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| author | Mike Snitzer <snitzer@redhat.com> | 2015-04-29 10:48:09 -0400 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-04-30 10:25:21 -0400 |
| commit | aa6df8dd28c01d9a3d2cfcfe9dd0a4a334d1cd81 (patch) | |
| tree | 80ee42fd298572758a252c8024e1dcc2e11f58a2 /drivers | |
| parent | 3e6180f0c82b3790a9ec6d13d67aae359bf1ce84 (diff) | |
| download | lwn-aa6df8dd28c01d9a3d2cfcfe9dd0a4a334d1cd81.tar.gz lwn-aa6df8dd28c01d9a3d2cfcfe9dd0a4a334d1cd81.zip | |
dm: fix free_rq_clone() NULL pointer when requeueing unmapped request
Commit 022333427a ("dm: optimize dm_mq_queue_rq to _not_ use kthread if
using pure blk-mq") mistakenly removed free_rq_clone()'s clone->q check
before testing clone->q->mq_ops. It was an oversight to discontinue
that check for 1 of the 2 use-cases for free_rq_clone():
1) free_rq_clone() called when an unmapped original request is requeued
2) free_rq_clone() called in the request-based IO completion path
The clone->q check made sense for case #1 but not for #2. However, we
cannot just reinstate the check as it'd mask a serious bug in the IO
completion case #2 -- no in-flight request should have an uninitialized
request_queue (basic block layer refcounting _should_ ensure this).
The NULL pointer seen for case #1 is detailed here:
https://www.redhat.com/archives/dm-devel/2015-April/msg00160.html
Fix this free_rq_clone() NULL pointer by simply checking if the
mapped_device's type is DM_TYPE_MQ_REQUEST_BASED (clone's queue is
blk-mq) rather than checking clone->q->mq_ops. This avoids the need to
dereference clone->q, but a WARN_ON_ONCE is added to let us know if an
uninitialized clone request is being completed.
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/md/dm.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 923496ba72a0..a930b72314ac 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1082,18 +1082,26 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue) dm_put(md); } -static void free_rq_clone(struct request *clone) +static void free_rq_clone(struct request *clone, bool must_be_mapped) { struct dm_rq_target_io *tio = clone->end_io_data; struct mapped_device *md = tio->md; + WARN_ON_ONCE(must_be_mapped && !clone->q); + blk_rq_unprep_clone(clone); - if (clone->q->mq_ops) + if (md->type == DM_TYPE_MQ_REQUEST_BASED) + /* stacked on blk-mq queue(s) */ tio->ti->type->release_clone_rq(clone); else if (!md->queue->mq_ops) /* request_fn queue stacked on request_fn queue(s) */ free_clone_request(md, clone); + /* + * NOTE: for the blk-mq queue stacked on request_fn queue(s) case: + * no need to call free_clone_request() because we leverage blk-mq by + * allocating the clone at the end of the blk-mq pdu (see: clone_rq) + */ if (!md->queue->mq_ops) free_rq_tio(tio); @@ -1124,7 +1132,7 @@ static void dm_end_request(struct request *clone, int error) rq->sense_len = clone->sense_len; } - free_rq_clone(clone); + free_rq_clone(clone, true); if (!rq->q->mq_ops) blk_end_request_all(rq, error); else @@ -1143,7 +1151,7 @@ static void dm_unprep_request(struct request *rq) } if (clone) - free_rq_clone(clone); + free_rq_clone(clone, false); } /* |