xattr.c

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/*
 * linux/fs/ext3/xattr.c
 *
 * Copyright (C) 2001-2003 Andreas Gruenbacher, <[email protected]>
 *
 * Fix by Harrison Xing <[email protected]>.
 * Ext3 code with a lot of help from Eric Jarman <[email protected]>.
 * Extended attributes for symlinks and special files added per
 *  suggestion of Luka Renko <[email protected]>.
 * xattr consolidation Copyright (c) 2004 James Morris <[email protected]>,
 *  Red Hat Inc.
 * ea-in-inode support by Alex Tomas <[email protected]> aka bzzz
 *  and Andreas Gruenbacher <[email protected]>.
 */

/*
 * 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
 * ----------------
 * EXT3_I(inode)->i_file_acl is protected by EXT3_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 "ext3.h"
#include <linux/mbcache.h>
#include <linux/quotaops.h>
#include "xattr.h"
#include "acl.h"

#define BHDR(bh) ((struct ext3_xattr_header *)((bh)->b_data))
#define ENTRY(ptr) ((struct ext3_xattr_entry *)(ptr))
#define BFIRST(bh) ENTRY(BHDR(bh)+1)
#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)

#define IHDR(inode, raw_inode) \
    ((struct ext3_xattr_ibody_header *) \
        ((void *)raw_inode + \
         EXT3_GOOD_OLD_INODE_SIZE + \
         EXT3_I(inode)->i_extra_isize))
#define IFIRST(hdr) ((struct ext3_xattr_entry *)((hdr)+1))

#ifdef EXT3_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 ext3_xattr_cache_insert(struct buffer_head *);
static struct buffer_head *ext3_xattr_cache_find(struct inode *,
                         struct ext3_xattr_header *,
                         struct mb_cache_entry **);
static void ext3_xattr_rehash(struct ext3_xattr_header *,
                  struct ext3_xattr_entry *);
static int ext3_xattr_list(struct dentry *dentry, char *buffer,
               size_t buffer_size);

static struct mb_cache *ext3_xattr_cache;

static const struct xattr_handler *ext3_xattr_handler_map[] = {
    [EXT3_XATTR_INDEX_USER]          = &ext3_xattr_user_handler,
#ifdef CONFIG_EXT3_FS_POSIX_ACL
    [EXT3_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext3_xattr_acl_access_handler,
    [EXT3_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext3_xattr_acl_default_handler,
#endif
    [EXT3_XATTR_INDEX_TRUSTED]       = &ext3_xattr_trusted_handler,
#ifdef CONFIG_EXT3_FS_SECURITY
    [EXT3_XATTR_INDEX_SECURITY]      = &ext3_xattr_security_handler,
#endif
};

const struct xattr_handler *ext3_xattr_handlers[] = {
    &ext3_xattr_user_handler,
    &ext3_xattr_trusted_handler,
#ifdef CONFIG_EXT3_FS_POSIX_ACL
    &ext3_xattr_acl_access_handler,
    &ext3_xattr_acl_default_handler,
#endif
#ifdef CONFIG_EXT3_FS_SECURITY
    &ext3_xattr_security_handler,
#endif
    NULL
};

static inline const struct xattr_handler *
ext3_xattr_handler(int name_index)
{
    const struct xattr_handler *handler = NULL;

    if (name_index > 0 && name_index < ARRAY_SIZE(ext3_xattr_handler_map))
        handler = ext3_xattr_handler_map[name_index];
    return handler;
}

/*
 * Inode operation listxattr()
 *
 * dentry->d_inode->i_mutex: don't care
 */
ssize_t
ext3_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
    return ext3_xattr_list(dentry, buffer, size);
}

static int
ext3_xattr_check_names(struct ext3_xattr_entry *entry, void *end)
{
    while (!IS_LAST_ENTRY(entry)) {
        struct ext3_xattr_entry *next = EXT3_XATTR_NEXT(entry);
        if ((void *)next >= end)
            return -EIO;
        entry = next;
    }
    return 0;
}

static inline int
ext3_xattr_check_block(struct buffer_head *bh)
{
    int error;

    if (BHDR(bh)->h_magic != cpu_to_le32(EXT3_XATTR_MAGIC) ||
        BHDR(bh)->h_blocks != cpu_to_le32(1))
        return -EIO;
    error = ext3_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
    return error;
}

