");
                  new_bh = bs->bh;
                  get_bh(new_bh);
            } else {
                  /* We need to allocate a new block */
                  ext4_fsblk_t goal = le32_to_cpu(
                              EXT4_SB(sb)->s_es->s_first_data_block) +
                        (ext4_fsblk_t)EXT4_I(inode)->i_block_group *
                        EXT4_BLOCKS_PER_GROUP(sb);
                  ext4_fsblk_t block = ext4_new_block(handle, inode,
                                          goal, &error);
                  if (error)
                        goto cleanup;
                  ea_idebug(inode, "creating block %d", block);

                  new_bh = sb_getblk(sb, block);
                  if (!new_bh) {
getblk_failed:
                        ext4_free_blocks(handle, inode, block, 1);
                        error = -EIO;
                        goto cleanup;
                  }
                  lock_buffer(new_bh);
                  error = ext4_journal_get_create_access(handle, new_bh);
                  if (error) {
                        unlock_buffer(new_bh);
                        goto getblk_failed;
                  }
                  memcpy(new_bh->b_data, s->base, new_bh->b_size);
                  set_buffer_uptodate(new_bh);
                  unlock_buffer(new_bh);
                  ext4_xattr_cache_insert(new_bh);
                  error = ext4_journal_dirty_metadata(handle, new_bh);
                  if (error)
                        goto cleanup;
            }
      }

      /* Update the inode. */
      EXT4_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;

      /* Drop the previous xattr block. */
      if (bs->bh && bs->bh != new_bh)
            ext4_xattr_release_block(handle, inode, bs->bh);
      error = 0;

cleanup:
      if (ce)
            mb_cache_entry_release(ce);
      brelse(new_bh);
      if (!(bs->bh && s->base == bs->bh->b_data))
            kfree(s->base);

      return error;

cleanup_dquot:
      DQUOT_FREE_BLOCK(inode, 1);
      goto cleanup;

bad_block:
      ext4_error(inode->i_sb, __FUNCTION__,
               "inode %lu: bad block %llu", inode->i_ino,
               EXT4_I(inode)->i_file_acl);
      goto cleanup;

#undef header
}

struct ext4_xattr_ibody_find {
      struct ext4_xattr_search s;
      struct ext4_iloc iloc;
};

static int
ext4_xattr_ibody_find(struct inode *inode, struct ext4_xattr_info *i,
                  struct ext4_xattr_ibody_find *is)
{
      struct ext4_xattr_ibody_header *header;
      struct ext4_inode *raw_inode;
      int error;

      if (EXT4_I(inode)->i_extra_isize == 0)
            return 0;
      raw_inode = ext4_raw_inode(&is->iloc);
      header = IHDR(inode, raw_inode);
      is->s.base = is->s.first = IFIRST(header);
      is->s.here = is->s.first;
      is->s.end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
      if (EXT4_I(inode)->i_state & EXT4_STATE_XATTR) {
            error = ext4_xattr_check_names(IFIRST(header), is->s.end);
            if (error)
                  return error;
            /* Find the named attribute. */
            error = ext4_xattr_find_entry(&is->s.here, i->name_index,
                                    i->name, is->s.end -
                                    (void *)is->s.base, 0);
            if (error && error != -ENODATA)
                  return error;
            is->s.not_found = error;
      }
      return 0;
}

static int
ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
                 struct ext4_xattr_info *i,
                 struct ext4_xattr_ibody_find *is)
{
      struct ext4_xattr_ibody_header *header;
      struct ext4_xattr_search *s = &is->s;
      int error;

      if (EXT4_I(inode)->i_extra_isize == 0)
            return -ENOSPC;
      error = ext4_xattr_set_entry(i, s);
      if (error)
            return error;
      header = IHDR(inode, ext4_raw_inode(&is->iloc));
      if (!IS_LAST_ENTRY(s->first)) {
            header->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
            EXT4_I(inode)->i_state |= EXT4_STATE_XATTR;
      } else {
            header->h_magic = cpu_to_le32(0);
            EXT4_I(inode)->i_state &= ~EXT4_STATE_XATTR;
      }
      return 0;
}

