diff options
authorTejun Heo <>2011-11-03 18:52:11 +0100
committerJens Axboe <>2011-11-03 18:52:11 +0100
commit6dd9ad7df2019b1e33a372a501907db293ebcd0d (patch)
parent334c2b0b8b2ab186fa198413386cba41fffcb4f2 (diff)
block: don't call blk_drain_queue() if elevator is not upfor-3.2/core
blk_cleanup_queue() may be called before elevator is set up on a queue which triggers the following oops. BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8125a69c>] elv_drain_elevator+0x1c/0x70 ... Pid: 830, comm: kworker/0:2 Not tainted 3.1.0-next-20111025_64+ #1590 Bochs Bochs RIP: 0010:[<ffffffff8125a69c>] [<ffffffff8125a69c>] elv_drain_elevator+0x1c/0x70 ... Call Trace: [<ffffffff8125da92>] blk_drain_queue+0x42/0x70 [<ffffffff8125db90>] blk_cleanup_queue+0xd0/0x1c0 [<ffffffff81469640>] md_free+0x50/0x70 [<ffffffff8126f43b>] kobject_release+0x8b/0x1d0 [<ffffffff81270d56>] kref_put+0x36/0xa0 [<ffffffff8126f2b7>] kobject_put+0x27/0x60 [<ffffffff814693af>] mddev_delayed_delete+0x2f/0x40 [<ffffffff81083450>] process_one_work+0x100/0x3b0 [<ffffffff8108527f>] worker_thread+0x15f/0x3a0 [<ffffffff81089937>] kthread+0x87/0x90 [<ffffffff81621834>] kernel_thread_helper+0x4/0x10 Fix it by making blk_cleanup_queue() check whether q->elevator is set up before invoking blk_drain_queue. Signed-off-by: Tejun Heo <> Reported-and-tested-by: Jiri Slaby <> Signed-off-by: Jens Axboe <>
1 files changed, 7 insertions, 2 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index f65871116404..f43c8a5840ae 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -407,8 +407,13 @@ void blk_cleanup_queue(struct request_queue *q)
- /* drain all requests queued before DEAD marking */
- blk_drain_queue(q, true);
+ /*
+ * Drain all requests queued before DEAD marking. The caller might
+ * be trying to tear down @q before its elevator is initialized, in
+ * which case we don't want to call into draining.
+ */
+ if (q->elevator)
+ blk_drain_queue(q, true);
/* @q won't process any more request, flush async actions */