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authorRoland Dreier2012-11-22 04:00:11 -0600
committerJens Axboe2012-11-23 07:32:55 -0600
commit893d290f1d7496db97c9471bc352ad4a11dc8a25 (patch)
treec6d5444d06949edfd5d13fa0beed0992dd2ae469 /block/blk-exec.c
parent836413e8c78ecbc55aa31f3cb600f8ee1aa355a2 (diff)
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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>
Diffstat (limited to 'block/blk-exec.c')
-rw-r--r--block/blk-exec.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/block/blk-exec.c b/block/blk-exec.c
index 8b6dc5bd4dd..f71eac35c1b 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,
52 rq_end_io_fn *done) 52 rq_end_io_fn *done)
53{ 53{
54 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; 54 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
55 bool is_pm_resume;
55 56
56 WARN_ON(irqs_disabled()); 57 WARN_ON(irqs_disabled());
57 58
58 rq->rq_disk = bd_disk; 59 rq->rq_disk = bd_disk;
59 rq->end_io = done; 60 rq->end_io = done;
61 /*
62 * need to check this before __blk_run_queue(), because rq can
63 * be freed before that returns.
64 */
65 is_pm_resume = rq->cmd_type == REQ_TYPE_PM_RESUME;
60 66
61 spin_lock_irq(q->queue_lock); 67 spin_lock_irq(q->queue_lock);
62 68
@@ -71,7 +77,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
71 __elv_add_request(q, rq, where); 77 __elv_add_request(q, rq, where);
72 __blk_run_queue(q); 78 __blk_run_queue(q);
73 /* the queue is stopped so it won't be run */ 79 /* the queue is stopped so it won't be run */
74 if (rq->cmd_type == REQ_TYPE_PM_RESUME) 80 if (is_pm_resume)
75 q->request_fn(q); 81 q->request_fn(q);
76 spin_unlock_irq(q->queue_lock); 82 spin_unlock_irq(q->queue_lock);
77} 83}