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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: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Bart Van Assche 2017-04-07 16:50:44 -07:00 committed by Mike Snitzer
parent 117aceb030
commit 06eb061f48
2 changed files with 3 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/md/dm-mpath.c
View File

@ -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;

2
drivers/md/dm-rq.c
View File

@ -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);
}