3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Roland Dreier <rol...@purestorage.com>
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 <rol...@purestorage.com>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
block/blk-exec.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -49,6 +49,7 @@ void blk_execute_rq_nowait(struct reques
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 reques
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);
}
--
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