From: Eric Sandeen Subject: Re: [PATCH 4/4] ext4: call blkdev_issue_flush on fsync Date: Tue, 20 May 2008 10:52:38 -0500 Message-ID: <4832F3C6.1050601@redhat.com> References: <482DDA56.6000301@redhat.com> <482DDC04.7020706@redhat.com> <20080520023454.GM15035@mit.edu> <20080520154313.GI16676@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: Theodore Tso , Eric Sandeen , ext4 development , linux-kernel Mailing List , linux-fsdevel Return-path: Received: from mx1.redhat.com ([66.187.233.31]:58314 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754039AbYETPxD (ORCPT ); Tue, 20 May 2008 11:53:03 -0400 In-Reply-To: <20080520154313.GI16676@shareable.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Jamie Lokier wrote: > Theodore Tso wrote: >> On Fri, May 16, 2008 at 02:09:56PM -0500, Eric Sandeen wrote: >>> To ensure that bits are truly on-disk after an fsync, >>> we should call blkdev_issue_flush if barriers are supported. >> This patch isn't necessary, and in fact will cause a double flush. >> When you call fsync(), it calls ext4_force_commit(), and we do a the >> equivalent of a blkdev_issue_flush() today (which is what happenes >> when you do a submit_bh(WRITE_BARRIER, bh), which is what setting >> set_ordered_mode(bh) ends up causing. > > ISTR fsync() on ext3 did not always force a commit, if in-place data > writes did not change any metadata. I think that might still be true, but I'm still looking through it (in the background...) I tried blktrace to see what was going on but I'm not sure what an "NB" in the RWBS field means, anyone know? -Eric