From 985eabdcfe3aad1aea6fc195dafff503f303aa3a Mon Sep 17 00:00:00 2001 From: Jeffle Xu Date: Wed, 4 Nov 2020 11:57:56 +0800 Subject: [PATCH] dm: remove unnecessary current->bio_list check when submitting split bio The depth-first splitting is introduced in commit 18a25da84354 ("dm: ensure bio submission follows a depth-first tree walk"), which is used to fix the potential deadlock in case of the misordering handling of bios caused by bio_list. There're two paths submitting split bios, dm_wq_work() from worker thread and submit_bio() from application. Back upon that time, dm_wq_work() thread calls __split_and_process_bio() directly and thus will not trigger this issue since bio_list doesn't exist here. So this issue will only be triggered from application calling submit_bio(), and the fix has to check if current->bio_list is non-NULL to distinguish this case. However since commit 0c2915b8c6db1 ("dm: fix missing imposition of queue_limits from dm_wq_work() thread"), dm_wq_work() thread calls submit_bio_noacct() and thus also uses bio_list. Since then all entries into __split_and_process_bio() are under protection of bio_list, and thus the checking of current->bio_list when determinning if the depth-first principle should be used, seems kind of nonsense. After all the checking always succeeds now. Fixes: 0c2915b8c6db1 ("dm: fix missing imposition of queue_limits from dm_wq_work() thread") Signed-off-by: Jeffle Xu Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 4e0cbfe..9408df4 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1590,7 +1590,7 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md, ci.sector_count = bio_sectors(bio); while (ci.sector_count && !error) { error = __split_and_process_non_flush(&ci); - if (current->bio_list && ci.sector_count && !error) { + if (ci.sector_count && !error) { /* * Remainder must be passed to submit_bio_noacct() * so that it gets handled *after* bios already submitted -- 2.7.4