dm mpath: fix missing call of path selector type->end_io

After commit 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging via
blk_insert_cloned_request feedback"), map_request() will requeue the tio
when issued clone request return BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE.

Thus, if device driver status is error, a tio may be requeued multiple
times until the return value is not DM_MAPIO_REQUEUE.  That means
type->start_io may be called multiple times, while type->end_io is only
called when IO complete.

In fact, even without commit 396eaf21ee17, setup_clone() failure can
also cause tio requeue and associated missed call to type->end_io.

The service-time path selector selects path based on in_flight_size,
which is increased by st_start_io() and decreased by st_end_io().
Missed calls to st_end_io() can lead to in_flight_size count error and
will cause the selector to make the wrong choice.  In addition,
queue-length path selector will also be affected.

To fix the problem, call type->end_io in ->release_clone_rq before tio
requeue.  map_info is passed to ->release_clone_rq() for map_request()
error path that result in requeue.

Fixes: 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging via blk_insert_cloned_request feedback")
Cc: stable@vger.kernl.org
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index b66745bd08bb..5f7063f05ae0 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -168,7 +168,7 @@ static void dm_end_request(struct request *clone, blk_status_t error)
 	struct request *rq = tio->orig;
 
 	blk_rq_unprep_clone(clone);
-	tio->ti->type->release_clone_rq(clone);
+	tio->ti->type->release_clone_rq(clone, NULL);
 
 	rq_end_stats(md, rq);
 	blk_mq_end_request(rq, error);
@@ -201,7 +201,7 @@ static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool delay_
 	rq_end_stats(md, rq);
 	if (tio->clone) {
 		blk_rq_unprep_clone(tio->clone);
-		tio->ti->type->release_clone_rq(tio->clone);
+		tio->ti->type->release_clone_rq(tio->clone, NULL);
 	}
 
 	dm_mq_delay_requeue_request(rq, delay_ms);
@@ -398,7 +398,7 @@ static int map_request(struct dm_rq_target_io *tio)
 	case DM_MAPIO_REMAPPED:
 		if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
 			/* -ENOMEM */
-			ti->type->release_clone_rq(clone);
+			ti->type->release_clone_rq(clone, &tio->info);
 			return DM_MAPIO_REQUEUE;
 		}
 
@@ -408,7 +408,7 @@ static int map_request(struct dm_rq_target_io *tio)
 		ret = dm_dispatch_clone_request(clone, rq);
 		if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
 			blk_rq_unprep_clone(clone);
-			tio->ti->type->release_clone_rq(clone);
+			tio->ti->type->release_clone_rq(clone, &tio->info);
 			tio->clone = NULL;
 			return DM_MAPIO_REQUEUE;
 		}