Commit fb30f470 authored by Omar Sandoval's avatar Omar Sandoval Committed by David Sterba
Browse files

btrfs: clarify btrfs_lookup_bio_sums documentation 



Fix a couple of issues in the btrfs_lookup_bio_sums documentation:

* The bio doesn't need to be a btrfs_io_bio if dst was provided. Move
  the declaration in the code to make that clear, too.
* dst must be large enough to hold nblocks * csum_size, not just
  csum_size.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent f337bd74

fs/btrfs/file-item.c

+7 −4
Original line number Diff line number Diff line
@@ -242,11 +242,13 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans, 
/**

 * btrfs_lookup_bio_sums - Look up checksums for a bio.

 * @inode: inode that the bio is for.

 * @bio: bio embedded in btrfs_io_bio.

 * @bio: bio to look up.

 * @offset: Unless (u64)-1, look up checksums for this offset in the file.

 *          If (u64)-1, use the page offsets from the bio instead.

 * @dst: Buffer of size btrfs_super_csum_size() used to return checksum. If

 *       NULL, the checksum is returned in btrfs_io_bio(bio)->csum instead.

 * @dst: Buffer of size nblocks * btrfs_super_csum_size() used to return

 *       checksum (nblocks = bio->bi_iter.bi_size / fs_info->sectorsize). If

 *       NULL, the checksum buffer is allocated and returned in

 *       btrfs_io_bio(bio)->csum instead.

 *

 * Return: BLK_STS_RESOURCE if allocating memory fails, BLK_STS_OK otherwise.

 */
@@ -256,7 +258,6 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, 
	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	struct bio_vec bvec;

	struct bvec_iter iter;

	struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);

	struct btrfs_csum_item *item = NULL;

	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;

	struct btrfs_path *path;
@@ -277,6 +278,8 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, 


	nblocks = bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;

	if (!dst) {

		struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);



		if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) {

			btrfs_bio->csum = kmalloc_array(nblocks, csum_size,

							GFP_NOFS);

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