static inline int
ext3_xattr_check_entry(struct ext3_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
ext3_xattr_find_entry(struct ext3_xattr_entry **pentry, int name_index,
              const char *name, size_t size, int sorted)
{
    struct ext3_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 = EXT3_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 && ext3_xattr_check_entry(entry, size))
            return -EIO;
    return cmp ? -ENODATA : 0;
}

static int
ext3_xattr_block_get(struct inode *inode, int name_index, const char *name,
             void *buffer, size_t buffer_size)
{
    struct buffer_head *bh = NULL;
    struct ext3_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 (!EXT3_I(inode)->i_file_acl)
        goto cleanup;
    ea_idebug(inode, "reading block %u", EXT3_I(inode)->i_file_acl);
    bh = sb_bread(inode->i_sb, EXT3_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 (ext3_xattr_check_block(bh)) {
bad_block:  ext3_error(inode->i_sb, __func__,
               "inode %lu: bad block "E3FSBLK, inode->i_ino,
               EXT3_I(inode)->i_file_acl);
        error = -EIO;
        goto cleanup;
    }
    ext3_xattr_cache_insert(bh);
    entry = BFIRST(bh);
    error = ext3_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
ext3_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
             void *buffer, size_t buffer_size)
{
    struct ext3_xattr_ibody_header *header;
    struct ext3_xattr_entry *entry;
    struct ext3_inode *raw_inode;
    struct ext3_iloc iloc;
    size_t size;
    void *end;
    int error;

    if (!ext3_test_inode_state(inode, EXT3_STATE_XATTR))
        return -ENODATA;
    error = ext3_get_inode_loc(inode, &iloc);
    if (error)
        return error;
    raw_inode = ext3_raw_inode(&iloc);
    header = IHDR(inode, raw_inode);
    entry = IFIRST(header);
    end = (void *)raw_inode + EXT3_SB(inode->i_sb)->s_inode_size;
    error = ext3_xattr_check_names(entry, end);
    if (error)
        goto cleanup;
    error = ext3_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;
}

/*
 * ext3_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
ext3_xattr_get(struct inode *inode, int name_index, const char *name,
           void *buffer, size_t buffer_size)
{
    int error;

    down_read(&EXT3_I(inode)->xattr_sem);
    error = ext3_xattr_ibody_get(inode, name_index, name, buffer,
                     buffer_size);
    if (error == -ENODATA)
        error = ext3_xattr_block_get(inode, name_index, name, buffer,
                         buffer_size);
    up_read(&EXT3_I(inode)->xattr_sem);
    return error;
}

static int
ext3_xattr_list_entries(struct dentry *dentry, struct ext3_xattr_entry *entry,
            char *buffer, size_t buffer_size)
{
    size_t rest = buffer_size;

    for (; !IS_LAST_ENTRY(entry); entry = EXT3_XATTR_NEXT(entry)) {
        const struct xattr_handler *handler =
            ext3_xattr_handler(entry->e_name_index);

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

static int
ext3_xattr_block_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
    struct inode *inode = dentry->d_inode;
    struct buffer_head *bh = NULL;
    int error;

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

    error = 0;
    if (!EXT3_I(inode)->i_file_acl)
        goto cleanup;
    ea_idebug(inode, "reading block %u", EXT3_I(inode)->i_file_acl);
    bh = sb_bread(inode->i_sb, EXT3_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 (ext3_xattr_check_block(bh)) {
        ext3_error(inode->i_sb, __func__,
               "inode %lu: bad block "E3FSBLK, inode->i_ino,
               EXT3_I(inode)->i_file_acl);
        error = -EIO;
        goto cleanup;
    }
    ext3_xattr_cache_insert(bh);
    error = ext3_xattr_list_entries(dentry, BFIRST(bh), buffer, buffer_size);

cleanup:
    brelse(bh);

    return error;
}

static int
ext3_xattr_ibody_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
    struct inode *inode = dentry->d_inode;
    struct ext3_xattr_ibody_header *header;
    struct ext3_inode *raw_inode;
    struct ext3_iloc iloc;
    void *end;
    int error;

    if (!ext3_test_inode_state(inode, EXT3_STATE_XATTR))
        return 0;
    error = ext3_get_inode_loc(inode, &iloc);
    if (error)
        return error;
    raw_inode = ext3_raw_inode(&iloc);
    header = IHDR(inode, raw_inode);
    end = (void *)raw_inode + EXT3_SB(inode->i_sb)->s_inode_size;
    error = ext3_xattr_check_names(IFIRST(header), end);
    if (error)
        goto cleanup;
    error = ext3_xattr_list_entries(dentry, IFIRST(header),
                    buffer, buffer_size);