/*
 * ext4_xattr_set_handle()
 *
 * Create, replace or remove an extended attribute for this inode. Buffer
 * is NULL to remove an existing extended attribute, and non-NULL to
 * either replace an existing extended attribute, or create a new extended
 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 * specify that an extended attribute must exist and must not exist
 * previous to the call, respectively.
 *
 * Returns 0, or a negative error number on failure.
 */
int
ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
                  const char *name, const void *value, size_t value_len,
                  int flags)
{
      struct ext4_xattr_info i = {
            .name_index = name_index,
            .name = name,
            .value = value,
            .value_len = value_len,

      };
      struct ext4_xattr_ibody_find is = {
            .s = { .not_found = -ENODATA, },
      };
      struct ext4_xattr_block_find bs = {
            .s = { .not_found = -ENODATA, },
      };
      int error;

      if (!name)
            return -EINVAL;
      if (strlen(name) > 255)
            return -ERANGE;
      down_write(&EXT4_I(inode)->xattr_sem);
      error = ext4_get_inode_loc(inode, &is.iloc);
      if (error)
            goto cleanup;

      if (EXT4_I(inode)->i_state & EXT4_STATE_NEW) {
            struct ext4_inode *raw_inode = ext4_raw_inode(&is.iloc);
            memset(raw_inode, 0, EXT4_SB(inode->i_sb)->s_inode_size);
            EXT4_I(inode)->i_state &= ~EXT4_STATE_NEW;
      }

      error = ext4_xattr_ibody_find(inode, &i, &is);
      if (error)
            goto cleanup;
      if (is.s.not_found)
            error = ext4_xattr_block_find(inode, &i, &bs);
      if (error)
            goto cleanup;
      if (is.s.not_found && bs.s.not_found) {
            error = -ENODATA;
            if (flags & XATTR_REPLACE)
                  goto cleanup;
            error = 0;
            if (!value)
                  goto cleanup;
      } else {
            error = -EEXIST;
            if (flags & XATTR_CREATE)
                  goto cleanup;
      }
      error = ext4_journal_get_write_access(handle, is.iloc.bh);
      if (error)
            goto cleanup;
      if (!value) {
            if (!is.s.not_found)
                  error = ext4_xattr_ibody_set(handle, inode, &i, &is);
            else if (!bs.s.not_found)
                  error = ext4_xattr_block_set(handle, inode, &i, &bs);
      } else {
            error = ext4_xattr_ibody_set(handle, inode, &i, &is);
            if (!error && !bs.s.not_found) {
                  i.value = NULL;
                  error = ext4_xattr_block_set(handle, inode, &i, &bs);
            } else if (error == -ENOSPC) {
                  error = ext4_xattr_block_set(handle, inode, &i, &bs);
                  if (error)
                        goto cleanup;
                  if (!is.s.not_found) {
                        i.value = NULL;
                        error = ext4_xattr_ibody_set(handle, inode, &i,
                                               &is);
                  }
            }
      }
      if (!error) {
            ext4_xattr_update_super_block(handle, inode->i_sb);
            inode->i_ctime = ext4_current_time(inode);
            if (!value)
                  EXT4_I(inode)->i_state &= ~EXT4_STATE_NO_EXPAND;
            error = ext4_mark_iloc_dirty(handle, inode, &is.iloc);
            /*
             * The bh is consumed by ext4_mark_iloc_dirty, even with
             * error != 0.
             */
            is.iloc.bh = NULL;
            if (IS_SYNC(inode))
                  handle->h_sync = 1;
      }

cleanup:
      brelse(is.iloc.bh);
      brelse(bs.bh);
      up_write(&EXT4_I(inode)->xattr_sem);
      return error;
}

