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| author | Roland Dreier <roland@purestorage.com> | 2012-11-22 02:00:11 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2012-12-06 11:20:35 +0000 |
| commit | 32eb44e290d1151e9eb26f57564dae6966190685 (patch) | |
| tree | add2e86801ceab4d9fd8fd543e240c0ec7e98a71 /block | |
| parent | de268a9f92b3b2504e9f87db3b4dd609aafb255f (diff) | |
| download | lwn-32eb44e290d1151e9eb26f57564dae6966190685.tar.gz lwn-32eb44e290d1151e9eb26f57564dae6966190685.zip | |
block: Don't access request after it might be freed
commit 893d290f1d7496db97c9471bc352ad4a11dc8a25 upstream.
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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-exec.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/block/blk-exec.c b/block/blk-exec.c index 60532852b3ab..ac2c6e7f0538 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -49,6 +49,7 @@ 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; if (unlikely(blk_queue_dead(q))) { rq->errors = -ENXIO; @@ -59,12 +60,18 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, 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; + WARN_ON(irqs_disabled()); spin_lock_irq(q->queue_lock); __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); } |