From patchwork Thu Feb 19 03:02:23 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kiyoshi Ueda X-Patchwork-Id: 7907 X-Patchwork-Delegate: agk@redhat.com Received: from hormel.redhat.com (hormel1.redhat.com [209.132.177.33]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n1J32wtU022177 for ; Thu, 19 Feb 2009 03:02:58 GMT Received: from listman.util.phx.redhat.com (listman.util.phx.redhat.com [10.8.4.110]) by hormel.redhat.com (Postfix) with ESMTP id 179B161B971; Wed, 18 Feb 2009 22:02:57 -0500 (EST) Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by listman.util.phx.redhat.com (8.13.1/8.13.1) with ESMTP id n1J32te0005862 for ; Wed, 18 Feb 2009 22:02:56 -0500 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n1J32q2k001613 for ; Wed, 18 Feb 2009 22:02:52 -0500 Received: from tyo202.gate.nec.co.jp (TYO202.gate.nec.co.jp [202.32.8.206]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n1J32bL2009850 for ; Wed, 18 Feb 2009 22:02:38 -0500 Received: from mailgate3.nec.co.jp ([10.7.69.160]) by tyo202.gate.nec.co.jp (8.13.8/8.13.4) with ESMTP id n1J32N2s025791; Thu, 19 Feb 2009 12:02:23 +0900 (JST) Received: (from root@localhost) by mailgate3.nec.co.jp (8.11.7/3.7W-MAILGATE-NEC) id n1J32Nq25012; Thu, 19 Feb 2009 12:02:23 +0900 (JST) Received: from mailsv.linux.bs1.fc.nec.co.jp (mailsv.linux.bs1.fc.nec.co.jp [10.34.125.2]) by mailsv3.nec.co.jp (8.13.8/8.13.4) with ESMTP id n1J32NRh001535; Thu, 19 Feb 2009 12:02:23 +0900 (JST) Received: from elcondor.linux.bs1.fc.nec.co.jp (elcondor.linux.bs1.fc.nec.co.jp [10.34.125.195]) by mailsv.linux.bs1.fc.nec.co.jp (Postfix) with ESMTP id 238A1E482C3; Thu, 19 Feb 2009 12:02:23 +0900 (JST) Message-ID: <499CCBBF.4090602@ct.jp.nec.com> Date: Thu, 19 Feb 2009 12:02:23 +0900 From: Kiyoshi Ueda User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Christof Schmitt Subject: Re: [dm-devel] [PATCH] dm: Fix lock dependency warning for request based dm References: <20090218142154.GA1782@schmichrtp.de.ibm.com> In-Reply-To: <20090218142154.GA1782@schmichrtp.de.ibm.com> X-RedHat-Spam-Score: -0.4 X-Scanned-By: MIMEDefang 2.58 on 172.16.52.254 X-Scanned-By: MIMEDefang 2.63 on 172.16.48.31 X-loop: dm-devel@redhat.com Cc: device-mapper development X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.5 Precedence: junk Reply-To: device-mapper development List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com Hi Christof, On 2009/02/18 23:21 +0900, Christof Schmitt wrote: > > From: Christof Schmitt > > > > Testing with request based dm multipathing and lock dependency checking > > revealed this problem. Fix this by disabling interrupts when acquiring the > > map_lock from the ioctl call in __bind and __unbind. > > > > It seems that the problem has been introduced with this patch: > > http://lkml.indiana.edu/hypermail/linux/kernel/0810.0/1067.html Thank you for your testing request-based dm-multipath and the patch. Attached is a patch to fix it. Since request-based dm gets map_lock after taking queue_lock with interrupt disabled, we have to use save/restore variant. (By the way, although lockdep warns the deadlock possibility, currently there should be no such code path in request-based dm where request_fn is called from the interrupt context.) I have done simple build and boot testings, but haven't done other testings (e.g. stress testing) yet. I will include this patch to the next update after such testings. Thanks, Kiyoshi Ueda --- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel Index: linux-2.6.29-rc2/drivers/md/dm.c =================================================================== --- linux-2.6.29-rc2.orig/drivers/md/dm.c +++ linux-2.6.29-rc2/drivers/md/dm.c @@ -504,12 +504,13 @@ static int queue_io(struct mapped_device struct dm_table *dm_get_table(struct mapped_device *md) { struct dm_table *t; + unsigned long flags; - read_lock(&md->map_lock); + read_lock_irqsave(&md->map_lock, flags); t = md->map; if (t) dm_table_get(t); - read_unlock(&md->map_lock); + read_unlock_irqrestore(&md->map_lock, flags); return t; } @@ -1892,6 +1893,7 @@ static int __bind(struct mapped_device * { struct request_queue *q = md->queue; sector_t size; + unsigned long flags; size = dm_table_get_size(t); @@ -1921,10 +1923,10 @@ static int __bind(struct mapped_device * if (dm_table_request_based(t) && !blk_queue_stopped(q)) stop_queue(q); - write_lock(&md->map_lock); + write_lock_irqsave(&md->map_lock, flags); md->map = t; dm_table_set_restrictions(t, q); - write_unlock(&md->map_lock); + write_unlock_irqrestore(&md->map_lock, flags); return 0; } @@ -1932,14 +1934,15 @@ static int __bind(struct mapped_device * static void __unbind(struct mapped_device *md) { struct dm_table *map = md->map; + unsigned long flags; if (!map) return; dm_table_event_callback(map, NULL, NULL); - write_lock(&md->map_lock); + write_lock_irqsave(&md->map_lock, flags); md->map = NULL; - write_unlock(&md->map_lock); + write_unlock_irqrestore(&md->map_lock, flags); dm_table_destroy(map); }