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| author |   Ming Lei <ming.lei@redhat.com> | 2022-06-23 21:20:05 +0800 |
|---|---|---|
| committer |   Mike Snitzer <snitzer@kernel.org> | 2022-06-23 14:33:13 -0400 |
| commit | 61b6e2e5321da281ab3c0c04e1962b3d000f6248 (patch) | |
| tree | 0e3d4eb1c7d51ca0b95232075b68b2ddb4b13760 /drivers/md/dm-core.h | |
| parent | dm: do not return early from dm_io_complete if BLK_STS_AGAIN without polling (diff) | |
| download | linux-dev-61b6e2e5321da281ab3c0c04e1962b3d000f6248.tar.xz linux-dev-61b6e2e5321da281ab3c0c04e1962b3d000f6248.zip | |
dm: fix BLK_STS_DM_REQUEUE handling when dm_io represents split bio
Commit 7dd76d1feec7 ("dm: improve bio splitting and associated IO
accounting") removed using cloned bio when dm io splitting is needed.
Using bio_trim()+bio_inc_remaining() rather than bio_split()+bio_chain()
causes multiple dm_io instances to share the same original bio, and it
works fine if IOs are completed successfully.
But a regression was caused for the case when BLK_STS_DM_REQUEUE is
returned from any one of DM's cloned bios (whose dm_io share the same
orig_bio). In this BLK_STS_DM_REQUEUE case only the mapped subset of
the original bio for the current exact dm_io needs to be re-submitted.
However, since the original bio is shared among all dm_io instances,
the ->orig_bio actually only represents the last dm_io instance, so
requeue can't work as expected. Also when more than one dm_io is
requeued, the same original bio is requeued from all dm_io's
completion handler, then race is caused.
Fix this issue by still allocating one clone bio for completing io
only, then io accounting can rely on ->orig_bio being unmodified. This
is needed because the dm_io's sector_offset and sectors members are
recorded relative to an unmodified ->orig_bio.
In the future, we can go back to using bio_trim()+bio_inc_remaining()
for dm's io splitting but then delay needing a bio clone only when
handling BLK_STS_DM_REQUEUE, but that approach is a bit complicated
(so it needs a development cycle):
1) bio clone needs to be done in task context
2) a block interface for unwinding bio is required
Fixes: 7dd76d1feec7 ("dm: improve bio splitting and associated IO accounting")
Reported-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers/md/dm-core.h')
| -rw-r--r-- | drivers/md/dm-core.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 54c0473a51dd..c954ff91870e 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -272,6 +272,7 @@ struct dm_io { atomic_t io_count; struct mapped_device *md; + struct bio *split_bio; /* The three fields represent mapped part of original bio */ struct bio *orig_bio; unsigned int sector_offset; /* offset to end of orig_bio */ |