/*
 * ext4_xattr_set()
 *
 * Like ext4_xattr_set_handle, but start from an inode. This extended
 * attribute modification is a filesystem transaction by itself.
 *
 * Returns 0, or a negative error number on failure.
 */
int
ext4_xattr_set(struct inode *inode, int name_index, const char *name,
             const void *value, size_t value_len, int flags)
{
      handle_t *handle;
      int error, retries = 0;

retry:
      handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
      if (IS_ERR(handle)) {
            error = PTR_ERR(handle);
      } else {
            int error2;

            error = ext4_xattr_set_handle(handle, inode, name_index, name,
                                    value, value_len, flags);
            error2 = ext4_journal_stop(handle);
            if (error == -ENOSPC &&
                ext4_should_retry_alloc(inode->i_sb, &retries))
                  goto retry;
            if (error == 0)
                  error = error2;
      }

      return error;
}

/*
 * Shift the EA entries in the inode to create space for the increased
 * i_extra_isize.
 */
static void ext4_xattr_shift_entries(struct ext4_xattr_entry *entry,
                             int value_offs_shift, void *to,
                             void *from, size_t n, int blocksize)
{
      struct ext4_xattr_entry *last = entry;
      int new_offs;

      /* Adjust the value offsets of the entries */
      for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
            if (!last->e_value_block && last->e_value_size) {
                  new_offs = le16_to_cpu(last->e_value_offs) +
                                          value_offs_shift;
                  BUG_ON(new_offs + le32_to_cpu(last->e_value_size)
                         > blocksize);
                  last->e_value_offs = cpu_to_le16(new_offs);
            }
      }
      /* Shift the entries by n bytes */
      memmove(to, from, n);
}

/*
 * Expand an inode by new_extra_isize bytes when EAs are present.
 * Returns 0 on success or negative error number on failure.
 */
int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
                         struct ext4_inode *raw_inode, handle_t *handle)
{
      struct ext4_xattr_ibody_header *header;
      struct ext4_xattr_entry *entry, *last, *first;
      struct buffer_head *bh = NULL;
      struct ext4_xattr_ibody_find *is = NULL;
      struct ext4_xattr_block_find *bs = NULL;
      char *buffer = NULL, *b_entry_name = NULL;
      size_t min_offs, free;
      int total_ino, total_blk;
      void *base, *start, *end;
      int extra_isize = 0, error = 0, tried_min_extra_isize = 0;
      int s_min_extra_isize = le16_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_min_extra_isize);

      down_write(&EXT4_I(inode)->xattr_sem);
retry:
      if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) {
            up_write(&EXT4_I(inode)->xattr_sem);
            return 0;
      }

      header = IHDR(inode, raw_inode);
      entry = IFIRST(header);

      /*
       * Check if enough free space is available in the inode to shift the
       * entries ahead by new_extra_isize.
       */

      base = start = entry;
      end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
      min_offs = end - base;
      last = entry;
      total_ino = sizeof(struct ext4_xattr_ibody_header);

      free = ext4_xattr_free_space(last, &min_offs, base, &total_ino);
      if (free >= new_extra_isize) {
            entry = IFIRST(header);
            ext4_xattr_shift_entries(entry,     EXT4_I(inode)->i_extra_isize
                        - new_extra_isize, (void *)raw_inode +
                        EXT4_GOOD_OLD_INODE_SIZE + new_extra_isize,
                        (void *)header, total_ino,
                        inode->i_sb->s_blocksize);
            EXT4_I(inode)->i_extra_isize = new_extra_isize;
            error = 0;
            goto cleanup;
      }

      /*
       * Enough free space isn't available in the inode, check if
       * EA block can hold new_extra_isize bytes.
       */
      if (EXT4_I(inode)->i_file_acl) {
            bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
            error = -EIO;
            if (!bh)
                  goto cleanup;
            if (ext4_xattr_check_block(bh)) {
                  ext4_error(inode->i_sb, __FUNCTION__,
                        "inode %lu: bad block %llu", inode->i_ino,
                        EXT4_I(inode)->i_file_acl);
                  error = -EIO;
                  goto cleanup;
            }
            base = BHDR(bh);
            first = BFIRST(bh);
            end = bh->b_data + bh->b_size;
            min_offs = end - base;
            free = ext4_xattr_free_space(first, &min_offs, base,
                                   &total_blk);
            if (free < new_extra_isize) {
                  if (!tried_min_extra_isize && s_min_extra_isize) {
                        tried_min_extra_isize++;
                        new_extra_isize = s_min_extra_isize;
                        brelse(bh);
                        goto retry;
                  }
                  error = -1;
                  goto cleanup;
            }
      } else {
            free = inode->i_sb->s_blocksize;
      }