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

/*
 * ext3_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.
 */
static int
ext3_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
    int i_error, b_error;

    down_read(&EXT3_I(dentry->d_inode)->xattr_sem);
    i_error = ext3_xattr_ibody_list(dentry, buffer, buffer_size);
    if (i_error < 0) {
        b_error = 0;
    } else {
        if (buffer) {
            buffer += i_error;
            buffer_size -= i_error;
        }
        b_error = ext3_xattr_block_list(dentry, buffer, buffer_size);
        if (b_error < 0)
            i_error = 0;
    }
    up_read(&EXT3_I(dentry->d_inode)->xattr_sem);
    return i_error + b_error;
}

/*
 * If the EXT3_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 * not set, set it.
 */
static void ext3_xattr_update_super_block(handle_t *handle,
                      struct super_block *sb)
{
    if (EXT3_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_EXT_ATTR))
        return;

    if (ext3_journal_get_write_access(handle, EXT3_SB(sb)->s_sbh) == 0) {
        EXT3_SET_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_EXT_ATTR);
        ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);
    }
}

/*
 * Release the xattr block BH: If the reference count is > 1, decrement
 * it; otherwise free the block.
 */
static void
ext3_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(ext3_xattr_cache, bh->b_bdev, bh->b_blocknr);
    error = ext3_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);
        ext3_free_blocks(handle, inode, bh->b_blocknr, 1);
        get_bh(bh);
        ext3_forget(handle, 1, inode, bh, bh->b_blocknr);
    } else {
        le32_add_cpu(&BHDR(bh)->h_refcount, -1);
        error = ext3_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:
    ext3_std_error(inode->i_sb, error);
    return;
}

struct ext3_xattr_info {
    int name_index;
    const char *name;
    const void *value;
    size_t value_len;
};

struct ext3_xattr_search {
    struct ext3_xattr_entry *first;
    void *base;
    void *end;
    struct ext3_xattr_entry *here;
    int not_found;
};

static int
ext3_xattr_set_entry(struct ext3_xattr_info *i, struct ext3_xattr_search *s)
{
    struct ext3_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 = EXT3_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 += EXT3_XATTR_SIZE(size);
        }
        free += EXT3_XATTR_LEN(name_len);
    }
    if (i->value) {
        if (free < EXT3_XATTR_SIZE(i->value_len) ||
            free < EXT3_XATTR_LEN(name_len) +
               EXT3_XATTR_SIZE(i->value_len))
            return -ENOSPC;
    }

    if (i->value && s->not_found) {
        /* Insert the new name. */
        size_t size = EXT3_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 = EXT3_XATTR_SIZE(
                le32_to_cpu(s->here->e_value_size));

            if (i->value && size == EXT3_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 - EXT3_XATTR_PAD, 0,
                       EXT3_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 = EXT3_XATTR_NEXT(last);
            }
        }
        if (!i->value) {
            /* Remove the old name. */
            size_t size = EXT3_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 = EXT3_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 - EXT3_XATTR_PAD, 0,
                   EXT3_XATTR_PAD); /* Clear the pad bytes. */
            memcpy(val, i->value, i->value_len);
        }
    }
    return 0;
}

struct ext3_xattr_block_find {
    struct ext3_xattr_search s;
    struct buffer_head *bh;
};

static int
ext3_xattr_block_find(struct inode *inode, struct ext3_xattr_info *i,
              struct ext3_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 (EXT3_I(inode)->i_file_acl) {
        /* The inode already has an extended attribute block. */
        bs->bh = sb_bread(sb, EXT3_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 (ext3_xattr_check_block(bs->bh)) {
            ext3_error(sb, __func__,
                "inode %lu: bad block "E3FSBLK, inode->i_ino,
                EXT3_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 = ext3_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
ext3_xattr_block_set(handle_t *handle, struct inode *inode,
             struct ext3_xattr_info *i,
             struct ext3_xattr_block_find *bs)
{
    struct super_block *sb = inode->i_sb;
    struct buffer_head *new_bh = NULL;
    struct ext3_xattr_search *s = &bs->s;
    struct mb_cache_entry *ce = NULL;
    int error = 0;

