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btrfs: look at full bi_io_vec for repair decision

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Read repair does two things: it finds a good copy of data to return to
the reader, and it corrects the bad copy on disk. If a read of multiple
sectors has an I/O error, repair does an extra "validation" step that
issues a separate read for each sector. This allows us to find the exact
failing sectors and only rewrite those.

This heuristic is implemented in
bio_readpage_error()/btrfs_check_repairable() as:

	failed_bio_pages = failed_bio->bi_iter.bi_size >> PAGE_SHIFT;
	if (failed_bio_pages > 1)
		do validation

However, at this point, bi_iter may have already been advanced. This
means that we'll skip the validation step and rewrite the entire failed
read.

Fix it by getting the actual size from the biovec (which we can do
because this is only called for non-cloned bios, although that will
change in a later commit).

Fixes: 8a2ee44a37 ("btrfs: look at bi_size for repair decisions")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Omar Sandoval
2020-04-16 14:46:14 -07:00
committed by David Sterba
parent c36cac28cb
commit c7333972b9
2 changed files with 30 additions and 8 deletions
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5
fs/btrfs/extent_io.h
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@@ -312,8 +312,9 @@ struct io_failure_record {
};
bool btrfs_check_repairable(struct inode *inode, unsigned failed_bio_pages,
struct io_failure_record *failrec, int fail_mirror);
bool btrfs_check_repairable(struct inode *inode, bool needs_validation,
struct io_failure_record *failrec,
int failed_mirror);
struct bio *btrfs_create_repair_bio(struct inode *inode, struct bio *failed_bio,
struct io_failure_record *failrec,
struct page *page, int pg_offset, int icsum,