xattr.c

linux 内核源代码

	if (EXT3_I(inode)->i_state & 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_I(inode)->i_state |= EXT3_STATE_XATTR;
	} else {
		header->h_magic = cpu_to_le32(0);
		EXT3_I(inode)->i_state &= ~EXT3_STATE_XATTR;
	}
	return 0;
}

/*
 * ext3_xattr_set_handle()
 *
 * Create, replace or remove an extended attribute for this inode. Buffer
 * is NULL to remove an existing extended attribute, and non-NULL to
 * either replace an existing extended attribute, or create a new extended
 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 * specify that an extended attribute must exist and must not exist
 * previous to the call, respectively.
 *
 * Returns 0, or a negative error number on failure.
 */
int
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;

	if (EXT3_I(inode)->i_state & 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_I(inode)->i_state &= ~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;
	}
	error = ext3_journal_get_write_access(handle, is.iloc.bh);
	if (error)
		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) {
			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, __FUNCTION__,
			"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, __FUNCTION__,
			"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);
	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, 0,
				       inode->i_sb->s_bdev, hash);
	while (ce) {
		struct buffer_head *bh;

		if (IS_ERR(ce)) {
			if (PTR_ERR(ce) == -EAGAIN)
				goto again;
			break;
		}
		bh = sb_bread(inode->i_sb, ce->e_block);
		if (!bh) {
			ext3_error(inode->i_sb, __FUNCTION__,
				"inode %lu: block %lu read error",
				inode->i_ino, (unsigned long) ce->e_block);
		} else if (le32_to_cpu(BHDR(bh)->h_refcount) >=
				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, 0, 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", NULL,
		sizeof(struct mb_cache_entry) +
		sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]), 1, 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;
}