From: Roland Dreier <roland@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
[xr: Backported to 3.4: adjust context]
Signed-off-by: Rui Xiang <rui.xiang@xxxxxxxxxx>
---
block/blk-exec.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/block/blk-exec.c b/block/blk-exec.c
index fb2cbd5..1b5cb66 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -49,8 +49,18 @@ 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);
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);
__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);
}
--
1.8.2.2
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