Re: Kernel crash in icq_free_icq_rcu

[Tejun Heo <tj@kernel.org>]

On Tue, Jan 17, 2012 at 03:18:23PM -0500, Vivek Goyal wrote:
> Hi Tejun,
> 
> With latest linus kernel, I see following crash. I was running some
> scripts which create cgroups and launch fio jobs in those groups. In
> a separate window I wrote a script to change the IO scheduler on the
> device in a loop while IO was happening on the device. After few
> seconds I see following. So far I tried it twice and reproduced it
> both the times in first few seconds.

Does the following patch make any difference?

diff --git a/block/elevator.c b/block/elevator.c
index 91e18f8..b5a94ed 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -105,6 +105,7 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (bio_integrity(bio) != blk_integrity_rq(rq))
 		return 0;
 
+	return 0;
 	if (!elv_iosched_allow_merge(rq, bio))
 		return 0;