From: OGAWA Hirofumi Subject: Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses Date: Wed, 11 May 2011 00:24:58 +0900 Message-ID: <87aaeur31x.fsf@devron.myhome.or.jp> References: <20110509230318.19566.66202.stgit@elm3c44.beaverton.ibm.com> <87tyd31fkc.fsf@devron.myhome.or.jp> <20110510133603.GA5823@infradead.org> <874o524q9h.fsf@devron.myhome.or.jp> <20110510144939.GI4402@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain Cc: Christoph Hellwig , "Darrick J. Wong" , Theodore Tso , Alexander Viro , Jens Axboe , "Martin K. Petersen" , Jeff Layton , Dave Chinner , linux-kernel , Dave Hansen , linux-mm@kvack.org, Chris Mason , Joel Becker , linux-scsi , linux-fsdevel , linux-ext4@vger.kernel.org, Mingming Cao To: Jan Kara Return-path: Received: from mail.parknet.co.jp ([210.171.160.6]:59586 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754009Ab1EJPZG (ORCPT ); Tue, 10 May 2011 11:25:06 -0400 In-Reply-To: <20110510144939.GI4402@quack.suse.cz> (Jan Kara's message of "Tue, 10 May 2011 16:49:39 +0200") Sender: linux-ext4-owner@vger.kernel.org List-ID: Jan Kara writes: >> Isn't it reallocated blocks too, and metadata too? > Reallocated blocks - not really. For a block to be freed it cannot be > under writeback and when it's freed no writeback is started. Sure for data -> data reallocated case. metadata -> data/metadata is still there. > For metadata - yes. But ext3, ext4, xfs, btrfs have to avoid modifying > metadata under writeback anyway (because of journalling / COW > constraints) and thus they don't care. Yes. Those would use better way than just blocking. > For ext2 or vfat it's a different story. But as I wrote to Darrick, > I'm not sure about vfat but for ext2 and similar legacy filesystems, > I'd rather let them live with their unstable pages under IO ;) because > I see a limited use for that. If this patches was not going to tackle it, I have no argument here ;) It would be simply FS specific approach/fixes anymore like journal. Thanks. -- OGAWA Hirofumi