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| author |   Mike Snitzer <snitzer@redhat.com> | 2020-09-14 13:04:19 -0400 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2020-09-21 19:42:20 -0400 |
| commit | ee1dfad5325ff1cfb2239e564cd411b3bfe8667a (patch) | |
| tree | b585d0089216ae7feab34157b8432ae0edf3fa71 /drivers | |
| parent | Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm (diff) | |
| download | linux-dev-ee1dfad5325ff1cfb2239e564cd411b3bfe8667a.tar.xz linux-dev-ee1dfad5325ff1cfb2239e564cd411b3bfe8667a.zip | |
dm: fix bio splitting and its bio completion order for regular IO
dm_queue_split() is removed because __split_and_process_bio() _must_
handle splitting bios to ensure proper bio submission and completion
ordering as a bio is split.
Otherwise, multiple recursive calls to ->submit_bio will cause multiple
split bios to be allocated from the same ->bio_split mempool at the same
time. This would result in deadlock in low memory conditions because no
progress could be made (only one bio is available in ->bio_split
mempool).
This fix has been verified to still fix the loss of performance, due
to excess splitting, that commit 120c9257f5f1 provided.
Fixes: 120c9257f5f1 ("Revert "dm: always call blk_queue_split() in dm_process_bio()"")
Cc: stable@vger.kernel.org # 5.0+, requires custom backport due to 5.9 changes
Reported-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/md/dm.c | 23 |
1 files changed, 2 insertions, 21 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 4a40df8af7d3..d948cd522431 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1724,23 +1724,6 @@ out: return ret; } -static void dm_queue_split(struct mapped_device *md, struct dm_target *ti, struct bio **bio) -{ - unsigned len, sector_count; - - sector_count = bio_sectors(*bio); - len = min_t(sector_t, max_io_len((*bio)->bi_iter.bi_sector, ti), sector_count); - - if (sector_count > len) { - struct bio *split = bio_split(*bio, len, GFP_NOIO, &md->queue->bio_split); - - bio_chain(split, *bio); - trace_block_split(md->queue, split, (*bio)->bi_iter.bi_sector); - submit_bio_noacct(*bio); - *bio = split; - } -} - static blk_qc_t dm_process_bio(struct mapped_device *md, struct dm_table *map, struct bio *bio) { @@ -1768,14 +1751,12 @@ static blk_qc_t dm_process_bio(struct mapped_device *md, if (current->bio_list) { if (is_abnormal_io(bio)) blk_queue_split(&bio); - else - dm_queue_split(md, ti, &bio); + /* regular IO is split by __split_and_process_bio */ } if (dm_get_md_type(md) == DM_TYPE_NVME_BIO_BASED) return __process_bio(md, map, bio, ti); - else - return __split_and_process_bio(md, map, bio); + return __split_and_process_bio(md, map, bio); } static blk_qc_t dm_submit_bio(struct bio *bio) |