From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [Xen-devel] Re: [patch] xen-blkback: sync I/O after backend disconnected Date: Mon, 15 Aug 2011 11:10:42 -0400 Message-ID: <20110815151042.GA22541@dumpdata.com> References: <4E48A6A6.4040706@oracle.com> <20110815144610.GA3707@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20110815144610.GA3707@infradead.org> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: Joe Jin , "xen-devel@lists.xensource.com" , Jens Axboe , Greg Marsden , "linux-kernel@vger.kernel.org" , Ian Campbell , Kurt C Hackel List-Id: xen-devel@lists.xenproject.org On Mon, Aug 15, 2011 at 10:46:10AM -0400, Christoph Hellwig wrote: > On Mon, Aug 15, 2011 at 12:55:02PM +0800, Joe Jin wrote: > > When backend disconnect, sync IO requests to the disk. > > Care to explain why? I was thinking it might be a good idea to do that when a disk (file, LVM, real block device) is released from a guest just in case there is some outstanding I/Os. But then I realized that we bypasses the page cache anyhow - so there should be no outstanding I/O requests - unless they are in the disk queue. And the guest would normally issues a FLUSH when unmounting the disk. Hm, I wonder what the conditions are when we forcibly kill the guest - there might be outstanding I/Os in the disk's cache - at which point we should probably sync the write cache, no? > > Also you'll just need a sync_blockdev, fsync_bdev does far to many > things that don't make any sense when you don't have a file system > mounted on a device. > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel