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Commit 06eb061f authored by Bart Van Assche's avatar Bart Van Assche Committed by Mike Snitzer
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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: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 117aceb0

drivers/md/dm-mpath.c

+2 −3
Original line number Diff line number Diff line
@@ -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;

drivers/md/dm-rq.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}