From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 802DFC433E0 for ; Fri, 5 Feb 2021 03:53:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 340C964E24 for ; Fri, 5 Feb 2021 03:53:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231148AbhBEDxk (ORCPT ); Thu, 4 Feb 2021 22:53:40 -0500 Received: from mga04.intel.com ([192.55.52.120]:34512 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230184AbhBEDxi (ORCPT ); Thu, 4 Feb 2021 22:53:38 -0500 IronPort-SDR: JFZrqZ04xrDGVnp+AHYSzyfj8S9cIceHbj9MhSj/eiEFi+PVKFv5hU1f5czDOP4Oeya7++hlc+ 2lrdKV9Eu0ew== X-IronPort-AV: E=McAfee;i="6000,8403,9885"; a="178812605" X-IronPort-AV: E=Sophos;i="5.81,154,1610438400"; d="scan'208";a="178812605" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Feb 2021 19:52:38 -0800 IronPort-SDR: ZtkMwGgKqJszXgT2iemnsvXjrWTCfy7JMDYSFhclK6GT7AqatAZDl6OxFwe30M3WXDZfaXgvBl US14tnKSnCGQ== X-IronPort-AV: E=Sophos;i="5.81,154,1610438400"; d="scan'208";a="393673586" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.147]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Feb 2021 19:52:37 -0800 Date: Thu, 4 Feb 2021 19:52:36 -0800 From: Ira Weiny To: dsterba@suse.cz, clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, Miao Xie , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] fs/btrfs: Fix raid6 qstripe kmap'ing Message-ID: <20210205035236.GB5033@iweiny-DESK2.sc.intel.com> References: <20210128061503.1496847-1-ira.weiny@intel.com> <20210203155648.GE1993@suse.cz> <20210204152608.GF1993@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210204152608.GF1993@suse.cz> User-Agent: Mutt/1.11.1 (2018-12-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 04, 2021 at 04:26:08PM +0100, David Sterba wrote: > On Wed, Feb 03, 2021 at 04:56:48PM +0100, David Sterba wrote: > > On Wed, Jan 27, 2021 at 10:15:03PM -0800, ira.weiny@intel.com wrote: > > > From: Ira Weiny > > > > > > When a qstripe is required an extra page is allocated and mapped. There > > > were 3 problems. > > > > > > 1) There is no reason to map the qstripe page more than 1 time if the > > > number of bits set in rbio->dbitmap is greater than one. > > > 2) There is no reason to map the parity page and unmap it each time > > > through the loop. > > > 3) There is no corresponding call of kunmap() for the qstripe page. > > > > > > The page memory can continue to be reused with a single mapping on each > > > iteration by raid6_call.gen_syndrome() without remapping. So map the > > > page for the duration of the loop. > > > > > > Similarly, improve the algorithm by mapping the parity page just 1 time. > > > > > > Fixes: 5a6ac9eacb49 ("Btrfs, raid56: support parity scrub on raid56") > > > To: Chris Mason > > > To: Josef Bacik > > > To: David Sterba > > > Cc: Miao Xie > > > Signed-off-by: Ira Weiny > > > > > > --- > > > This was found while replacing kmap() with kmap_local_page(). After > > > this patch unwinding all the mappings becomes pretty straight forward. > > > > > > I'm not exactly sure I've worded this commit message intelligently. > > > Please forgive me if there is a better way to word it. > > > > Changelog is good, thanks. I've added stable tags as the missing unmap > > is a potential problem. > > There are lots of tests faling, stack traces like below. I haven't seen > anything obvious in the patch so that needs a closer look and for the > time being I can't add the patch to for-next. :-( I think I may have been off by 1 on the raid6 kmap... Something like this should fix it... diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c index b8a39dad0f00..dbf52f1a379d 100644 --- a/fs/btrfs/raid56.c +++ b/fs/btrfs/raid56.c @@ -2370,7 +2370,7 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio, goto cleanup; } SetPageUptodate(q_page); - pointers[rbio->real_stripes] = kmap(q_page); + pointers[rbio->real_stripes - 1] = kmap(q_page); } atomic_set(&rbio->error, 0); Let me roll a new version. Sorry, Ira > > BUG: kernel NULL pointer dereference, address:0000000000000000 > #PF: supervisor write access in kernel mode > #PF: error_code(0x0002) - not-present page > PGD 0 P4D 0 > Oops: 0002 [#1] PREEMPT SMP > CPU: 2 PID: 17173 Comm: kworker/u8:5 Not tainted5.11.0-rc6-default+ #1422 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014 > Workqueue: btrfs-rmw btrfs_work_helper [btrfs] > RIP: 0010:raid6_avx22_gen_syndrome+0x103/0x140 [raid6_pq] > RSP: 0018:ffffa090042cfcf8 EFLAGS: 00010246 > RAX: ffff9e98e1848e80 RBX: ffff9e98d5849000 RCX:0000000000000020 > RDX: ffff9e98e32be000 RSI: 0000000000000000 RDI:ffff9e98e1848e80 > RBP: 0000000000000000 R08: 0000000000000000 R09:0000000000000001 > R10: ffff9e98e1848e90 R11: ffff9e98e1848e98 R12:0000000000001000 > R13: ffff9e98e1848e88 R14: 0000000000000005 R15:0000000000000002 > FS: 0000000000000000(0000) GS:ffff9e993da00000(0000)knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000000 CR3: 0000000023143003 CR4:0000000000170ea0 > Call Trace: > finish_parity_scrub+0x47b/0x7a0 [btrfs] > raid56_parity_scrub_stripe+0x24e/0x260 [btrfs] > btrfs_work_helper+0xd5/0x1d0 [btrfs] > process_one_work+0x262/0x5f0 > worker_thread+0x4e/0x300 > ? process_one_work+0x5f0/0x5f0 > kthread+0x151/0x170 > ? __kthread_bind_mask+0x60/0x60