From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DCEBA1B81CA for ; Sun, 19 Apr 2026 08:20:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776586808; cv=none; b=IaGGtCKL4l6y1PUKcNkCqUplWIS/E/W9Xx3mldlNqXgAXFFFGOG5DK7RJeN8cD/o8AWDGq0lX1b5d8XC9YlBo4j2e1ZGec2K+BFpiRnV/cs1Z10D7fY5u+ldNDU70o3pqYRC8mbYlasxDrJAX9aGWqjvJ54pj8wLqig6y+WWkNA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776586808; c=relaxed/simple; bh=ULzAcQ+a5yvU6pSydPbcp5Zrd7MaFUBLpohDNl0zto0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XjI2p4U0MR3I5axg4umsw3pXkxmTkM7/xenW5ikckIt+q0eAppolXROT6AHcobY5yJJanvxdbbk6TbQagvEf4ixflov6qGwYQT0RqAWhCCrAenyJDd5WN4+X7dhwfXICQifhRWmxU1LfbcnCL6aEe5YJaWIW8ybSHCYJNO0LJ1g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jY1BPD2l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jY1BPD2l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC0B7C2BCAF; Sun, 19 Apr 2026 08:20:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776586808; bh=ULzAcQ+a5yvU6pSydPbcp5Zrd7MaFUBLpohDNl0zto0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=jY1BPD2lU1Iqz7fd/hrVI4VR2mnaRy7YSp0qiFqQOF0egxnj5OfsXl3VHc08ncjvI asjBFqyyeELe0U0CCDnkgUJR0mODASwcvBUzKoES8ge/b+a1qZvz3iIetDqro/3YDu Zg02sSy2I3l4Su32OyEciZ0z5J59oy8kplSRsUYomBpiTdD3/Q1nwPqfACTsEAVV4p XZf2q3y2Jd1WUC5Ufo9hi9pJ9nEb1SUQnEOr/PpZKBHbOxRBnCR9+gax7lR7xAtGwR Z+POE2aqz4butePJg6YNOjC5/d+6Na02UjwzpBHf2MdIdClFBq6oINoybXTMYCZ17B JlqfByBVk1D3Q== Message-ID: <7b983108-4846-46ce-b9f5-2aef319c00dd@kernel.org> Date: Sun, 19 Apr 2026 10:19:59 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: prepare anon_vma before swapin rmap To: Lorenzo Stoakes Cc: ZhengYuan Huang , akpm@linux-foundation.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, r33s3n6@gmail.com, zzzccc427@gmail.com References: <20260417011606.1089985-1-gality369@gmail.com> <66f67e51-819b-4c60-9f61-170db32362a2@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/18/26 11:35, Lorenzo Stoakes wrote: > On Fri, Apr 17, 2026 at 01:57:59PM +0200, David Hildenbrand (Arm) wrote: >> Maybe there was a scenario where we could have lost vma->anon_vma during >> a merge, resulting in a swapped page in an anon_vma. > > Unless there's a bug (and correct me if I'm misinterpreting), VMA merge requires > vma->anon_vma to either be equal for merged adjacent VMAs, or one or the other > VMA to have NULL vma->anon_vma, in which case we set vma->anon_vma in the merged > VMA. I think you didn't understand what I was trying to say. The reporter claimed that it happened on 6.18. Nobody knows on which patch version (stable tree?). I was wondering whether your fix commit 3b617fd3d317bf9dd7e2c233e56eafef05734c9d Author: Lorenzo Stoakes Date: Mon Jan 5 20:11:49 2026 +0000 mm/vma: enforce VMA fork limit on unfaulted,faulted mremap merge too that went into 6.19 might have resolved this problem. Your fix stated "allow an unfaulted/faulted merge with a VMA that has been forked", so I was wondering whether that could have resulted in a situation with anon folios without vma->anon_vma (losing vma->anon_vma during the merge). But I am not sure if 879bca0a2c4f could have triggered that. Are you aware of other fixes that went into 6.19 that could have fixed such a scenario? -- Cheers, David