#define header(x) ((struct ext3_xattr_header *)(x))

    if (i->value && i->value_len > sb->s_blocksize)
        return -ENOSPC;
    if (s->base) {
        ce = mb_cache_entry_get(ext3_xattr_cache, bs->bh->b_bdev,
                    bs->bh->b_blocknr);
        error = ext3_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 = ext3_xattr_set_entry(i, s);
            if (!error) {
                if (!IS_LAST_ENTRY(s->first))
                    ext3_xattr_rehash(header(s->base),
                              s->here);
                ext3_xattr_cache_insert(bs->bh);
            }
            unlock_buffer(bs->bh);
            if (error == -EIO)
                goto bad_block;
            if (!error)
                error = ext3_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);
            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_NOFS);
            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_NOFS);
        /* assert(header == s->base) */
        error = -ENOMEM;
        if (s->base == NULL)
            goto cleanup;
        header(s->base)->h_magic = cpu_to_le32(EXT3_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 = ext3_xattr_set_entry(i, s);
    if (error == -EIO)
        goto bad_block;
    if (error)
        goto cleanup;
    if (!IS_LAST_ENTRY(s->first))
        ext3_xattr_rehash(header(s->base), s->here);

inserted:
    if (!IS_LAST_ENTRY(s->first)) {
        new_bh = ext3_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 = dquot_alloc_block(inode, 1);
                if (error)
                    goto cleanup;
                error = ext3_journal_get_write_access(handle,
                                      new_bh);
                if (error)
                    goto cleanup_dquot;
                lock_buffer(new_bh);
                le32_add_cpu(&BHDR(new_bh)->h_refcount, 1);
                ea_bdebug(new_bh, "reusing; refcount now=%d",
                    le32_to_cpu(BHDR(new_bh)->h_refcount));
                unlock_buffer(new_bh);
                error = ext3_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 */
            ext3_fsblk_t goal = ext3_group_first_block_no(sb,
                        EXT3_I(inode)->i_block_group);
            ext3_fsblk_t block;

            /*
             * Protect us agaist concurrent allocations to the
             * same inode from ext3_..._writepage(). Reservation
             * code does not expect racing allocations.
             */
            mutex_lock(&EXT3_I(inode)->truncate_mutex);
            block = ext3_new_block(handle, inode, goal, &error);
            mutex_unlock(&EXT3_I(inode)->truncate_mutex);
            if (error)
                goto cleanup;
            ea_idebug(inode, "creating block %d", block);

            new_bh = sb_getblk(sb, block);
            if (!new_bh) {
getblk_failed:
                ext3_free_blocks(handle, inode, block, 1);
                error = -EIO;
                goto cleanup;
            }
            lock_buffer(new_bh);
            error = ext3_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);
            ext3_xattr_cache_insert(new_bh);
            error = ext3_journal_dirty_metadata(handle, new_bh);
            if (error)
                goto cleanup;
        }
    }

    /* Update the inode. */
    EXT3_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;

    /* Drop the previous xattr block. */
    if (bs->bh && bs->bh != new_bh)
        ext3_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:
    ext3_error(inode->i_sb, __func__,
           "inode %lu: bad block "E3FSBLK, inode->i_ino,
           EXT3_I(inode)->i_file_acl);
    goto cleanup;

#undef header
}

struct ext3_xattr_ibody_find {
    struct ext3_xattr_search s;
    struct ext3_iloc iloc;
};

static int
ext3_xattr_ibody_find(struct inode *inode, struct ext3_xattr_info *i,
              struct ext3_xattr_ibody_find *is)
{
    struct ext3_xattr_ibody_header *header;
    struct ext3_inode *raw_inode;
    int error;

