ext4: give more helpful error message in ext4_ext_rm_leaf()

[mirror_ubuntu-artful-kernel.git] / fs / ext4 / 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/mbcache.h>
#include <linux/quotaops.h>
#include <linux/rwsem.h>
#include "ext4_jbd2.h"
#include "ext4.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 int ext4_xattr_list(struct dentry *dentry, char *buffer,
                           size_t buffer_size);

static struct mb_cache *ext4_xattr_cache;

static const struct xattr_handler *ext4_xattr_handler_map[] = {
        [EXT4_XATTR_INDEX_USER]              = &ext4_xattr_user_handler,
#ifdef CONFIG_EXT4_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_EXT4_FS_SECURITY
        [EXT4_XATTR_INDEX_SECURITY]          = &ext4_xattr_security_handler,
#endif
};

const struct xattr_handler *ext4_xattr_handlers[] = {
        &ext4_xattr_user_handler,
        &ext4_xattr_trusted_handler,
#ifdef CONFIG_EXT4_FS_POSIX_ACL
        &ext4_xattr_acl_access_handler,
        &ext4_xattr_acl_default_handler,
#endif
#ifdef CONFIG_EXT4_FS_SECURITY
        &ext4_xattr_security_handler,
#endif
        NULL
};

static inline const struct xattr_handler *
ext4_xattr_handler(int name_index)
{
        const 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, 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)
{
        if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
            BHDR(bh)->h_blocks != cpu_to_le32(1))
                return -EIO;
        return ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size);
}

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(inode, "bad block %llu",
                                 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_test_inode_state(inode, 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 dentry *dentry, 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)) {
                const struct xattr_handler *handler =
                        ext4_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
ext4_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 (!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(inode, "bad block %llu",
                                 EXT4_I(inode)->i_file_acl);
                error = -EIO;
                goto cleanup;
        }
        ext4_xattr_cache_insert(bh);
        error = ext4_xattr_list_entries(dentry, BFIRST(bh), buffer, buffer_size);

cleanup:
        brelse(bh);

        return error;
}

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

        if (!ext4_test_inode_state(inode, 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(dentry, 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.
 */
static int
ext4_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
        int ret, ret2;

        down_read(&EXT4_I(dentry->d_inode)->xattr_sem);
        ret = ret2 = ext4_xattr_ibody_list(dentry, buffer, buffer_size);
        if (ret < 0)
                goto errout;
        if (buffer) {
                buffer += ret;
                buffer_size -= ret;
        }
        ret = ext4_xattr_block_list(dentry, buffer, buffer_size);
        if (ret < 0)
                goto errout;
        ret += ret2;
errout:
        up_read(&EXT4_I(dentry->d_inode)->xattr_sem);
        return ret;
}

/*
 * 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);
                ext4_handle_dirty_super(handle, sb);
        }
}

/*
 * 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);
                get_bh(bh);
                ext4_free_blocks(handle, inode, bh, 0, 1,
                                 EXT4_FREE_BLOCKS_METADATA |
                                 EXT4_FREE_BLOCKS_FORGET);
                unlock_buffer(bh);
        } else {
                le32_add_cpu(&BHDR(bh)->h_refcount, -1);
                if (ce)
                        mb_cache_entry_release(ce);
                unlock_buffer(bh);
                error = ext4_handle_dirty_metadata(handle, inode, bh);
                if (IS_SYNC(inode))
                        ext4_handle_sync(handle);
                dquot_free_block(inode, 1);
                ea_bdebug(bh, "refcount now=%d; releasing",
                          le32_to_cpu(BHDR(bh)->h_refcount));
        }
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_INODE(inode, "bad block %llu",
                                         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_handle_dirty_metadata(handle,
                                                                   inode,
                                                                   bs->bh);
                        if (error)
                                goto cleanup;
                        goto inserted;
                } else {
                        int offset = (char *)s->here - bs->bh->b_data;

                        unlock_buffer(bs->bh);
                        ext4_handle_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(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 = dquot_alloc_block(inode, 1);
                                if (error)
                                        goto cleanup;
                                error = ext4_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 = ext4_handle_dirty_metadata(handle,
                                                                   inode,
                                                                   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, block;

                        goal = ext4_group_first_block_no(sb,
                                                EXT4_I(inode)->i_block_group);

                        /* non-extent files can't have physical blocks past 2^32 */
                        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
                                goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;

                        /*
                         * take i_data_sem because we will test
                         * i_delalloc_reserved_flag in ext4_mb_new_blocks
                         */
                        down_read((&EXT4_I(inode)->i_data_sem));
                        block = ext4_new_meta_blocks(handle, inode, goal, 0,
                                                     NULL, &error);
                        up_read((&EXT4_I(inode)->i_data_sem));
                        if (error)
                                goto cleanup;

                        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
                                BUG_ON(block > EXT4_MAX_BLOCK_FILE_PHYS);

                        ea_idebug(inode, "creating block %d", block);

                        new_bh = sb_getblk(sb, block);
                        if (!new_bh) {
getblk_failed:
                                ext4_free_blocks(handle, inode, NULL, block, 1,
                                                 EXT4_FREE_BLOCKS_METADATA);
                                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_handle_dirty_metadata(handle,
                                                           inode, 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(inode, "bad block %llu",
                         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_test_inode_state(inode, 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_set_inode_state(inode, EXT4_STATE_XATTR);
        } else {
                header->h_magic = cpu_to_le32(0);
                ext4_clear_inode_state(inode, EXT4_STATE_XATTR);
        }
        return 0;
}

/*
 * ext4_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
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, },
        };
        unsigned long no_expand;
        int error;

        if (!name)
                return -EINVAL;
        if (strlen(name) > 255)
                return -ERANGE;
        down_write(&EXT4_I(inode)->xattr_sem);
        no_expand = ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND);
        ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);

        error = ext4_reserve_inode_write(handle, inode, &is.iloc);
        if (error)
                goto cleanup;

        if (ext4_test_inode_state(inode, 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_clear_inode_state(inode, 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;
        }
        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) {
                        if (EXT4_I(inode)->i_file_acl && !bs.s.base) {
                                error = ext4_xattr_block_find(inode, &i, &bs);
                                if (error)
                                        goto cleanup;
                        }
                        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_clear_inode_state(inode, 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))
                        ext4_handle_sync(handle);
        }

cleanup:
        brelse(is.iloc.bh);
        brelse(bs.bh);
        if (no_expand == 0)
                ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
        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(inode, "bad block %llu",
                                         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);
                if (error)
                        goto cleanup;

                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);
                b_entry_name = NULL;
                buffer = NULL;
                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(inode, "block %llu read error",
                                 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(inode, "bad block %llu",
                                 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, 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);
        }
}

/*
 * 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, 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(inode, "block %lu read error",
                                         (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, 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
ext4_init_xattr(void)
{
        ext4_xattr_cache = mb_cache_create("ext4_xattr", 6);
        if (!ext4_xattr_cache)
                return -ENOMEM;
        return 0;
}

void
ext4_exit_xattr(void)
{
        if (ext4_xattr_cache)
                mb_cache_destroy(ext4_xattr_cache);
        ext4_xattr_cache = NULL;
}