      while (new_extra_isize > 0) {
            size_t offs, size, entry_size;
            struct ext4_xattr_entry *small_entry = NULL;
            struct ext4_xattr_info i = {
                  .value = NULL,
                  .value_len = 0,
            };
            unsigned int total_size;  /* EA entry size + value size */
            unsigned int shift_bytes; /* No. of bytes to shift EAs by? */
            unsigned int min_total_size = ~0U;

            is = kzalloc(sizeof(struct ext4_xattr_ibody_find), GFP_NOFS);
            bs = kzalloc(sizeof(struct ext4_xattr_block_find), GFP_NOFS);
            if (!is || !bs) {
                  error = -ENOMEM;
                  goto cleanup;
            }

            is->s.not_found = -ENODATA;
            bs->s.not_found = -ENODATA;
            is->iloc.bh = NULL;
            bs->bh = NULL;

            last = IFIRST(header);
            /* Find the entry best suited to be pushed into EA block */
            entry = NULL;
            for (; !IS_LAST_ENTRY(last); last = EXT4_XATTR_NEXT(last)) {
                  total_size =
                  EXT4_XATTR_SIZE(le32_to_cpu(last->e_value_size)) +
                              EXT4_XATTR_LEN(last->e_name_len);
                  if (total_size <= free && total_size < min_total_size) {
                        if (total_size < new_extra_isize) {
                              small_entry = last;
                        } else {
                              entry = last;
                              min_total_size = total_size;
                        }
                  }
            }

            if (entry == NULL) {
                  if (small_entry) {
                        entry = small_entry;
                  } else {
                        if (!tried_min_extra_isize &&
                            s_min_extra_isize) {
                              tried_min_extra_isize++;
                              new_extra_isize = s_min_extra_isize;
                              goto retry;
                        }
                        error = -1;
                        goto cleanup;
                  }
            }
            offs = le16_to_cpu(entry->e_value_offs);
            size = le32_to_cpu(entry->e_value_size);
            entry_size = EXT4_XATTR_LEN(entry->e_name_len);
            i.name_index = entry->e_name_index,
            buffer = kmalloc(EXT4_XATTR_SIZE(size), GFP_NOFS);
            b_entry_name = kmalloc(entry->e_name_len + 1, GFP_NOFS);
            if (!buffer || !b_entry_name) {
                  error = -ENOMEM;
                  goto cleanup;
            }
            /* Save the entry name and the entry value */
            memcpy(buffer, (void *)IFIRST(header) + offs,
                   EXT4_XATTR_SIZE(size));
            memcpy(b_entry_name, entry->e_name, entry->e_name_len);
            b_entry_name[entry->e_name_len] = '\0';
            i.name = b_entry_name;

            error = ext4_get_inode_loc(inode, &is->iloc);
            if (error)
                  goto cleanup;

            error = ext4_xattr_ibody_find(inode, &i, is);
            if (error)
                  goto cleanup;

            /* Remove the chosen entry from the inode */
            error = ext4_xattr_ibody_set(handle, inode, &i, is);

            entry = IFIRST(header);
            if (entry_size + EXT4_XATTR_SIZE(size) >= new_extra_isize)
                  shift_bytes = new_extra_isize;
            else
                  shift_bytes = entry_size + size;
            /* Adjust the offsets and shift the remaining entries ahead */
            ext4_xattr_shift_entries(entry, EXT4_I(inode)->i_extra_isize -
                  shift_bytes, (void *)raw_inode +
                  EXT4_GOOD_OLD_INODE_SIZE + extra_isize + shift_bytes,
                  (void *)header, total_ino - entry_size,
                  inode->i_sb->s_blocksize);

            extra_isize += shift_bytes;
            new_extra_isize -= shift_bytes;
            EXT4_I(inode)->i_extra_isize = extra_isize;

            i.name = b_entry_name;
            i.value = buffer;
            i.value_len = size;
            error = ext4_xattr_block_find(inode, &i, bs);
            if (error)
                  goto cleanup;

