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, 16 insertions, 1 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 2ee5e357a0a7..07cfef67c0ba 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -544,8 +544,23 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 	return DM_MAPIO_REMAPPED;
 }
 
-static void multipath_release_clone(struct request *clone)
+static void multipath_release_clone(struct request *clone,
+				    union map_info *map_context)
 {
+	if (unlikely(map_context)) {
+		/*
+		 * non-NULL map_context means caller is still map
+		 * method; must undo multipath_clone_and_map()
+		 */
+		struct dm_mpath_io *mpio = get_mpio(map_context);
+		struct pgpath *pgpath = mpio->pgpath;
+
+		if (pgpath && pgpath->pg->ps.type->end_io)
+			pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
+						    &pgpath->path,
+						    mpio->nr_bytes);
+	}
+
 	blk_put_request(clone);
 }