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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7B2CFC433F5 for ; Sat, 5 Mar 2022 14:16:07 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6D38D10E423; Sat, 5 Mar 2022 14:16:06 +0000 (UTC) Received: from lgeamrelo11.lge.com (lgeamrelo12.lge.com [156.147.23.52]) by gabe.freedesktop.org (Postfix) with ESMTP id 0487810E423 for ; Sat, 5 Mar 2022 14:16:03 +0000 (UTC) Received: from unknown (HELO lgemrelse7q.lge.com) (156.147.1.151) by 156.147.23.52 with ESMTP; 5 Mar 2022 23:16:01 +0900 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: byungchul.park@lge.com Received: from unknown (HELO X58A-UD3R) (10.177.244.38) by 156.147.1.151 with ESMTP; 5 Mar 2022 23:16:01 +0900 X-Original-SENDERIP: 10.177.244.38 X-Original-MAILFROM: byungchul.park@lge.com Date: Sat, 5 Mar 2022 23:15:38 +0900 From: Byungchul Park To: Theodore Ts'o Subject: Re: Report 2 in ext4 and journal based on v5.17-rc1 Message-ID: <20220305141538.GA31268@X58A-UD3R> References: <1646285013-3934-1-git-send-email-byungchul.park@lge.com> <20220304004237.GB6112@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: hamohammed.sa@gmail.com, jack@suse.cz, peterz@infradead.org, daniel.vetter@ffwll.ch, amir73il@gmail.com, david@fromorbit.com, dri-devel@lists.freedesktop.org, chris@chris-wilson.co.uk, bfields@fieldses.org, linux-ide@vger.kernel.org, adilger.kernel@dilger.ca, joel@joelfernandes.org, cl@linux.com, will@kernel.org, duyuyang@gmail.com, sashal@kernel.org, paolo.valente@linaro.org, damien.lemoal@opensource.wdc.com, willy@infradead.org, hch@infradead.org, airlied@linux.ie, mingo@redhat.com, djwong@kernel.org, vdavydov.dev@gmail.com, rientjes@google.com, dennis@kernel.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, ngupta@vflare.org, johannes.berg@intel.com, jack@suse.com, dan.j.williams@intel.com, josef@toxicpanda.com, rostedt@goodmis.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, jglisse@redhat.com, viro@zeniv.linux.org.uk, tglx@linutronix.de, mhocko@kernel.org, vbabka@suse.cz, melissa.srw@gmail.com, sj@kernel.org, rodrigosiqueiramelo@gmail.com, kernel-team@lge.com, gregkh@linuxfoundation.org, jlayton@kernel.org, linux-kernel@vger.kernel.org, penberg@kernel.org, minchan@kernel.org, hannes@cmpxchg.org, tj@kernel.org, akpm@linux-foundation.org, torvalds@linux-foundation.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Fri, Mar 04, 2022 at 10:26:23PM -0500, Theodore Ts'o wrote: > On Fri, Mar 04, 2022 at 09:42:37AM +0900, Byungchul Park wrote: > > > > All contexts waiting for any of the events in the circular dependency > > chain will be definitely stuck if there is a circular dependency as I > > explained. So we need another wakeup source to break the circle. In > > ext4 code, you might have the wakeup source for breaking the circle. > > > > What I agreed with is: > > > > The case that 1) the circular dependency is unevitable 2) there are > > another wakeup source for breadking the circle and 3) the duration > > in sleep is short enough, should be acceptable. > > > > Sounds good? > > These dependencies are part of every single ext4 metadata update, > and if there were any unnecessary sleeps, this would be a major > performance gap, and this is a very well studied part of ext4. > > There are some places where we sleep, sure. In some case > start_this_handle() needs to wait for a commit to complete, and the > commit thread might need to sleep for I/O to complete. But the moment > the thing that we're waiting for is complete, we wake up all of the > processes on the wait queue. But in the case where we wait for I/O > complete, that wakeupis coming from the device driver, when it > receives the the I/O completion interrupt from the hard drive. Is > that considered an "external source"? Maybe DEPT doesn't recognize > that this is certain to happen just as day follows the night? (Well, > maybe the I/O completion interrupt might not happen if the disk drive > bursts into flames --- but then, you've got bigger problems. :-) Almost all you've been blaming at Dept are totally non-sense. Based on what you're saying, I'm conviced that you don't understand how Dept works even 1%. You don't even try to understand it before blame. You don't have to understand and support it. But I can't response to you if you keep saying silly things that way. > In any case, if DEPT is going to report these "circular dependencies > as bugs that MUST be fixed", it's going to be pure noise and I will > ignore all DEPT reports, and will push back on having Lockdep replaced Dept is going to be improved so that what you are concerning about won't be reported. > by DEPT --- because Lockdep give us actionable reports, and if DEPT Right. Dept should give actionable reports, too. > can't tell the difference between a valid programming pattern and a > bug, then it's worse than useless. Needless to say.