            /* Add entry which was removed from the inode into the block */
            error = ext4_xattr_block_set(handle, inode, &i, bs);
            if (error)
                  goto cleanup;
            kfree(b_entry_name);
            kfree(buffer);
            brelse(is->iloc.bh);
            kfree(is);
            kfree(bs);
      }
      brelse(bh);
      up_write(&EXT4_I(inode)->xattr_sem);
      return 0;

cleanup:
      kfree(b_entry_name);
      kfree(buffer);
      if (is)
            brelse(is->iloc.bh);
      kfree(is);
      kfree(bs);
      brelse(bh);
      up_write(&EXT4_I(inode)->xattr_sem);
      return error;
}



/*
 * ext4_xattr_delete_inode()
 *
 * Free extended attribute resources associated with this inode. This
 * is called immediately before an inode is freed. We have exclusive
 * access to the inode.
 */
void
ext4_xattr_delete_inode(handle_t *handle, struct inode *inode)
{
      struct buffer_head *bh = NULL;

      if (!EXT4_I(inode)->i_file_acl)
            goto cleanup;
      bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
      if (!bh) {
            ext4_error(inode->i_sb, __FUNCTION__,
                  "inode %lu: block %llu read error", inode->i_ino,
                  EXT4_I(inode)->i_file_acl);
            goto cleanup;
      }
      if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
          BHDR(bh)->h_blocks != cpu_to_le32(1)) {
            ext4_error(inode->i_sb, __FUNCTION__,
                  "inode %lu: bad block %llu", inode->i_ino,
                  EXT4_I(inode)->i_file_acl);
            goto cleanup;
      }
      ext4_xattr_release_block(handle, inode, bh);
      EXT4_I(inode)->i_file_acl = 0;

cleanup:
      brelse(bh);
}

/*
 * ext4_xattr_put_super()
 *
 * This is called when a file system is unmounted.
 */
void
ext4_xattr_put_super(struct super_block *sb)
{
      mb_cache_shrink(sb->s_bdev);
}

/*
 * ext4_xattr_cache_insert()
 *
 * Create a new entry in the extended attribute cache, and insert
 * it unless such an entry is already in the cache.
 *
 * Returns 0, or a negative error number on failure.
 */
static void
ext4_xattr_cache_insert(struct buffer_head *bh)
{
      __u32 hash = le32_to_cpu(BHDR(bh)->h_hash);
      struct mb_cache_entry *ce;
      int error;

      ce = mb_cache_entry_alloc(ext4_xattr_cache);
      if (!ce) {
            ea_bdebug(bh, "out of memory");
            return;
      }
      error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
      if (error) {
            mb_cache_entry_free(ce);
            if (error == -EBUSY) {
                  ea_bdebug(bh, "already in cache");
                  error = 0;
            }
      } else {
            ea_bdebug(bh, "inserting [%x]", (int)hash);
            mb_cache_entry_release(ce);
      }
}

/*
 * ext4_xattr_cmp()
 *
 * Compare two extended attribute blocks for equality.
 *
 * Returns 0 if the blocks are equal, 1 if they differ, and
 * a negative error number on errors.
 */
static int
ext4_xattr_cmp(struct ext4_xattr_header *header1,
             struct ext4_xattr_header *header2)
{
      struct ext4_xattr_entry *entry1, *entry2;

      entry1 = ENTRY(header1+1);
      entry2 = ENTRY(header2+1);
      while (!IS_LAST_ENTRY(entry1)) {
            if (IS_LAST_ENTRY(entry2))
                  return 1;
            if (entry1->e_hash != entry2->e_hash ||
                entry1->e_name_index != entry2->e_name_index ||
                entry1->e_name_len != entry2->e_name_len ||
                entry1->e_value_size != entry2->e_value_size ||
                memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
                  return 1;
            if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
                  return -EIO;
            if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
                     (char *)header2 + le16_to_cpu(entry2->e_value_offs),
                     le32_to_cpu(entry1->e_value_size)))
                  return 1;

            entry1 = EXT4_XATTR_NEXT(entry1);
            entry2 = EXT4_XATTR_NEXT(entry2);
      }
      if (!IS_LAST_ENTRY(entry2))
            return 1;
      return 0;
}

