btrfs: introduce a data checksum checking helper

Although we have several data csum verification code, we never have a
function really just to verify checksum for one sector.

Function check_data_csum() do extra work for error reporting, thus it
requires a lot of extra things like file offset, bio_offset etc.

Function btrfs_verify_data_csum() is even worse, it will utilize page
checked flag, which means it can not be utilized for direct IO pages.

Here we introduce a new helper, btrfs_check_sector_csum(), which really
only accept a sector in page, and expected checksum pointer.

We use this function to implement check_data_csum(), and export it for
incoming patch.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
[hch: keep passing the csum array as an arguments, as the callers want
      to print it, rename per request]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ad31cc5cdd50..6e65778040ed 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3253,6 +3253,8 @@ u64 btrfs_file_extent_end(const struct btrfs_path *path);
 /* inode.c */
 void btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 			   int mirror_num, enum btrfs_compression_type compress_type);
+int btrfs_check_sector_csum(struct btrfs_fs_info *fs_info, struct page *page,
+			    u32 pgoff, u8 *csum, const u8 * const csum_expected);
 unsigned int btrfs_verify_data_csum(struct btrfs_bio *bbio,
 				    u32 bio_offset, struct page *page,
 				    u64 start, u64 end);