diff options
author | Roland Dreier <roland@purestorage.com> | 2012-11-22 14:00:11 +0400 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2012-11-23 17:32:55 +0400 |
commit | 893d290f1d7496db97c9471bc352ad4a11dc8a25 (patch) | |
tree | c6d5444d06949edfd5d13fa0beed0992dd2ae469 | |
parent | 836413e8c78ecbc55aa31f3cb600f8ee1aa355a2 (diff) |
block: Don't access request after it might be freed
After we've done __elv_add_request() and __blk_run_queue() in
blk_execute_rq_nowait(), the request might finish and be freed
immediately. Therefore checking if the type is REQ_TYPE_PM_RESUME
isn't safe afterwards, because if it isn't, rq might be gone.
Instead, check beforehand and stash the result in a temporary.
This fixes crashes in blk_execute_rq_nowait() I get occasionally when
running with lots of memory debugging options enabled -- I think this
race is usually harmless because the window for rq to be reallocated
is so small.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r-- | block/blk-exec.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/block/blk-exec.c b/block/blk-exec.c index 8b6dc5bd4dd0..f71eac35c1b9 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -52,11 +52,17 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, rq_end_io_fn *done) { int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; + bool is_pm_resume; WARN_ON(irqs_disabled()); rq->rq_disk = bd_disk; rq->end_io = done; + /* + * need to check this before __blk_run_queue(), because rq can + * be freed before that returns. + */ + is_pm_resume = rq->cmd_type == REQ_TYPE_PM_RESUME; spin_lock_irq(q->queue_lock); @@ -71,7 +77,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, __elv_add_request(q, rq, where); __blk_run_queue(q); /* the queue is stopped so it won't be run */ - if (rq->cmd_type == REQ_TYPE_PM_RESUME) + if (is_pm_resume) q->request_fn(q); spin_unlock_irq(q->queue_lock); } |