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From: Kent Overstreet To: Linus Torvalds Cc: Matthew Wilcox , Luis Chamberlain , lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm , Daniel Gomez , Pankaj Raghav , Jens Axboe , Dave Chinner , Christoph Hellwig , Chris Mason , Johannes Weiner , Suren Baghdasaryan Subject: Re: [LSF/MM/BPF TOPIC] Measuring limits and enhancing buffered IO Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: E80D2C0002 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: utw5yie3w1dbwxcsxhgbrqg6guwazu7o X-HE-Tag: 1708913223-656901 X-HE-Meta: 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 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 Sun, Feb 25, 2024 at 08:58:28PM -0500, Kent Overstreet wrote: > I think everything works; we need the end result to be consistent with > some total ordering of all the writes, IOW, thread B's write (if fully > within thread A's write) should be fully overwritten or not at all, and > that clearly is the case. But there may be situations involving more > than two threads where things get weirder. Not sure if there's anything interesting or deep here, but this situations where sometimes we've got a global lock and sometimes we've got little locks do seem to come up - it reminded me of Suren's work on the mmap sem recently, and I think I've seen it in other places. Feels like it should at least have a name...