From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 07/17] vfs: Introduce new helpers for syncing after writing to O_SYNC file or IS_SYNC inode Date: Wed, 26 Aug 2009 14:22:36 -0400 Message-ID: <20090826182236.GA1290@infradead.org> References: <1250697884-22288-1-git-send-email-jack@suse.cz> <1250697884-22288-8-git-send-email-jack@suse.cz> <20090819162638.GE6150@infradead.org> <20090820121531.GC16486@duck.novell.com> <20090820162729.GA24659@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , LKML , Evgeniy Polyakov , ocfs2-devel@oss.oracle.com, Joel Becker , Felix Blyakher , xfs@oss.sgi.com, Anton Altaparmakov , linux-ntfs-dev@lists.sourceforge.net, OGAWA Hirofumi , linux-ext4@vger.kernel.org, tytso@mit.edu To: Jan Kara Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:52953 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802AbZHZSWh (ORCPT ); Wed, 26 Aug 2009 14:22:37 -0400 Content-Disposition: inline In-Reply-To: <20090820162729.GA24659@infradead.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Aug 20, 2009 at 12:27:29PM -0400, Christoph Hellwig wrote: > Maybe you can help brain storming, but I still can't see any way in that > the > > - write data > - write inode > - wait for data > > actually is a benefit in terms of semantics (I agree that it could be > faster in theory, but even that is debatable with todays seek latencies > in disks) Btw, another reason why our current default is actively harmful: barriers With volatile write caches we do have to flush the disk write cache in ->fsync, either implicitly by a metadata operation, or explicitly if only data changed. Unless the filesystems waits itself for the data to hit the disk like XFS or btrfs will be issue the cache flush potentially before the data write has actually reached the disk cache.