On 9.03.20 г. 23:32 ч., Omar Sandoval wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> 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.
>
> Signed-off-by: Omar Sandoval <osandov@xxxxxx>
> ---
> fs/btrfs/file-item.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index 6c849e8fd5a1..fa9f4a92f74d 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -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 / sectorsize). If NULL, the
nit: sector here refers to btrfs' notion of a sector which is 4k and not
the default understanding of 512 bytes. Dunno if it makes sense to make
that a bit more emphatic. Also nblocks is really number of checksums.
Looking at file-item.c I see there is only 1 menition of ncsums or
csums_in_item. I guess if we can make that nblocks a bit more explicit?
> + * 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);
>
