From 645efa84f6c7566ea863ed37a8b3247247f72e02 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Tue, 5 Feb 2019 05:09:00 -0500 Subject: [PATCH 1/2] dm: add memory barrier before waitqueue_active Block core changes to switch bio-based IO accounting to be percpu had a side-effect of altering DM core to now rely on calling waitqueue_active (in both bio-based and request-based) to check if another task is in dm_wait_for_completion(). A memory barrier is needed before calling waitqueue_active(). DM core doesn't piggyback on a preceding memory barrier so it must explicitly use its own. For more details on why using waitqueue_active() without a preceding barrier is unsafe, please see the comment before the waitqueue_active() definition in include/linux/wait.h. Add the missing memory barrier by switching to using wq_has_sleeper(). Fixes: 6f75723190d8 ("dm: remove the pending IO accounting") Fixes: c4576aed8d85 ("dm: fix request-based dm's use of dm_wait_for_completion") Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer --- drivers/md/dm-rq.c | 2 +- drivers/md/dm.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 4eb5f8c56535..a20531e5f3b4 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -131,7 +131,7 @@ static void rq_end_stats(struct mapped_device *md, struct request *orig) static void rq_completed(struct mapped_device *md) { /* nudge anyone waiting on suspend queue */ - if (unlikely(waitqueue_active(&md->wait))) + if (unlikely(wq_has_sleeper(&md->wait))) wake_up(&md->wait); /* diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 2b53c3841b53..a0972a9301de 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -699,7 +699,7 @@ static void end_io_acct(struct dm_io *io) true, duration, &io->stats_aux); /* nudge anyone waiting on suspend queue */ - if (unlikely(waitqueue_active(&md->wait))) + if (unlikely(wq_has_sleeper(&md->wait))) wake_up(&md->wait); } From fa8db4948f5224dae33a0e783e7dec682e145f88 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Tue, 5 Feb 2019 17:07:58 -0500 Subject: [PATCH 2/2] dm: don't use bio_trim() afterall bio_trim() has an early return, which makes it _not_ idempotent, if the offset is 0 and the bio's bi_size already matches the requested size. Prior to DM, all users of bio_trim() were fine with this. But DM has exposed the fact that bio_trim()'s early return is incompatible with a cloned bio whose integrity payload must be trimmed via bio_integrity_trim(). Fix this by reverting DM back to doing the equivalent of bio_trim() but in an idempotent manner (so bio_integrity_trim is always performed). Follow-on work is needed to assess what benefit bio_trim()'s early return is providing to its existing callers. Reported-by: Milan Broz Fixes: 57c36519e4b94 ("dm: fix clone_bio() to trigger blk_recount_segments()") Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index a0972a9301de..515e6af9bed2 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1336,7 +1336,11 @@ static int clone_bio(struct dm_target_io *tio, struct bio *bio, return r; } - bio_trim(clone, sector - clone->bi_iter.bi_sector, len); + bio_advance(clone, to_bytes(sector - clone->bi_iter.bi_sector)); + clone->bi_iter.bi_size = to_bytes(len); + + if (bio_integrity(bio)) + bio_integrity_trim(clone); return 0; }