Messages in this thread Patch in this message | | | From | Dmitry Monakhov <> | Subject | Re: CFQ is broken for CONFIG_BLK_CGROUP=y, CFQ_GROUP_IOSCHED=n | Date | Wed, 28 Apr 2010 19:36:02 +0400 |
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Vivek Goyal <vgoyal@redhat.com> writes:
> On Wed, Apr 28, 2010 at 04:44:51PM +0400, Dmitry Monakhov wrote: >> >> I've had an oops on kernel boot due to NULL pointer deference >> linux-2.6-block/for-next HEAD:7eaed1226ab411ee5dc8c34fc0d8034e4c98e3c6 >> I've enabled CONFIG_BLK_CGROUP, but not CFQ_GROUP_IOSCHED >> In this case cfq_ref_get_cfqg() defined as >> static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg) >> { >> return NULL; >> } >> So following call trace is simply NOOP >> cfq_set_request() >> rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg); >> >> Which later result in OOPS on bio insertion >> cfq_insert_request >> -> blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,...) >> -> spin_lock_irqsave(&blkg->stats_lock, flags); >> >> Bad commit. >> >From 7f1dc8a2d2f45fc557b27fd56115338b1d34fc24 Mon Sep 17 00:00:00 2001 >> From: Vivek Goyal <vgoyal@redhat.com> >> Date: Wed, 21 Apr 2010 17:44:16 +0200 >> Subject: [PATCH] blkio: Fix blkio crash during rq stat update > > Dmitry, this patch should fix the issue. Can you please give it a try. Yes. the issue is gone. > > Jens, I know you don't like this form of cfq_ref_get_cfqg(), but this > seems to be the simplest solution to fix it. IMHO following fix is simpler, and cleaner. diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 286008c..0f3eb70 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1094,7 +1094,7 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create) static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg) { - return NULL; + return cfqg; } static inline void | |