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 80850CFC28D for ; Fri, 21 Nov 2025 16:09:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A6C256B0022; Fri, 21 Nov 2025 11:09:23 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A1D8E6B002B; Fri, 21 Nov 2025 11:09:23 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 90C6A6B002D; Fri, 21 Nov 2025 11:09:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 7B49B6B0022 for ; Fri, 21 Nov 2025 11:09:23 -0500 (EST) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id B8A38130277 for ; Fri, 21 Nov 2025 16:09:20 +0000 (UTC) X-FDA: 84135098880.23.2619746 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf08.hostedemail.com (Postfix) with ESMTP id DE7E0160015 for ; Fri, 21 Nov 2025 16:09:18 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=DXrPBIfz; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763741359; a=rsa-sha256; cv=none; b=3jYSjHI8jBR89cKmO+w+Odim8r3v/FFFprFs2X1TJ7dggqfxW6cNHQe0jbSmTT7DO9UrnM X+GUmB8jVFgJg1dzZSJx/DEBK/BF35z4ro4dBRIHqM5fyf45zVGWBybTGYsqXnJLz3ZlwH g5dZCX4BAVDr1Z0qL5cnIF8dIm+0z3U= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=DXrPBIfz; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763741359; 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=ePW388oklA7FMns8MHWa6eByXoeTMRetMmV1+DxnMiQ=; b=absupK4IpOMU6DJi6ZmxyGee3O0g+UfX/cyO/7+P/+rYn1WYaNzpLNRltSPetwOx8rb+ji jpdpMSEUBQJbVrdzjwsJ1eMSCEgVCsfhwfocAonkap4tKHQkuoG81jWTOAz6H3abu+ZCXp ddMZJ+V+0AHzGMatDUq9yqz5KcVNtkI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 89BC843E4B; Fri, 21 Nov 2025 16:09:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7E86C4CEF1; Fri, 21 Nov 2025 16:09:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763741357; bh=//OuOvMXeDV9xgqjwXYfwljPeKEYUBLLHfpTkq6K8+8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=DXrPBIfzI0rxVmeV3dm4FH1BWca0aQOsApup4El5ebC7/Wnbgl4eKyhSn1TIGGat+ vzz/NrU+jaItZ8HFmGhr86j1xgwmOSYZSNYke4wL/syHqsVWZQukAqEhNqa+YNeBPk 31QsKCYCoAkM38ieBYVKK5PUc7SbGf1eklyzn4hbLVOVv03psyu/FsTvwpQUJc32fZ 7tY90oZuYPnRk61KoNosla/msm9JvWELMKFOGQibL0zU59vuJTMgJueCkMx3/vpyuS 7FE3P69FI738zFjFu+4J6UR3L8bSD7oVpcGOKZ1Fj9BmljA4Dxgutytafxy0PEhDdT FX70hzkqbeyzw== Message-ID: Date: Fri, 21 Nov 2025 17:09:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/9] mm: implement sticky VMA flags 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: <22ad5269f7669d62afb42ce0c79bad70b994c58d.1763460113.git.lorenzo.stoakes@oracle.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <22ad5269f7669d62afb42ce0c79bad70b994c58d.1763460113.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DE7E0160015 X-Stat-Signature: jzb3ws3ywpx176j8gniwd76hprrkcant X-HE-Tag: 1763741358-452854 X-HE-Meta: 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 P3Oj7gms mY1LJwrNxVh5lSW6LoLHrYdoieFdc4JzLwEVDH0KoQiBaH5/Alz5iJ/g+PIJyml/DroEMveHmpd6sGx7r9+T0pgOb63aCPEMndQNeJzFYfkHvN1+5HLQPTe3aaIwhLe5p32JyPwevXvWmy1z2JJV707FciM2dMSHpz+Fz3LGoD2PI31OWPyf6UhwBm+Xp+zKa3xAHkY9hZUmjGFpl9qFpBs1w90/k+0oDMLmYaHOiaeixB3ao+xIWHjv8H/bindeULJyygvVfmvC7cMimjCFyoixJEDRCcan3jxrb7fRkDDgrqGcbjQK6rQMyBQ== 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 11/18/25 11:17, Lorenzo Stoakes wrote: > It is useful to be able to designate that certain flags are 'sticky', that > is, if two VMAs are merged one with a flag of this nature and one without, > the merged VMA sets this flag. > > As a result we ignore these flags for the purposes of determining VMA flag > differences between VMAs being considered for merge. > > This patch therefore updates the VMA merge logic to perform this action, > with flags possessing this property being described in the VM_STICKY > bitmap. > > Those flags which ought to be ignored for the purposes of VMA merge are > described in the VM_IGNORE_MERGE bitmap, which the VMA merge logic is also > updated to use. > > As part of this change we place VM_SOFTDIRTY in VM_IGNORE_MERGE as it > already had this behaviour, alongside VM_STICKY as sticky flags by > implication must not disallow merge. > > Ultimately it seems that we should make VM_SOFTDIRTY a sticky flag in its > own right, but this change is out of scope for this series. > > The only sticky flag designated as such is VM_MAYBE_GUARD, so as a result > of this change, once the VMA flag is set upon guard region installation, > VMAs with guard ranges will now not have their merge behaviour impacted as > a result and can be freely merged with other VMAs without VM_MAYBE_GUARD > set. > > Also update the comments for vma_modify_flags() to directly reference > sticky flags now we have established the concept. > > We also update the VMA userland tests to account for the changes. > > Signed-off-by: Lorenzo Stoakes > Reviewed-by: Pedro Falcato > Reviewed-by: Vlastimil Babka > --- Acked-by: David Hildenbrand (Red Hat) -- Cheers David