From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F1271CF256B for ; Wed, 19 Nov 2025 09:17:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 57DE56B008C; Wed, 19 Nov 2025 04:17:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 52CD86B00A2; Wed, 19 Nov 2025 04:17:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 41C0A6B00A3; Wed, 19 Nov 2025 04:17:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 2DF806B008C for ; Wed, 19 Nov 2025 04:17:28 -0500 (EST) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id CBFE758B58 for ; Wed, 19 Nov 2025 09:17:27 +0000 (UTC) X-FDA: 84126803334.26.329007F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf26.hostedemail.com (Postfix) with ESMTP id 03531140015 for ; Wed, 19 Nov 2025 09:17:25 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=r1eviRHi; spf=pass (imf26.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763543846; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6Y5kJQVbOla5fH5duGClMNZK8b9PMSU4r9dncswVtoc=; b=qjyO75qasjlztEvjptZhDBhXZrXQvbp3tGSklqT1K0vTspOAP0oFEPi24d2wQZ3xoU42s0 TZErjG0eKe34IeHZL/4e+JQORSRmUxlzXkE0MqNeCJFGQx9kpVYbGSVpVnO2HRTQmuYHW1 RPJGZSB7GlDzwJZXlIiNf9OIT0wEV7Y= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=r1eviRHi; spf=pass (imf26.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763543846; a=rsa-sha256; cv=none; b=E8WlwmNo7Cyp8HYPQ0Wb1y3UaY5PDLr3AnFgUTbAJ7z9kgegiQODtxeOuKIMy9bSwIqSrg 9KppN17/hd/durHZzJwdmHFfc8mMS8EtQNzEoqgHDRtZgcxi7q+v2bQ4VLnW2h3xyWQZmk CkUo3eVMpitMck5biyf1sWqSOX3CG9I= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id CF46443B21; Wed, 19 Nov 2025 09:17:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72CC8C113D0; Wed, 19 Nov 2025 09:17:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763543844; bh=+ffPga0iEGIkgs/2Wyne8l2+b7HCliT4lHlAANtUKP0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=r1eviRHifDhzFR62Rl4Hl0Fldbxi2i1iUnRJ7++2aGuq32uA+sAcMmBxT7j5wcxja Dr3ZCuEdjdi8uHutObrIAwF0D3hmur8+G1xnxQFbAKkLNL4iYe27x5IIXBJBjwF3Xn rMjfwIIGVLgiU6ulekobGpCWlb6zkHltfsa8SzERy2qg6tWRTjshCJLTGPZ6wuTwwQ OCQ9I8WFX1h1b3KktdQHU34zpodV9N9zEu3H1biShZL/3tZAdlnkgltMswqALaTjxE eX9ysZSrrbzj1mt2R0c9c7jXa5m9WR8iNE2m/RO3JX7xMzNFbmQ7RIqHovhYcsURJu lOX2pHSd5VFlQ== Message-ID: Date: Wed, 19 Nov 2025 10:17:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/9] mm: introduce copy-on-fork VMAs and make VM_MAYBE_GUARD one To: Lorenzo Stoakes , Andrew Morton Cc: Jonathan Corbet , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jann Horn , Pedro Falcato , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrei Vagin References: <5d41b24e7bc622cda0af92b6d558d7f4c0d1bc8c.1763460113.git.lorenzo.stoakes@oracle.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <5d41b24e7bc622cda0af92b6d558d7f4c0d1bc8c.1763460113.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 03531140015 X-Stat-Signature: 7opkq6ms9esi7mxpyeggcsrdazjte9uu X-Rspam-User: X-HE-Tag: 1763543845-860622 X-HE-Meta: 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 n6BPZeDd WD5vnBG+TGpE/gxfnG2DfPfXL2SrKjDA3xUG7XSFpP3onmd4R7LAZyHjz8fV4OvYD7Fyg926bp443BwfSSvqXAsbAYYP1brKOh+fyREeeRmzvaRgts+bj+jYNRq6BOZNjs/cJZDfp6rKaI/ook89hQx07HStunNcjl/01pXWdqUUiYl/v8XElNUkagI+tpo1ZxvajCCPdI+pHDbm6CrAeEXcTHAihhWfN++TDemHcQLBBMXmA4XtxlxqZRLtYHTBtX4yt5vUWz1wbQZyCbowRm7kL0N2Pg41EsOQhfXrYFYteJYnNtSZcsaQ+ldMhAzTnJtraV7bvl0aQw/3h+mO74nzXAEtaE8AbdvN9 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 18.11.25 11:17, Lorenzo Stoakes wrote: > Gather all the VMA flags whose presence implies that page tables must be > copied on fork into a single bitmap - VM_COPY_ON_FORK - and use this > rather than specifying individual flags in vma_needs_copy(). > > We also add VM_MAYBE_GUARD to this list, as it being set on a VMA implies > that there may be metadata contained in the page tables (that is - guard > markers) which would will not and cannot be propagated upon fork. > > This was already being done manually previously in vma_needs_copy(), but > this makes it very explicit, alongside VM_PFNMAP, VM_MIXEDMAP and > VM_UFFD_WP all of which imply the same. > > Note that VM_STICKY flags ought generally to be marked VM_COPY_ON_FORK too > - because equally a flag being VM_STICKY indicates that the VMA contains > metadat that is not propagated by being faulted in - i.e. that the VMA > metadata does not fully describe the VMA alone, and thus we must propagate > whatever metadata there is on a fork. > > However, for maximum flexibility, we do not make this necessarily the case > here. > > Signed-off-by: Lorenzo Stoakes > Reviewed-by: Pedro Falcato > Reviewed-by: Vlastimil Babka > --- Acked-by: David Hildenbrand (Red Hat) -- Cheers David