From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug() Date: Fri, 11 Sep 2015 12:49:18 -0600 Message-ID: <20150911184918.GA19259@kernel.dk> References: <20150909152323.GB3784@ret.masoncoding.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: , Josef Bacik , Dave Chinner To: Chris Mason Return-path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:37388 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751532AbbIKStW (ORCPT ); Fri, 11 Sep 2015 14:49:22 -0400 Content-Disposition: inline In-Reply-To: <20150909152323.GB3784@ret.masoncoding.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Sep 09 2015, Chris Mason wrote: > Commit d353d7587 added a plug/finish_plug pair to writeback_sb_inodes, > but writeback_sb_inodes has a horrible secret...it's called with the > wb->list_lock held. > > Btrfs raid5/6 and MD raid10 have horrible secrets of their own...they > both do allocations in their unplug callbacks. > > None of the options to fix it are very pretty. We don't want to kick > off workers for all of these unplugs, and the lock doesn't look hot > enough to justify bigger restructuring. > > [ 2854.025042] BUG: sleeping function called from invalid context at mm/page_alloc.c:3189 > [ 2854.041366] in_atomic(): 1, irqs_disabled(): 0, pid: 145562, name: kworker/u66:15 > [ 2854.056813] INFO: lockdep is turned off. > [ 2854.064870] CPU: 13 PID: 145562 Comm: kworker/u66:15 Not tainted 4.2.0-mason+ #1 > [ 2854.080082] Hardware name: ZTSYSTEMS Echo Ridge T4 /A9DRPF-10D, BIOS 1.07 05/10/2012 > [ 2854.096211] Workqueue: writeback wb_workfn (flush-btrfs-244) > [ 2854.107821] ffffffff81a2bbee ffff880ee09a7598 ffffffff813307bb ffff880ee09a7598 > [ 2854.123162] ffff881010d1ca00 ffff880ee09a75c8 ffffffff81086615 0000000000000000 > [ 2854.138556] 0000000000000000 0000000000000c75 ffffffff81a2bbee ffff880ee09a75f8 > [ 2854.153936] Call Trace: > [ 2854.181101] [] __might_sleep+0x52/0x90 > [ 2854.192136] [] __alloc_pages_nodemask+0x344/0xbe0 > [ 2854.229682] [] alloc_pages_current+0x10a/0x1e0 > [ 2854.255508] [] full_stripe_write+0x59/0xc0 [btrfs] > [ 2854.268600] [] __raid56_parity_write+0x39/0x60 [btrfs] > [ 2854.282385] [] run_plug+0x11b/0x140 [btrfs] > [ 2854.294259] [] btrfs_raid_unplug+0x23/0x70 [btrfs] > [ 2854.307334] [] blk_flush_plug_list+0x82/0x1f0 > [ 2854.319542] [] blk_finish_plug+0x34/0x50 > [ 2854.330878] [] writeback_sb_inodes+0x122/0x580 > [ 2854.343256] [] wb_writeback+0x136/0x4e0 > > Signed-off-by: Chris Mason Reviewed-by: Jens Axboe -- Jens Axboe