From 06eb061f48594aa369f6e852b352410298b317a8 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 7 Apr 2017 16:50:44 -0700 Subject: [PATCH] dm mpath: requeue after a small delay if blk_get_request() fails If blk_get_request() returns ENODEV then multipath_clone_and_map() causes a request to be requeued immediately. This can cause a kworker thread to spend 100% of the CPU time of a single core in __blk_mq_run_hw_queue() and also can cause device removal to never finish. Avoid this by only requeuing after a delay if blk_get_request() fails. Additionally, reduce the requeue delay. Cc: stable@vger.kernel.org # 4.9+ Signed-off-by: Bart Van Assche Signed-off-by: Mike Snitzer --- drivers/md/dm-mpath.c | 5 ++--- drivers/md/dm-rq.c | 2 +- 2 files changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 7f223dbed49f..a4cc4d42117b 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -484,7 +484,6 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq, struct request **__clone) { struct multipath *m = ti->private; - int r = DM_MAPIO_REQUEUE; size_t nr_bytes = blk_rq_bytes(rq); struct pgpath *pgpath; struct block_device *bdev; @@ -503,7 +502,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq, } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) { pg_init_all_paths(m); - return r; + return DM_MAPIO_REQUEUE; } memset(mpio, 0, sizeof(*mpio)); @@ -517,7 +516,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq, GFP_ATOMIC); if (IS_ERR(clone)) { /* EBUSY, ENODEV or EWOULDBLOCK: requeue */ - return r; + return DM_MAPIO_DELAY_REQUEUE; } clone->bio = clone->biotail = NULL; clone->rq_disk = bdev->bd_disk; diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 28955b94d2b2..90756a56c4d3 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -280,7 +280,7 @@ static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool delay_ if (!rq->q->mq_ops) dm_old_requeue_request(rq); else - dm_mq_delay_requeue_request(rq, delay_requeue ? 5000 : 0); + dm_mq_delay_requeue_request(rq, delay_requeue ? 100/*ms*/ : 0); rq_completed(md, rw, false); }