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Wysocki" , Andrew Morton , Mike Marciniszyn , Michael Guralnik , Dan Williams , Ard Biesheuvel , Valentine Sinitsyn , Lukas Wunner Subject: Re: [PATCH 1/6] kernfs: create vm_operations_struct without page_mkwrite() Message-ID: References: <20240605192934.742369-1-martin.oliveira@eideticom.com> <20240605192934.742369-2-martin.oliveira@eideticom.com> <2024060658-ember-unblessed-4c74@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2024060658-ember-unblessed-4c74@gregkh> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Stat-Signature: ibnugxbck7q79w34fwfu9fs7zmjk3z9u X-Rspamd-Queue-Id: 3256D14000D X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1717736617-340343 X-HE-Meta: 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 IvktL1JI kryB03jZLZPuFTYxGQ5VA/HGSLy64Q3jiX/GLa/EBcn3ciJTQBoD7ZSZbDQUknZsi+UdO/BW5PJPPlR3qJkZsU4ZwFRWycmylIu9Qt0tvCYhuswyDOQ+U4vVvtWAGhZzmNy/d/8HEo67/ryvYbpOc4Z25a2cGi8zTfhCYQnv4o8+wLuLDvjLKsusg6QFdtvKDXwnW95Pi8wlnCUDJyGA1AKzu0LEKPNujHw3fkcIBRkqKhPKzVrTS2BodSyAk7GbQ24nrR9j+EgZR3gk0fPEStumsB9CFdRspjFZQHjFJqZCNt2d3svqtYQQEeHNwEgPDlrxqwVodl6g/qXu84cNbwRQEvDxyVT7LfLhRwzHEQrCcMrF06lYBC8yHsZH6VHDLbff+1irNeFo/vNSFwCTHtrMy76ADWt2UICtTF7MuitipBtYdQ1UO2Quk7A== 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 Thu, Jun 06, 2024 at 10:54:06PM +0200, Greg Kroah-Hartman wrote: > On Wed, Jun 05, 2024 at 01:29:29PM -0600, Martin Oliveira wrote: > > The standard kernfs vm_ops installs a page_mkwrite() operator which > > modifies the file update time on write. > > > > This not always required (or makes sense), such as in the P2PDMA, which > > uses the sysfs file as an allocator from userspace. > > That's not a good idea, please don't do that. sysfs binary files are > "pass through", why would you want to use this as an allocator? I think the real question is why sysfs binary files implement page_mkwrite by default. page_mkwrite is needed for file systems that need to allocate space from a free space pool, which seems odd for sysfs.