Mike Snitzer 3d9f39d274 dm: fix bio splitting and its bio completion order for regular IO
commit ee1dfad5325ff1cfb2239e564cd411b3bfe8667a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-10-01 13:18:25 +02:00
..
2019-09-16 10:18:01 -04:00
2019-09-04 09:39:22 -04:00
2019-08-23 10:13:12 -04:00
2019-09-12 09:32:31 -04:00
2019-09-12 09:32:31 -04:00
2019-03-12 10:15:18 -07:00