From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-116.mta1.migadu.com [95.215.58.116]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5CEAB3AF66E for ; Mon, 21 Sep 2026 08:20:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.116 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789978840; cv=none; b=JD3w3Qt7u0EQHD0CoW0QKbfg2dVgyYYt14JYOhI2pFhElHyYlL6BhO9gzB6Yltn7hAPijmZ0ALZOCdLCpEJPiVzDsUlSnIBLqAr7NcEghMPONYLmU4m/+1klV3ITzDyO8kf/fMwxf0YzIV3vedF33ZKObNhrCi8Zcf1d341jXo0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789978840; c=relaxed/simple; bh=aoprAUYmUN2jwm3AkI2t0iJil/x7yD8M/lNnyU1MNmM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=k2pCsHs9GTynq88pzktWRP0tWKiCFVdgaJ2y04b4c6IOHHDCAz5a04fiMZVMf5VV9/CBjzsBzMhGu7RNH8EdZzNAFeH5frKJ3CWffHWv2k/uSl10czY7qf4R+iAI4EqDQo6z5+HUT8qmV/0G1wT2yHb+2EWQYdkjeHlxrJz+hu4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=pbnXMYd1; arc=none smtp.client-ip=95.215.58.116 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="pbnXMYd1" X-Envelope-To: linux-fsdevel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=aoprAUYmUN2jwm3AkI2t0iJil/x7yD8M/lNnyU1MNmM=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789978836; v=1; x=1790583636; b=pbnXMYd1TTDYxvKVuHEhnHM68i5nflXaGYTg/MAPcW5x241s8L2cTE6Cg4McgY82bnXkB9BN Ds2WIlCp8hucVQ1jbqb8NZNGL43WzXy7dsPIDjJXTdF9/N3ZfhV/JkzxgPm3TtHHXmyJNA1gcNC CGyqPD3c+oF929v1pvjwUUyg= X-Envelope-To: linux-fsdevel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 3d02c4ea80ac0ea7; Mon, 21 Sep 2026 08:20:20 +0000 X-Mizu-Trace-ID: 3d02c4ea80ac0ea7 X-Migadu-Flow: FLOW_OUT Message-ID: <86f06c26-5318-4196-b792-0662ad64f2bf@linux.dev> Date: Mon, 21 Sep 2026 16:20:01 +0800 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 v5 08/17] erofs: mm/pagemap: add readahead_folio_last() to avoid folio->private Content-Language: en-US To: Zi Yan Cc: linux-mm@kvack.org, David Hildenbrand , Dev Jain , Usama Arif , Gregory Price , linux-kernel@vger.kernel.org, Muchun Song , Gao Xiang , Chao Yu , Ryan Roberts , "Matthew Wilcox (Oracle)" , Jan Kara , Mike Rapoport , Nico Pache , Baolin Wang , Lorenzo Stoakes , Michal Hocko , Qi Zheng , Yue Hu , Jeffle Xu , Sandeep Dhavale , Shakeel Butt , Alistair Popple , Johannes Weiner , Hongbo Li , Kairui Song , "Liam R. Howlett" , Chunhai Guo , linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, Ying Huang , Barry Song , Suren Baghdasaryan , Vlastimil Babka , Andrew Morton References: <20260920-remove-pg_private-v5-0-bb68b6a21869@nvidia.com> <20260920-remove-pg_private-v5-8-bb68b6a21869@nvidia.com> From: Lance Yang In-Reply-To: <20260920-remove-pg_private-v5-8-bb68b6a21869@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2026/9/21 10:28, Zi Yan wrote: > erofs needs to traverse readahead folios in reverse order to achieve > maximum performance by > 1. reading all folios from readahead_folio(); > 2. storing the prior folio pointer in folio->private; > 3. traverse from the last folio to the first one. > > Add readahead_folio_last() to achieve the same function without using > folio->private. __readahead_advance() helper shares readahead_control > adjustment code among __readahead_folio(), readahead_folio_last(), and > __readahead_batch() by checking new private member, _forward, of > readahead_control. > > It prepares for a future commit that replaces PG_private checks with > !folio->private checks. After switching the checks, erofs's use of > folio->private without bumping folio refcount can cause unexpected > outcomes, e.g., in filemap_release_folio(), try_to_free_buffers() becomes > reachable. > > No functional change intended. > > Assisted-by: LLM > To: Gao Xiang > To: Chao Yu > To: "Matthew Wilcox (Oracle)" > To: Jan Kara > Cc: Yue Hu > Cc: Jeffle Xu > Cc: Sandeep Dhavale > Cc: Hongbo Li > Cc: Chunhai Guo > Cc: linux-erofs@lists.ozlabs.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-fsdevel@vger.kernel.org > Cc: linux-mm@kvack.org > Acked-by: David Hildenbrand (Arm) > Signed-off-by: Zi Yan > --- Nothing jumped out at me, feel free to add: Reviewed-by: Lance Yang