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>

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 2ee5e357a0a717acf94defdd4fa335a0a49d14b1..07cfef67c0bab35fa83d7b1dd0e76b579b2dc334 100644 (file)
--- 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);
 }
 

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index b66745bd08bbcc2dd1ab349f47c7326199518778..5f7063f05ae0771e3a8ebaaf697da58b9d4308d5 100644 (file)
--- 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;
                }

diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 314d17ca64668a70ea1f6445111ca19b2024141e..64dd0b34fcf490cee3779e179e9b8c7c543b7e53 100644 (file)
--- 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 b0672756d0562697238cb9cf53775c3c48d87a4a..e1f51d607cc541924cc54c43aaa7b80c06a6322e 100644 (file)
--- 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: