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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: <4aa41dcb6f4be736355506dd500c4d255e008764.camel@kernel.org> References: <20240914-mgtime-v8-0-5bd872330bed@kernel.org> <20240914-mgtime-v8-1-5bd872330bed@kernel.org> <87a5g79aag.ffs@tglx> <874j6f99dg.ffs@tglx> <878qv90x6w.ffs@tglx> <4933075b1023f466edb516e86608e0938de28c1d.camel@kernel.org> <87y138zyfu.ffs@tglx> <79a32ab9308d6e63e066aa17c5c2492b51b55850.camel@kernel.org> <87plokzuy6.ffs@tglx> <4aa41dcb6f4be736355506dd500c4d255e008764.camel@kernel.org> Date: Tue, 01 Oct 2024 14:45:17 +0200 Message-ID: <8734lgyote.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Stat-Signature: 5wsb8kqrwitswtteqomzwkkc5jkjdi5s X-Rspamd-Queue-Id: C1E534000D X-Rspamd-Server: rspam11 X-HE-Tag: 1727786719-903837 X-HE-Meta: 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 fA1zret9 sQUm9KpQBiE5NyvwE2fM3GnqFuTF4qJn9i+j18rMuUG2OgdEGPr6GHGyvWOZZDfrVCQazurzexO4lqXPLASOQiPfoXQAFAeNxh1tQMIs3qjUBS+cuiw6u/EqsqPnAP6mLGXvLzhDFul9Gp7g88gBSax3ZyIjk4d5bCV8W 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 Tue, Oct 01 2024 at 05:45, Jeff Layton wrote: > On Mon, 2024-09-30 at 23:35 +0200, Thomas Gleixner wrote: >> > I certainly wouldn't rule out a workqueue job calling that function, >> > but this is something we do while dirtying an inode, and that's not >> > typically done in interrupt context. >> >> The reason I'm asking is that if it's always syscall context, >> i.e. write() or io_uring()/RPC request etc., then you can avoid the >> whole global floor value dance and make it strictly per thread, which >> simplifies the exercise significantly. >> > > I'm not sure I follow what you're proposing here. > > Consider two threads doing writes serially to different files. IOW, the > second thread enters the write() syscall after the first thread returns > from its write(). In that situation, the second timestamp mustn't > appear to be earlier than the first (assuming no backward clock jump, > of course). > > How would we ensure that with only per-thread structures? Bah. Right. Ignore my sleep deprived rambling.