    if (EXT3_I(inode)->i_extra_isize == 0)
        return 0;
    raw_inode = ext3_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 + EXT3_SB(inode->i_sb)->s_inode_size;
    if (ext3_test_inode_state(inode, EXT3_STATE_XATTR)) {
        error = ext3_xattr_check_names(IFIRST(header), is->s.end);
        if (error)
            return error;
        /* Find the named attribute. */
        error = ext3_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
ext3_xattr_ibody_set(handle_t *handle, struct inode *inode,
             struct ext3_xattr_info *i,
             struct ext3_xattr_ibody_find *is)
{
    struct ext3_xattr_ibody_header *header;
    struct ext3_xattr_search *s = &is->s;
    int error;

    if (EXT3_I(inode)->i_extra_isize == 0)
        return -ENOSPC;
    error = ext3_xattr_set_entry(i, s);
    if (error)
        return error;
    header = IHDR(inode, ext3_raw_inode(&is->iloc));
    if (!IS_LAST_ENTRY(s->first)) {
        header->h_magic = cpu_to_le32(EXT3_XATTR_MAGIC);
        ext3_set_inode_state(inode, EXT3_STATE_XATTR);
    } else {
        header->h_magic = cpu_to_le32(0);
        ext3_clear_inode_state(inode, EXT3_STATE_XATTR);
    }
    return 0;
}

/*
 * ext3_xattr_set_handle()
 *
 * Create, replace or remove an extended attribute for this inode.  Value
 * 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
ext3_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 ext3_xattr_info i = {
        .name_index = name_index,
        .name = name,
        .value = value,
        .value_len = value_len,

    };
    struct ext3_xattr_ibody_find is = {
        .s = { .not_found = -ENODATA, },
    };
    struct ext3_xattr_block_find bs = {
        .s = { .not_found = -ENODATA, },
    };
    int error;

    if (!name)
        return -EINVAL;
    if (strlen(name) > 255)
        return -ERANGE;
    down_write(&EXT3_I(inode)->xattr_sem);
    error = ext3_get_inode_loc(inode, &is.iloc);
    if (error)
        goto cleanup;

    error = ext3_journal_get_write_access(handle, is.iloc.bh);
    if (error)
        goto cleanup;

    if (ext3_test_inode_state(inode, EXT3_STATE_NEW)) {
        struct ext3_inode *raw_inode = ext3_raw_inode(&is.iloc);
        memset(raw_inode, 0, EXT3_SB(inode->i_sb)->s_inode_size);
        ext3_clear_inode_state(inode, EXT3_STATE_NEW);
    }

    error = ext3_xattr_ibody_find(inode, &i, &is);
    if (error)
        goto cleanup;
    if (is.s.not_found)
        error = ext3_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;
    }
    if (!value) {
        if (!is.s.not_found)
            error = ext3_xattr_ibody_set(handle, inode, &i, &is);
        else if (!bs.s.not_found)
            error = ext3_xattr_block_set(handle, inode, &i, &bs);
    } else {
        error = ext3_xattr_ibody_set(handle, inode, &i, &is);
        if (!error && !bs.s.not_found) {
            i.value = NULL;
            error = ext3_xattr_block_set(handle, inode, &i, &bs);
        } else if (error == -ENOSPC) {
            if (EXT3_I(inode)->i_file_acl && !bs.s.base) {
                error = ext3_xattr_block_find(inode, &i, &bs);
                if (error)
                    goto cleanup;
            }
            error = ext3_xattr_block_set(handle, inode, &i, &bs);
            if (error)
                goto cleanup;
            if (!is.s.not_found) {
                i.value = NULL;
                error = ext3_xattr_ibody_set(handle, inode, &i,
                                 &is);
            }
        }
    }
    if (!error) {
        ext3_xattr_update_super_block(handle, inode->i_sb);
        inode->i_ctime = CURRENT_TIME_SEC;
        error = ext3_mark_iloc_dirty(handle, inode, &is.iloc);
        /*
         * The bh is consumed by ext3_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(&EXT3_I(inode)->xattr_sem);
    return error;
}

