Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755371Ab0D1PgK (ORCPT ); Wed, 28 Apr 2010 11:36:10 -0400 Received: from mail-bw0-f219.google.com ([209.85.218.219]:45249 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753245Ab0D1PgH (ORCPT ); Wed, 28 Apr 2010 11:36:07 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:from:to:cc:subject:references:date:in-reply-to:message-id :user-agent:mime-version:content-type; b=fndL1CEvL2S0dvvdTIj/TcpfyzKzB1DJ9XnCh9i5MTQtOJGfajkH0wu/t8AGSqZ7Vo YtdSUKWT+yRCA5X/OUPLizWwDEVYhnQNcRSRoFLJNc5IMgRYNScJChTdmKHgKBPuX7SB 7ymo8fD6d+wWpvxtgq5nMjP7DvcXJNHEqd+3s= From: Dmitry Monakhov To: Vivek Goyal Cc: linux-kernel@vger.kernel.org, jens.axboe@oracle.com Subject: Re: CFQ is broken for CONFIG_BLK_CGROUP=y, CFQ_GROUP_IOSCHED=n References: <877hnrg30c.fsf@openvz.org> <20100428150959.GA16033@redhat.com> Date: Wed, 28 Apr 2010 19:36:02 +0400 In-Reply-To: <20100428150959.GA16033@redhat.com> (Vivek Goyal's message of "Wed, 28 Apr 2010 11:09:59 -0400") Message-ID: <87ljc7egil.fsf@openvz.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=-=-=" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1969 Lines: 59 --=-=-= Vivek Goyal 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 >> 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. --=-=-= Content-Disposition: inline; filename=diff 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 --=-=-=-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/