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Received: from willy by casper.infradead.org with local (Exim 4.98.1 #2 (Red Hat Linux)) id 1txqOG-0000000DRYG-0hdg; Thu, 27 Mar 2025 16:47:36 +0000 Date: Thu, 27 Mar 2025 16:47:35 +0000 From: Matthew Wilcox To: Alistair Popple Cc: Christoph Hellwig , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 0/6] Allow file-backed or shared device private pages Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Stat-Signature: r7te7x8iof7tsef9pawqj798i7bf454r X-Rspam-User: X-Rspamd-Queue-Id: 594E980006 X-HE-Tag: 1743094058-597187 X-HE-Meta: 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 aGVTNm6n petF12FU8B0CRvjsQuSA0baFJylbyX6VqynI3ZYLetLW/8y8QMihohPbZ8w99sugDDmVVDQU3aufjRqVgl9PhRDqiPUjJ/3WY4F5lmTi3lIlrg95fopTd8eRlA2gNDzZKJryLcShFAhcp8p8+PkDGIYWLwcYjFOTGb3oy3WX8ZF7DUCYzNDp01t1Ymkkzas/bFrH6KW/1/bxYO4gQWFH0yuGfZ04TBJeNRMey 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, Mar 27, 2025 at 07:49:47AM -0700, Alistair Popple wrote: > On Wed, Mar 26, 2025 at 02:14:59AM +0000, Matthew Wilcox wrote: > > So, there's no need to put DEVICE_PRIVATE pages in the page cache. > > Instead the GPU will take a copy of the page(s). We agreed that there > > will have to be some indication (probably a folio flag?) that the GPU has > > or may have a copy of (some of) the folio so that it can be invalidated > > if the page is removed due to truncation / eviction. > > > > Alistair, let me know if that's not what you think we agreed to ;-) > > That all looks about right. I think the flag/indication is a good idea and is > probably the best solution, but I will need to write the code to truely convince > myself of that :-) It might end up making more sense to make it a per-VMA flag or a per-inode flag, but that's probably something you're in a better position to determine than I am.