/*
 * ext3_xattr_set()
 *
 * Like ext3_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
ext3_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 = ext3_journal_start(inode, EXT3_DATA_TRANS_BLOCKS(inode->i_sb));
    if (IS_ERR(handle)) {
        error = PTR_ERR(handle);
    } else {
        int error2;

        error = ext3_xattr_set_handle(handle, inode, name_index, name,
                          value, value_len, flags);
        error2 = ext3_journal_stop(handle);
        if (error == -ENOSPC &&
            ext3_should_retry_alloc(inode->i_sb, &retries))
            goto retry;
        if (error == 0)
            error = error2;
    }

    return error;
}

/*
 * ext3_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
ext3_xattr_delete_inode(handle_t *handle, struct inode *inode)
{
    struct buffer_head *bh = NULL;

    if (!EXT3_I(inode)->i_file_acl)
        goto cleanup;
    bh = sb_bread(inode->i_sb, EXT3_I(inode)->i_file_acl);
    if (!bh) {
        ext3_error(inode->i_sb, __func__,
            "inode %lu: block "E3FSBLK" read error", inode->i_ino,
            EXT3_I(inode)->i_file_acl);
        goto cleanup;
    }
    if (BHDR(bh)->h_magic != cpu_to_le32(EXT3_XATTR_MAGIC) ||
        BHDR(bh)->h_blocks != cpu_to_le32(1)) {
        ext3_error(inode->i_sb, __func__,
            "inode %lu: bad block "E3FSBLK, inode->i_ino,
            EXT3_I(inode)->i_file_acl);
        goto cleanup;
    }
    ext3_xattr_release_block(handle, inode, bh);
    EXT3_I(inode)->i_file_acl = 0;

cleanup:
    brelse(bh);
}

/*
 * ext3_xattr_put_super()
 *
 * This is called when a file system is unmounted.
 */
void
ext3_xattr_put_super(struct super_block *sb)
{
    mb_cache_shrink(sb->s_bdev);
}

/*
 * ext3_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
ext3_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(ext3_xattr_cache, GFP_NOFS);
    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);
    }
}

/*
 * ext3_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
ext3_xattr_cmp(struct ext3_xattr_header *header1,
           struct ext3_xattr_header *header2)
{
    struct ext3_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 = EXT3_XATTR_NEXT(entry1);
        entry2 = EXT3_XATTR_NEXT(entry2);
    }
    if (!IS_LAST_ENTRY(entry2))
        return 1;
    return 0;
}

/*
 * ext3_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 *
ext3_xattr_cache_find(struct inode *inode, struct ext3_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(ext3_xattr_cache, 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) {
            ext3_error(inode->i_sb, __func__,
                "inode %lu: block %lu read error",
                inode->i_ino, (unsigned long) ce->e_block);
        } else if (le32_to_cpu(BHDR(bh)->h_refcount) >=
                EXT3_XATTR_REFCOUNT_MAX) {
            ea_idebug(inode, "block %lu refcount %d>=%d",
                  (unsigned long) ce->e_block,
                  le32_to_cpu(BHDR(bh)->h_refcount),
                      EXT3_XATTR_REFCOUNT_MAX);
        } else if (ext3_xattr_cmp(header, BHDR(bh)) == 0) {
            *pce = ce;
            return bh;
        }
        brelse(bh);
        ce = mb_cache_entry_find_next(ce, inode->i_sb->s_bdev, hash);
    }
    return NULL;
}

#define NAME_HASH_SHIFT 5
#define VALUE_HASH_SHIFT 16

/*
 * ext3_xattr_hash_entry()
 *
 * Compute the hash of an extended attribute.
 */
static inline void ext3_xattr_hash_entry(struct ext3_xattr_header *header,
                     struct ext3_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) +
             EXT3_XATTR_ROUND) >> EXT3_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

/*
 * ext3_xattr_rehash()
 *
 * Re-compute the extended attribute hash value after an entry has changed.
 */
static void ext3_xattr_rehash(struct ext3_xattr_header *header,
                  struct ext3_xattr_entry *entry)
{
    struct ext3_xattr_entry *here;
    __u32 hash = 0;

    ext3_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 = EXT3_XATTR_NEXT(here);
    }
    header->h_hash = cpu_to_le32(hash);
}

#undef BLOCK_HASH_SHIFT

int __init
init_ext3_xattr(void)
{
    ext3_xattr_cache = mb_cache_create("ext3_xattr", 6);
    if (!ext3_xattr_cache)
        return -ENOMEM;
    return 0;
}

void
exit_ext3_xattr(void)
{
    if (ext3_xattr_cache)
        mb_cache_destroy(ext3_xattr_cache);
    ext3_xattr_cache = NULL;
}