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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tH3T7-00000004LuH-0Jgq; Fri, 29 Nov 2024 16:03:45 +0000 Date: Fri, 29 Nov 2024 16:03:44 +0000 From: Matthew Wilcox To: Lorenzo Stoakes Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand Subject: Re: [PATCH v2] perf: map pages in advance Message-ID: References: <20241129153134.82755-1-lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241129153134.82755-1-lorenzo.stoakes@oracle.com> X-Rspamd-Queue-Id: A7FE31C0003 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 6w91qw3d3qkxb95mat9j1zwaqjm8jpc5 X-HE-Tag: 1732896233-334483 X-HE-Meta: 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 ti+4aS63 +YcUACq28g6yVgeIF15f9XLvP8w1Xw1mhgsTnd6KelrMzcaKyagy0imxM6Tu9fJ4qEdZ5jW+cS47BurNS85LmjGhNfZuZtM0btRgY3QA7Zdb6fSlBJQrGQvBnfZdfe58waCnkYZ6u21cxNcQkXeCUQff0n8TQCcktX8cQ/QLV3RggkAi3bRnCFNDKbpIhm6Jr9YJls5r0One+aGP2bPxW+oGitpz6xF38QkM/GN+oPLWaQG8= 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 Fri, Nov 29, 2024 at 03:31:34PM +0000, Lorenzo Stoakes wrote: > While it is not ideal to use a VM_PFNMAP here, doing anything else will > result in the page_mkwrite() hook need to be provided, which requires the > same page->mapping hack this patch seeks to undo. Or we could map the first page read-write to begin with ... ? Or we could implement a page_mkwrite handler, but do the permissions change in the driver and return VM_FAULT_NOPAGE. I don't think we should do the second option in this driver, but mentioning it because we're going to need to have A Talk about fb_defio.