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Received: from [127.0.0.2] (localhost [127.0.0.1]) by hr2.samba.org with esmtpsa (TLS1.3:ECDHE_SECP256R1__ECDSA_SECP256R1_SHA256__CHACHA20_POLY1305:256) (Exim) id 1tATxD-00A3CN-1S; Mon, 11 Nov 2024 12:55:39 +0000 Message-ID: <63af3bba-c824-4b2c-a670-6329eeb232aa@samba.org> Date: Mon, 11 Nov 2024 13:55:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHSET v4] Uncached buffered IO To: Jens Axboe , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Cc: hannes@cmpxchg.org, clm@meta.com, linux-kernel@vger.kernel.org References: <20241108174505.1214230-1-axboe@kernel.dk> Content-Language: en-US, de-DE From: Stefan Metzmacher In-Reply-To: <20241108174505.1214230-1-axboe@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A5382140025 X-Stat-Signature: yide71p986e6ki43sf7myea8qjdt6jax X-Rspam-User: X-HE-Tag: 1731329716-587434 X-HE-Meta: U2FsdGVkX18uD4RCBAVmUdOIak5GtRJYn8h+A1OZSuGspIBnlSTpm8S8m0MP/P2H5rbALuHt2EE+H0LTW2wSEylN/qSIVsYUn7KKYFi4aQnhZj9iJCtWvRqqs6S5yqt3qsSCEakMvc7i2coWxpg3IWuyInPh0yyVHdID409bxfRE5tO/49LNZSEGP/fPV5UAf8bFeD9JfTufwz5McDJDi/oJkxYydsf2jVHgxp0U34tbY+Qqfx14L705kp7OL+In7qxvxQcIrFQthUn+pMtlSywKfgVHdWSMHwij+CjPtoi2ago+pABtsQEwoJpc3wSfYP4bULIHcJxGgFnkxsDXXhv9wR87NpoObcDmWvlNL3IyPBfayYxpEcW9W/t6xFcGkxgwSUSxKfAFxpK0WAc6dnACh9Wtm25Ny9cGUFyi0EIyew2Z6exceP51uxZMx6QeirSkp5exKeMbX1QN636V+4MncLqv69uL0R38B9NF9tRisN9Nd4F+GbfOgR3zyjKZrghC6VycA/pYP2raMJVjkV1mbLxCJkNbm4VfvRVScQVzkkbSPHqUn1Ax+ShUZD2mhkprwXl6F11e4nHvkJgBCY/5NP4e/mSiGMGoskFOvUb9EseiJMuMC+66dEA/d/R+wrE2EePdDf0VCX4/9T1cO9/K5094yThRNbVCzNgwOejd84w3PsxSY5KyaES8BbjS6UOWMeczTbBbHWnZxWHcfe0F8H4i6k8+kAYx6Hxq78g76R5HdPTMB0AUQ1YALUQhCcT3vSIUwT10MF7G2Iu52oQ4K05Ccby1KXiVvnmnRIzYSEQFvTffSXrR12Ao3Eavx8xIoQxvin5lgpp8wBNiK8oISenaZaiZ2jT96mwqlSaywxQuLclCfoz7vOlwCZYdltxC9PLYDx0sZkQqxjFh68l9VRlxMkjbI1TsUCxvW9mohIDuWBnqXbMkA+Bl6SyPVCfIYTx/piYOeI/yu2M b+pk1Puo r2Plf9M16rfUScPaID1+JSKl2vgGPEMpunhEEwbrKrBRJIdnemzxiXpmK3sTfvPS9zWCTgTbSM9ln9AWAI4MvTVSughU+Qld6yWNdofR6PzMwvjJigpRdjPXNH782Cwnh50SDgFUpIGgzp5FUdVFd2W4sZSnfpLeRDiGkbY0wNtmWKjEofjyOa7yQ4yBfT9Ka5k46k4CBlWFem5z8dfcllZ1G+YR8Z9EvNDUwk4wP1IiAw6Hr5blU+rh3aCsO6eYv+u81hK8/moQFRkXF/tBX6MAo7Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000009, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Jens, I'm wondering about the impact on memory mapped files. Let's say one (or more) process(es) called mmap on a file in order to use the content of the file as persistent shared memory. As far as I understand pages from the page cache are used for this. Now another process uses RWF_UNCACHED for a read of the same file. What happens if the pages are removed from the page cache? Or is the removal deferred based on some refcount? Thanks! metze