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

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After commit 396eaf21ee ("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 396eaf21ee, 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: 396eaf21ee ("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>
This commit is contained in:
Yufen Yu
2019-04-24 23:19:05 +08:00
committed by Mike Snitzer
parent 873f258bec
commit 5de719e3d0
4 changed files with 24 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/md/dm-rq.c
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@@ -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;
}