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block: Don't access request after it might be freed

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commit 893d290f1d 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>
[xr: Backported to 3.4: adjust context]
Signed-off-by: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Roland Dreier 2012-11-22 02:00:11 -08:00 committed by Greg Kroah-Hartman
parent 50e97121b7
commit 0ef4c881e4
1 changed files with 11 additions and 1 deletions
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12
block/blk-exec.c
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@ -49,8 +49,18 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
rq_end_io_fn *done) rq_end_io_fn *done)
{ {
int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
bool is_pm_resume;
WARN_ON(irqs_disabled()); 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); spin_lock_irq(q->queue_lock);
if (unlikely(blk_queue_dead(q))) { if (unlikely(blk_queue_dead(q))) {
@ -66,7 +76,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
__elv_add_request(q, rq, where); __elv_add_request(q, rq, where);
__blk_run_queue(q); __blk_run_queue(q);
/* the queue is stopped so it won't be run */ /* 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); q->request_fn(q);
spin_unlock_irq(q->queue_lock); spin_unlock_irq(q->queue_lock);
} }