/*
 * ext4_xattr_cache_find()
 *
 * Find an identical extended attribute block.
 *
 * Returns a pointer to the block found, or NULL if such a block was
 * not found or an error occurred.
 */
static struct buffer_head *
ext4_xattr_cache_find(struct inode *inode, struct ext4_xattr_header *header,
                  struct mb_cache_entry **pce)
{
      __u32 hash = le32_to_cpu(header->h_hash);
      struct mb_cache_entry *ce;

      if (!header->h_hash)
            return NULL;  /* never share */
      ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
again:
      ce = mb_cache_entry_find_first(ext4_xattr_cache, 0,
                               inode->i_sb->s_bdev, hash);
      while (ce) {
            struct buffer_head *bh;

            if (IS_ERR(ce)) {
                  if (PTR_ERR(ce) == -EAGAIN)
                        goto again;
                  break;
            }
            bh = sb_bread(inode->i_sb, ce->e_block);
            if (!bh) {
                  ext4_error(inode->i_sb, __FUNCTION__,
                        "inode %lu: block %lu read error",
                        inode->i_ino, (unsigned long) ce->e_block);
            } else if (le32_to_cpu(BHDR(bh)->h_refcount) >=
                        EXT4_XATTR_REFCOUNT_MAX) {
                  ea_idebug(inode, "block %lu refcount %d>=%d",
                          (unsigned long) ce->e_block,
                          le32_to_cpu(BHDR(bh)->h_refcount),
                                EXT4_XATTR_REFCOUNT_MAX);
            } else if (ext4_xattr_cmp(header, BHDR(bh)) == 0) {
                  *pce = ce;
                  return bh;
            }
            brelse(bh);
            ce = mb_cache_entry_find_next(ce, 0, inode->i_sb->s_bdev, hash);
      }
      return NULL;
}

#define NAME_HASH_SHIFT 5
#define VALUE_HASH_SHIFT 16

/*
 * ext4_xattr_hash_entry()
 *
 * Compute the hash of an extended attribute.
 */
static inline void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
                               struct ext4_xattr_entry *entry)
{
      __u32 hash = 0;
      char *name = entry->e_name;
      int n;

      for (n=0; n < entry->e_name_len; n++) {
            hash = (hash << NAME_HASH_SHIFT) ^
                   (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
                   *name++;
      }

      if (entry->e_value_block == 0 && entry->e_value_size != 0) {
            __le32 *value = (__le32 *)((char *)header +
                  le16_to_cpu(entry->e_value_offs));
            for (n = (le32_to_cpu(entry->e_value_size) +
                 EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
                  hash = (hash << VALUE_HASH_SHIFT) ^
                         (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
                         le32_to_cpu(*value++);
            }
      }
      entry->e_hash = cpu_to_le32(hash);
}

#undef NAME_HASH_SHIFT
#undef VALUE_HASH_SHIFT

#define BLOCK_HASH_SHIFT 16

/*
 * ext4_xattr_rehash()
 *
 * Re-compute the extended attribute hash value after an entry has changed.
 */
static void ext4_xattr_rehash(struct ext4_xattr_header *header,
                        struct ext4_xattr_entry *entry)
{
      struct ext4_xattr_entry *here;
      __u32 hash = 0;

      ext4_xattr_hash_entry(header, entry);
      here = ENTRY(header+1);
      while (!IS_LAST_ENTRY(here)) {
            if (!here->e_hash) {
                  /* Block is not shared if an entry's hash value == 0 */
                  hash = 0;
                  break;
            }
            hash = (hash << BLOCK_HASH_SHIFT) ^
                   (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
                   le32_to_cpu(here->e_hash);
            here = EXT4_XATTR_NEXT(here);
      }
      header->h_hash = cpu_to_le32(hash);
}

#undef BLOCK_HASH_SHIFT

int __init
init_ext4_xattr(void)
{
      ext4_xattr_cache = mb_cache_create("ext4_xattr", NULL,
            sizeof(struct mb_cache_entry) +
            sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 6);
      if (!ext4_xattr_cache)
            return -ENOMEM;
      return 0;
}

void
exit_ext4_xattr(void)
{
      if (ext4_xattr_cache)
            mb_cache_destroy(ext4_xattr_cache);
      ext4_xattr_cache = NULL;
}

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