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 1F9B5478E44 for ; Fri, 27 Feb 2026 20:57:06 +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=1772225827; cv=none; b=Q4nk0JefWKzLlJpOg8a9Oyu9OZLqzAkxub9rCI/Np9LQYQ5WnAQcB2uG4kcO2xOA60LX9yj6RggbB+9/c8KUNntEk5jeY42BJm1di9ugpb8inz1hHkTtoaSxGxsAYiyOEu16PwUQGph5TieOXN7m+EKa0466rrHCcNz92MqXNcw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772225827; c=relaxed/simple; bh=jN++5+fyopK0ebaI0/tN+FMCYIwdoX+CiSE5DAc+JMQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NE8xY8zdJ8jEDC47VFolqFY2HUDAyOPoD29CuHLy8vi6kxy7KFaINW1SuK2UGwC3chqVBPTeIkRXXVVnzd7rkXNSDxkM8/xHnyiDYCoCTK/Q0QyZQnPKvdS0Y/8wYYclWnXy/96D2KsZHrJXPrQLvqw38zuuDF4s9cnKVeVnY34= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iahY6J2z; 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="iahY6J2z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57B82C116C6; Fri, 27 Feb 2026 20:57:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772225826; bh=jN++5+fyopK0ebaI0/tN+FMCYIwdoX+CiSE5DAc+JMQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iahY6J2zr+FK7pIkam758ib/IzAkZgx1/9bB/UUWqkE98qH1vXV0fLHroGZJN43sm /otn4HZQEvxaSLhGfNvFm5WIDr947JvTf2AoGEkp6z8fk4osfrxg54NP0hUssco3uT cMSmolOPEF9tVR/2y3G85Luv/4RPh4ACOTVQfqVR9yYqhRzKhDGNeiS3NeoVW6Y2gt pD9VQKi5xLqz5gipcWs9XbHGj8jmoRZbACvFrHYKlLfqlAvQcE/mB0YLFWPPEGOaeJ mUpUKgn1JyJxyGUcW54k8oyhbUoR/VmbjCVhN96Kv/oxrrjT/80poBfUV1S18TB8hH OpiSbPkHKF5Xw== Message-ID: <4f512562-1fed-454e-aca3-2e1a257c28b0@kernel.org> Date: Fri, 27 Feb 2026 21:57:01 +0100 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 v2] khugepaged: remove redundant index check for pmd-folios To: Dev Jain , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260227143501.1488110-1-dev.jain@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/27/26 15:35, Dev Jain wrote: > Claim: folio_order(folio) == HPAGE_PMD_ORDER => folio->index == start. > > Proof: Both loops in hpage_collapse_scan_file and collapse_file, which > iterate on the xarray, have the invariant that > start <= folio->index < start + HPAGE_PMD_NR ... (i) > > A folio is always naturally aligned in the pagecache, therefore > folio_order == HPAGE_PMD_ORDER => IS_ALIGNED(folio->index, HPAGE_PMD_NR) == true ... (ii) > > thp_vma_allowable_order -> thp_vma_suitable_order requires that the virtual > offsets in the VMA are aligned to the order, > => IS_ALIGNED(start, HPAGE_PMD_NR) == true ... (iii) > > Combining (i), (ii) and (iii), the claim is proven. > > Therefore, remove this check. > While at it, simplify the comments. > > Signed-off-by: Dev Jain > --- There might be some conflict with Nicos changes. Acked-by: David Hildenbrand (Arm) -- Cheers, David