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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 A50A0C433DF for ; Tue, 11 Aug 2020 13:48:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 72D092076B for ; Tue, 11 Aug 2020 13:48:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597153694; bh=5yMEp9SyDxPuo/xXOdliP4xpnslVqaycciG2uRFajHk=; h=Date:From:To:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=fGrnBRN19YB1zJUhczdk0P8kCo45BPt3FFeoaJk71s7JW49JbN4zYOqZFlZqgM8L8 kd8tfIh4i/HlG5cbUy+SGn/eZayD+Tnxf325mGTphkZMcaXU1pw3Uc8n7W3hrnkJWL /3fifOIaU8KgZ1qo4vqomBcxWt4F4Nf1neoIXhnA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728684AbgHKNr4 (ORCPT ); Tue, 11 Aug 2020 09:47:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:37572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728532AbgHKNrr (ORCPT ); Tue, 11 Aug 2020 09:47:47 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5B3462076B; Tue, 11 Aug 2020 13:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597153666; bh=5yMEp9SyDxPuo/xXOdliP4xpnslVqaycciG2uRFajHk=; h=Date:From:To:Subject:Reply-To:References:In-Reply-To:From; b=wtdh1lcpu2MOuXVkpZaTW+KsbfecM8PsgIi8ucIUwmgrSVpyJ0qQ/hHCVK6hApvLK ONu2szekPDI4KmUgBtuvKcjhuSfczaU0kttSOsEJlJCmNwRxsB0w3uVCCeFBXw6PMd e+d6+mU2CB1qjb0mSvl3OwsEYJ4FUiBqYNm8z+yI= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 26D473522FF7; Tue, 11 Aug 2020 06:47:46 -0700 (PDT) Date: Tue, 11 Aug 2020 06:47:46 -0700 From: "Paul E. McKenney" To: dsterba@suse.cz, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Sasha Levin , linux-btrfs@vger.kernel.org Subject: Re: [PATCH AUTOSEL 4.4 03/16] fs/btrfs: Add cond_resched() for try_release_extent_mapping() stalls Message-ID: <20200811134746.GV4295@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200810191443.3795581-1-sashal@kernel.org> <20200810191443.3795581-3-sashal@kernel.org> <20200811075720.GL2026@twin.jikos.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200811075720.GL2026@twin.jikos.cz> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Tue, Aug 11, 2020 at 09:57:20AM +0200, David Sterba wrote: > On Mon, Aug 10, 2020 at 03:14:30PM -0400, Sasha Levin wrote: > > From: "Paul E. McKenney" > > > > [ Upstream commit 9f47eb5461aaeb6cb8696f9d11503ae90e4d5cb0 ] > > > > Very large I/Os can cause the following RCU CPU stall warning: > > > > RIP: 0010:rb_prev+0x8/0x50 > > Code: 49 89 c0 49 89 d1 48 89 c2 48 89 f8 e9 e5 fd ff ff 4c 89 48 10 c3 4c = > > 89 06 c3 4c 89 40 10 c3 0f 1f 00 48 8b 0f 48 39 cf 74 38 <48> 8b 47 10 48 85 c0 74 22 48 8b 50 08 48 85 d2 74 0c 48 89 d0 48 > > RSP: 0018:ffffc9002212bab0 EFLAGS: 00000287 ORIG_RAX: ffffffffffffff13 > > RAX: ffff888821f93630 RBX: ffff888821f93630 RCX: ffff888821f937e0 > > RDX: 0000000000000000 RSI: 0000000000102000 RDI: ffff888821f93630 > > RBP: 0000000000103000 R08: 000000000006c000 R09: 0000000000000238 > > R10: 0000000000102fff R11: ffffc9002212bac8 R12: 0000000000000001 > > R13: ffffffffffffffff R14: 0000000000102000 R15: ffff888821f937e0 > > __lookup_extent_mapping+0xa0/0x110 > > try_release_extent_mapping+0xdc/0x220 > > btrfs_releasepage+0x45/0x70 > > shrink_page_list+0xa39/0xb30 > > shrink_inactive_list+0x18f/0x3b0 > > shrink_lruvec+0x38e/0x6b0 > > shrink_node+0x14d/0x690 > > do_try_to_free_pages+0xc6/0x3e0 > > try_to_free_mem_cgroup_pages+0xe6/0x1e0 > > reclaim_high.constprop.73+0x87/0xc0 > > mem_cgroup_handle_over_high+0x66/0x150 > > exit_to_usermode_loop+0x82/0xd0 > > do_syscall_64+0xd4/0x100 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > On a PREEMPT=n kernel, the try_release_extent_mapping() function's > > "while" loop might run for a very long time on a large I/O. This commit > > therefore adds a cond_resched() to this loop, providing RCU any needed > > quiescent states. > > > > Signed-off-by: Paul E. McKenney > > Paul, > > this patch was well hidden in some huge RCU pile > (https://lore.kernel.org/lkml/20200623002147.25750-11-paulmck@kernel.org/) > > I wonder why you haven't CCed linux-btrfs, I spotted the patch queued > for stable by incidentally. The timestamp is from June, that's quite > some time ago. We can deal with one more patch and I tend to reply with > acks quickly for easy patches like this to not block other peoples work > but I'm a bit disappointed by sidestepping maintained subsystems. It's > not just this patch, it happens from time time only to increase the > disapointement. My bad, and please accept my apologies. I clearly left out the step of adding proper Cc: lines. :-/ Thanx, Paul