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Wong" , Theodore Ts'o , Andreas Dilger , Chris Mason , Josef Bacik , David Sterba , Hugh Dickins , Andrew Morton , Chuck Lever , Vadim Fedorenko Cc: Randy Dunlap , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v8 01/11] timekeeping: move multigrain timestamp floor handling into timekeeper In-Reply-To: <753938ef8e46e9f3d9ea7d977537cd8f5a6533b2.camel@kernel.org> References: <20240914-mgtime-v8-0-5bd872330bed@kernel.org> <20240914-mgtime-v8-1-5bd872330bed@kernel.org> <87bk050xb9.ffs@tglx> <753938ef8e46e9f3d9ea7d977537cd8f5a6533b2.camel@kernel.org> Date: Mon, 30 Sep 2024 22:15:39 +0200 Message-ID: <871q102904.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Stat-Signature: eo7rh7krwjjb3ejtj75bsp9bgqcacbip X-Rspamd-Queue-Id: 42B56C0010 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1727727343-644133 X-HE-Meta: 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 6NrF/baC wr0os5Whn7zXhMw/Cb/xXCBGcWM26qA5KhVijd791XaT+2m/hfNjsQCPhFF3l/pnc+ur9yr1bZxhWwYfCwdSBEZp3dIjP5+g2IoQZtO6dSudhWNydY05cJ2AaxbUS6x39yXqSLNMWuvaLD0hFnyccLC84bQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 30 2024 at 15:27, Jeff Layton wrote: > On Mon, 2024-09-30 at 21:13 +0200, Thomas Gleixner wrote: >> So if that's the intended behaviour then the changelog is misleading at >> best. > > That is the intended behavior and I'll plan to fix the changelog to > clarify this point: > > If someone jumps the realtime clock backward by a large value, then the > realtime timestamp _can_ appear to go backward. This is a problem today > even without this patchset. Correct. > If two files get stamped and a realtime clock jump backward happens in > between them, all bets are off as to which one will appear to have been > modified first. I don't think that is something we can reasonably > prevent, since we must stamp files according to the realtime clock. True. I just was utterly confused about the changelog. > The main thing I'm trying to prevent is the timestamps being misordered > in the absence of such a clock jump. Without tracking the floor as I am > here, that's a possibility. Correct.