From patchwork Fri Oct 10 14:23:32 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 5065871 Return-Path: X-Original-To: patchwork-ocfs2-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 81366C11AD for ; Fri, 10 Oct 2014 14:26:00 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 031FF2024F for ; Fri, 10 Oct 2014 14:25:59 +0000 (UTC) Received: from aserp1040.oracle.com (aserp1040.oracle.com [141.146.126.69]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 333EB20222 for ; Fri, 10 Oct 2014 14:25:57 +0000 (UTC) Received: from acsinet22.oracle.com (acsinet22.oracle.com [141.146.126.238]) by aserp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id s9AEPXFM014880 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 10 Oct 2014 14:25:34 GMT Received: from oss.oracle.com (oss-external.oracle.com [137.254.96.51]) by acsinet22.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s9AEPWgL028247 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 10 Oct 2014 14:25:33 GMT Received: from localhost ([127.0.0.1] helo=oss.oracle.com) by oss.oracle.com with esmtp (Exim 4.63) (envelope-from ) id 1Xcb8O-0001Fd-L5; Fri, 10 Oct 2014 07:25:32 -0700 Received: from ucsinet22.oracle.com ([156.151.31.94]) by oss.oracle.com with esmtp (Exim 4.63) (envelope-from ) id 1Xcb75-00013J-Eo for ocfs2-devel@oss.oracle.com; Fri, 10 Oct 2014 07:24:11 -0700 Received: from aserp1030.oracle.com (aserp1030.oracle.com [141.146.126.68]) by ucsinet22.oracle.com (8.14.5+Sun/8.14.5) with ESMTP id s9AEOAVZ008367 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL) for ; Fri, 10 Oct 2014 14:24:11 GMT Received: from aserp2040.oracle.com (aserp2040.oracle.com [141.146.126.75]) by aserp1030.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id s9AEOAIq023725 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 10 Oct 2014 14:24:10 GMT Received: from pps.filterd (aserp2040.oracle.com [127.0.0.1]) by aserp2040.oracle.com (8.14.7/8.14.7) with SMTP id s9AEO9m5044540 for ; Fri, 10 Oct 2014 14:24:10 GMT Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by aserp2040.oracle.com with ESMTP id 1pxec2ajm3-1 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NOT) for ; Fri, 10 Oct 2014 14:24:09 +0000 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id D02FAADE6; Fri, 10 Oct 2014 14:24:03 +0000 (UTC) Received: by quack.suse.cz (Postfix, from userid 1000) id CFE768201E; Fri, 10 Oct 2014 16:24:01 +0200 (CEST) From: Jan Kara To: linux-fsdevel@vger.kernel.org Date: Fri, 10 Oct 2014 16:23:32 +0200 Message-Id: <1412951028-4085-28-git-send-email-jack@suse.cz> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1412951028-4085-1-git-send-email-jack@suse.cz> References: <1412951028-4085-1-git-send-email-jack@suse.cz> X-ServerName: cantor2.suse.de X-Proofpoint-Virus-Version: vendor=nai engine=5600 definitions=7586 signatures=670543 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=1 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1402240000 definitions=main-1410100121 Cc: Dave Kleikamp , jfs-discussion@lists.sourceforge.net, tytso@mit.edu, Jeff Mahoney , Mark Fasheh , Dave Chinner , reiserfs-devel@vger.kernel.org, xfs@oss.sgi.com, cluster-devel@redhat.com, Jan Kara , linux-ext4@vger.kernel.org, Steven Whitehouse , ocfs2-devel@oss.oracle.com, viro@zeniv.linux.org.uk Subject: [Ocfs2-devel] [PATCH] quota: Fix race between dqput() and dquot_scan_active() X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com X-Source-IP: acsinet22.oracle.com [141.146.126.238] X-Spam-Status: No, score=-5.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Currently last dqput() can race with dquot_scan_active() causing it to call callback for an already deactivated dquot. The race is as follows: CPU1 CPU2 dqput() spin_lock(&dq_list_lock); if (atomic_read(&dquot->dq_count) > 1) { - not taken if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) { spin_unlock(&dq_list_lock); ->release_dquot(dquot); if (atomic_read(&dquot->dq_count) > 1) - not taken dquot_scan_active() spin_lock(&dq_list_lock); if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) - not taken atomic_inc(&dquot->dq_count); spin_unlock(&dq_list_lock); - proceeds to release dquot ret = fn(dquot, priv); - called for inactive dquot Fix the problem by making sure possible ->release_dquot() is finished by the time we call the callback and new calls to it will notice reference dquot_scan_active() has taken and bail out. Signed-off-by: Jan Kara --- fs/quota/dquot.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) This is the last patch needed to make ocfs2 quotas rock solid in my testing. I will carry it in my tree and push it to Linus soon. diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c index 831d49a4111f..cfc8dcc16043 100644 --- a/fs/quota/dquot.c +++ b/fs/quota/dquot.c @@ -581,9 +581,17 @@ int dquot_scan_active(struct super_block *sb, dqstats_inc(DQST_LOOKUPS); dqput(old_dquot); old_dquot = dquot; - ret = fn(dquot, priv); - if (ret < 0) - goto out; + /* + * ->release_dquot() can be racing with us. Our reference + * protects us from new calls to it so just wait for any + * outstanding call and recheck the DQ_ACTIVE_B after that. + */ + wait_on_dquot(dquot); + if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) { + ret = fn(dquot, priv); + if (ret < 0) + goto out; + } spin_lock(&dq_list_lock); /* We are safe to continue now because our dquot could not * be moved out of the inuse list while we hold the reference */