From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752244Ab0ILIvK (ORCPT ); Sun, 12 Sep 2010 04:51:10 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:65235 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751842Ab0ILIvG (ORCPT ); Sun, 12 Sep 2010 04:51:06 -0400 Message-ID: <4C8C9175.5030404@oracle.com> Date: Sun, 12 Sep 2010 16:38:13 +0800 From: Tao Ma User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: Tejun Heo CC: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 02/41] block/loop: queue ordered mode should be DRAIN_FLUSH References: <1283509796-1510-1-git-send-email-tj@kernel.org> <1283509796-1510-3-git-send-email-tj@kernel.org> In-Reply-To: <1283509796-1510-3-git-send-email-tj@kernel.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tejun, Just a small qs about this patch. On 09/03/2010 06:29 PM, Tejun Heo wrote: > loop implements FLUSH using fsync but was incorrectly setting its > ordered mode to DRAIN. Change it to DRAIN_FLUSH. In practice, this > doesn't change anything as loop doesn't make use of the block layer > ordered implementation. According to Documentation/block/barrier.txt, QUEUE_ORDERED_DRAIN Requests are ordered by draining the request queue and cache flushing isn't needed. Sequence: drain => barrier QUEUE_ORDERED_DRAIN_FLUSH Requests are ordered by draining the request queue and both pre-barrier and post-barrier cache flushings are needed. Sequence: drain => preflush => barrier => postflush And for loop device, it call fsync in barrier request. See do_bio_filebacked in drivers/block/loop.c bool barrier = !!(bio->bi_rw & REQ_HARDBARRIER); struct file *file = lo->lo_backing_file; if (barrier) { if (unlikely(!file->f_op->fsync)) { ret = -EOPNOTSUPP; goto out; } ret = vfs_fsync(file, 0); if (unlikely(ret)) { ret = -EIO; goto out; } } So actually the sync is done in barrier and no extra flush is needed? Or Do I misread the rules in barrier.txt? Regards, Tao > > Signed-off-by: Tejun Heo > --- > drivers/block/loop.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index f3c636d..c3a4a2e 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -832,7 +832,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, > lo->lo_queue->unplug_fn = loop_unplug; > > if (!(lo_flags& LO_FLAGS_READ_ONLY)&& file->f_op->fsync) > - blk_queue_ordered(lo->lo_queue, QUEUE_ORDERED_DRAIN); > + blk_queue_ordered(lo->lo_queue, QUEUE_ORDERED_DRAIN_FLUSH); > > set_capacity(lo->lo_disk, size); > bd_set_size(bdev, size<< 9);