dm rq: don't queue request to blk-mq during DM suspend

DM uses blk-mq's quiesce/unquiesce to stop/start device mapper queue.

But blk-mq's unquiesce may come from outside events, such as elevator
switch, updating nr_requests or others, and request may come during
suspend, so simply ask for blk-mq to requeue it.

Fixes one kernel panic issue when running updating nr_requests and
dm-mpath suspend/resume stress test.

Cc: stable@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 5b95eea..a896dea 100644 (file)
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -490,6 +490,14 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
        struct mapped_device *md = tio->md;
        struct dm_target *ti = md->immutable_target;
 
+       /*
+        * blk-mq's unquiesce may come from outside events, such as
+        * elevator switch, updating nr_requests or others, and request may
+        * come during suspend, so simply ask for blk-mq to requeue it.
+        */
+       if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)))
+               return BLK_STS_RESOURCE;
+
        if (unlikely(!ti)) {
                int srcu_idx;
                struct dm_table *map = dm_get_live_table(md, &srcu_idx);