From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (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 315E5199A2 for ; Tue, 19 Dec 2023 13:48:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0Vyr8pAw_1702993704; Received: from 192.168.71.120(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0Vyr8pAw_1702993704) by smtp.aliyun-inc.com; Tue, 19 Dec 2023 21:48:25 +0800 Message-ID: Date: Tue, 19 Dec 2023 21:48:24 +0800 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/5] btrfs: use the super_block as holder when mounting file systems To: Christoph Hellwig Cc: Chris Mason , Josef Bacik , David Sterba , "linux-btrfs@vger.kernel.org" , Christian Brauner , Eric Biggers , Johannes Thumshirn References: <20231218044933.706042-1-hch@lst.de> <20231218044933.706042-6-hch@lst.de> <04e599b9-5d6d-4ac0-bf74-da9bedfb585f@wdc.com> <20231218150234.GB19041@lst.de> <5dc7ecdd-8bd3-4016-b8da-49ff306bcd3c@linux.alibaba.com> <20231219121911.GA21959@lst.de> From: Gao Xiang In-Reply-To: <20231219121911.GA21959@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2023/12/19 20:19, Christoph Hellwig wrote: > On Tue, Dec 19, 2023 at 01:33:54PM +0800, Gao Xiang wrote: >>>> ext4, f2fs and xfs use the super_block, erofs uses 'sb->s_type' as well >>>> here. Reiser uses the journal and so does jfs. So while these two might >>>> not be the best examples in the world, all other is an exaggeration. >>> >>> As of 6.8-rc every file system but btrfs should be using the superblock. >> >> Just saw this by chance. Currently EROFS uses 'sb->s_type' to refer >> external binary source devices (blobs) across different mounts. Since >> these devices are treated readonly so such external sources can be >> shared between mounts as some shared data layer. > > Makes sense for that somewhat unusual use case. Note that this means > you can't really use blk_holder_ops based notifications from the block > driver, but for read-only devices that's not all that important anyway. Yeah, anyway even if notifications is used in the future, I will think more about this later. Thanks, Gao Xiang