Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756527Ab1EJOtt (ORCPT ); Tue, 10 May 2011 10:49:49 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46192 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754062Ab1EJOtr (ORCPT ); Tue, 10 May 2011 10:49:47 -0400 Date: Tue, 10 May 2011 16:49:39 +0200 From: Jan Kara To: OGAWA Hirofumi Cc: Christoph Hellwig , "Darrick J. Wong" , Theodore Tso , Jan Kara , 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 Subject: Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses Message-ID: <20110510144939.GI4402@quack.suse.cz> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <874o524q9h.fsf@devron.myhome.or.jp> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1829 Lines: 36 On Tue 10-05-11 22:52:10, OGAWA Hirofumi wrote: > Christoph Hellwig writes: > > > On Tue, May 10, 2011 at 10:59:15AM +0900, OGAWA Hirofumi wrote: > >> I'd like to know those patches are on what state. Waiting in writeback > >> page makes slower, like you mentioned it (I guess it would more > >> noticeable if device was slower that like FAT uses). And I think > >> currently it doesn't help anything others for blk-integrity stuff > >> (without other technic, it doesn't help FS consistency)? > > > > It only makes things slower if we rewrite a region in a file that is > > currently undergoing writeback. I'd be interested to know about real > > life applications doing that, and if they really are badly affect we > > should help them to work around that in userspace, e.g. by adding a > > fadvice will rewrite call that might be used to never write back that > > regions without an explicit fsync call. > > 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. 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. 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. Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/