From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 340363596EB; Wed, 29 Oct 2025 19:50:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761767425; cv=none; b=lq160BUIh/Od9M8cmFk+KFq0uwQn1lkmNawbLcue/W429MOX4TLm6uIHQcBWW4G3dhDQnu3u9vkfL/zpD5saAnLX4D1pLEb5T0McWsSkqjO58vkB8A/3kZtJk3hrXdf/lhUIwZngybpFqgfZu8+OWhWR+Y6PwYZ6PVsMD9O0+dw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761767425; c=relaxed/simple; bh=x2OAfwS5H+/pyr4WR+Khtf97dsVmyBOZ4UxVwpJdZjo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lgwpfCKlA51ewHVnqTVmsk1UFWfsG1+Zk91lKZN7CTh5/nmU1sx2QpbB/suqQcYvXHopnniD4WVRQ/d4TLjE8jeJlvyk9xwlwY6zuFTNfqMs0QMA5a7N46+dRm47+xwpxNHlDggNjVJmi9iFOS3KCz8/97EQBD9Fe7rKI+G2WN0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=IaH0WiB+; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IaH0WiB+" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Sender:Reply-To:Content-ID:Content-Description; bh=ywMRa9td/qLYvz0QLFt/dHlJeUkQz4iWrYlNlCayuSE=; b=IaH0WiB+Bb8bae/n25tIQisGQE EwhH0nUvAY0WF68tV+bqAjeM5vt1+TFM+p9SWhDN7SSKHd71InQaX+spzoIsKsfRnYzLiPymBfv8b G0YUSVRmmHR72tbVjz7S1JCp1h94cR+krcxjkfnjWvoj0qzTCwutfhbayHRtPzVCrp4DBQP6QMP7E /5l7sL8Z4TbLmfGLBzrYSVUcbZopibwGw10l95Xv2hyvw2OljCjZDfVaA7JzI0kxcTG+eF758lStl ZwIQstpTPU88RRMUCb5P0e0hsxC1roRLf9JTHYYZ9gSRvYXs7n8ZIZ62F6HWHDjILexzwXgNL7cbg SLWmox1g==; Received: from [50.53.43.113] (helo=[192.168.254.34]) by bombadil.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vECBX-00000002fGY-0vOJ; Wed, 29 Oct 2025 19:50:19 +0000 Message-ID: <6c273611-e815-4a4a-822d-f6e55cec3810@infradead.org> Date: Wed, 29 Oct 2025 12:50:18 -0700 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] mm: introduce VM_MAYBE_GUARD and make visible for guard regions To: Lorenzo Stoakes , Andrew Morton Cc: Jonathan Corbet , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jann Horn , Pedro Falcato , 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: <7de40603015dee82970f5d37332a6d5af7532063.1761756437.git.lorenzo.stoakes@oracle.com> Content-Language: en-US From: Randy Dunlap In-Reply-To: <7de40603015dee82970f5d37332a6d5af7532063.1761756437.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/29/25 9:50 AM, Lorenzo Stoakes wrote: > diff --git a/mm/memory.c b/mm/memory.c > index 4c3a7e09a159..a2c79ee43d68 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1478,6 +1478,10 @@ vma_needs_copy(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) > if (src_vma->anon_vma) > return true; > > + /* Guard regions have momdified page tables that require copying. */ modified > + if (src_vma->vm_flags & VM_MAYBE_GUARD) > + return true; > + > /* > * Don't copy ptes where a page fault will fill them correctly. Fork > * becomes much lighter when there are big shared or private readonly -- ~Randy