[PATCH] CFQ io scheduler: scheduler switch oops
If cfq is managing a queue and a new scheduler is later selected, it is
possible for the cfqd unplug_work work to be queued after the kblockd
work struct has been flushed. The problem is the ordering of
cfq_shutdown_timer_wq() and blk_put_queue() in cfq_put_cfqd(). The
latter may rearm the work, leaving cfq_kick_queue() with dead data.
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/block/cfq-iosched.c b/drivers/block/cfq-iosched.c
index 1ecb179..ff1cc96 100644
--- a/drivers/block/cfq-iosched.c
+++ b/drivers/block/cfq-iosched.c
@@ -2249,10 +2249,11 @@
if (!atomic_dec_and_test(&cfqd->ref))
return;
- cfq_shutdown_timer_wq(cfqd);
-
blk_put_queue(q);
+ cfq_shutdown_timer_wq(cfqd);
+ q->elevator->elevator_data = NULL;
+
mempool_destroy(cfqd->crq_pool);
kfree(cfqd->crq_hash);
kfree(cfqd->cfq_hash);