From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751353Ab1AEOAx (ORCPT ); Wed, 5 Jan 2011 09:00:53 -0500 Received: from mx2.fusionio.com ([64.244.102.31]:48283 "EHLO mx2.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751184Ab1AEOAw (ORCPT ); Wed, 5 Jan 2011 09:00:52 -0500 X-ASG-Debug-ID: 1294236042-71f760180001-xx1T2L X-Barracuda-Envelope-From: JAxboe@fusionio.com Message-ID: <4D247984.2030103@fusionio.com> Date: Wed, 5 Jan 2011 15:00:36 +0100 From: Jens Axboe MIME-Version: 1.0 To: Jerome Marchand CC: Vivek Goyal , Satoru Takeuchi , Linus Torvalds , Yasuaki Ishimatsu , "linux-kernel@vger.kernel.org" , Greg Kroah-Hartman Subject: Re: [PATCH 2/2] block: fix accounting bug on cross partition merges References: <4CFF3DA4.5060705@jp.fujitsu.com> <4CFF9A2C.1070401@fusionio.com> <4D025154.8030400@redhat.com> <20101210165553.GE31737@redhat.com> <4D07D2AC.6000500@fusionio.com> <4D0B68AF.80804@redhat.com> <4D0BB4A1.8080305@fusionio.com> <4D13664C.3020500@redhat.com> <20101223153915.GE9502@redhat.com> <4D13810B.8000304@redhat.com> <20101224192916.GB2082@redhat.com> <4D23423A.60707@redhat.com> <4D2342E1.8010405@redhat.com> X-ASG-Orig-Subj: Re: [PATCH 2/2] block: fix accounting bug on cross partition merges In-Reply-To: <4D2342E1.8010405@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Barracuda-Connect: mail1.int.fusionio.com[10.101.1.21] X-Barracuda-Start-Time: 1294236042 X-Barracuda-URL: http://10.101.1.181:8000/cgi-mod/mark.cgi X-Barracuda-Spam-Score: 0.41 X-Barracuda-Spam-Status: No, SCORE=0.41 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=9.0 tests=SUBJECT_FUZZY_TION X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.2.51500 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- 0.41 SUBJECT_FUZZY_TION Attempt to obfuscate words in Subject: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011-01-04 16:55, Jerome Marchand wrote: > + } else { > + part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq)); > + if (!kref_test_and_get(&part->ref)) { > + /* > + * The partition is already being removed, > + * the request will be accounted on the disk only > + * > + * We take a reference on disk->part0 although that > + * partition will never be deleted, so we can treat > + * it as any other partition. > + */ > + part = &rq->rq_disk->part0; > + kref_get(&part->ref); > + } This still doesn't work. So you are inside the if {} block, you know what someone has dropped the last reference and the call_rcu() is being scheduled. Adding a reference now will not prevent 'part' from going away as soon as you do part_stat_unlock(). As per my last email, you need a check in the rcu callback to ensure that the ref is 0. -- Jens Axboe