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[49.186.86.168]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7240799bab1sm12188540b3a.107.2024.11.12.16.14.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Nov 2024 16:14:26 -0800 (PST) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1tB11b-00Dr68-38; Wed, 13 Nov 2024 11:14:23 +1100 Date: Wed, 13 Nov 2024 11:14:23 +1100 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, cem@kernel.org Subject: Re: [PATCH 2/3] xfs: delalloc and quota softlimit timers are incoherent Message-ID: References: <20241112221920.1105007-1-david@fromorbit.com> <20241112221920.1105007-3-david@fromorbit.com> <20241112234835.GH9438@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241112234835.GH9438@frogsfrogsfrogs> On Tue, Nov 12, 2024 at 03:48:35PM -0800, Darrick J. Wong wrote: > On Wed, Nov 13, 2024 at 09:05:15AM +1100, Dave Chinner wrote: > > From: Supriya Wickrematillake > > Wow, there are still people working at SGI?? huh, that's a git-send-email screwup. It must have pulled that from the quote of the initial quota commit: > > This debug was introduced in: > > > > commit 0d5ad8383061fbc0a9804fbb98218750000fe032 > > Author: Supriya Wickrematillake > > Date: Wed May 15 22:44:44 1996 +0000 > > > > initial checkin > > quotactl syscall functions. Here, and decided to ignore the actual "From: dchinner@redhat" tag in the local commit message. Great work, git! > > The very first quota support commit back in 1996. This is zero-day > > debug for Irix and, as it turns out, a zero-day bug in the debug > > code because the delalloc code on Irix didn't update the softlimit > > timers, either. > > > > IOWs, this issue has been in the code for 28 years. > > > > We obviously don't care if soft limit timers are a bit rubbery when > > we have delalloc reservations in memory. Production systems running > > quota reports have been exposed to this situation for 28 years and > > nobody has noticed it, so the debug code is essentially worthless at > > this point in time. > > > > We also have the on-disk dquot verifiers checking that the soft > > limit timer is running whenever the dquot is over the soft limit > > before we write it to disk and after we read it from disk. These > > aren't firing, so it is clear the issue is purely a temporary > > in-memory incoherency that I never would have noticed had the test > > not silently failed to unmount the filesystem. > > > > Hence I'm simply going to trash this runtime debug because it isn't > > useful in the slightest for catching quota bugs. > > > > Signed-off-by: Dave Chinner > > Agreed! I've hit this once in a blue moon and didn't think it was > especially useful either. > > Reviewed-by: Darrick J. Wong Thanks! -Dave. -- Dave Chinner david@fromorbit.com