[PATCH 4.19 126/190] dm mpath: fix missing call of path selector type->end_io

Greg Kroah-Hartman
2019-09-13T13:17:11Z

[ Upstream commit 5de719e3d01b4abe0de0d7b857148a880ff2a90b ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/dm-mpath.c | 17 ++++++++++++++++-
drivers/md/dm-rq.c | 8 ++++----
drivers/md/dm-target.c | 3 ++-
include/linux/device-mapper.h | 3 ++-
4 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index baa966e2778c0..481e54ded9dc7 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -554,8 +554,23 @@ 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);
}

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 264b84e274aac..17c6a73c536c6 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -219,7 +219,7 @@ 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);
if (!rq->q->mq_ops)
@@ -270,7 +270,7 @@ 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);
}

if (!rq->q->mq_ops)
@@ -495,7 +495,7 @@ check_again:
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;
}

@@ -505,7 +505,7 @@ check_again:
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;
if (!rq->q->mq_ops)
r = DM_MAPIO_DELAY_REQUEUE;
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 314d17ca64668..64dd0b34fcf49 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -136,7 +136,8 @@ static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
return DM_MAPIO_KILL;
}

-static void io_err_release_clone_rq(struct request *clone)
+static void io_err_release_clone_rq(struct request *clone,
+ union map_info *map_context)
{
}

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index bef2e36c01b4b..91f9f95ad5066 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -62,7 +62,8 @@ typedef int (*dm_clone_and_map_request_fn) (struct dm_target *ti,
struct request *rq,
union map_info *map_context,
struct request **clone);
-typedef void (*dm_release_clone_request_fn) (struct request *clone);
+typedef void (*dm_release_clone_request_fn) (struct request *clone,
+ union map_info *map_context);

/*
* Returns:
--
2.20.1