From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:37190) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TQUZz-0000nL-Ow for qemu-devel@nongnu.org; Mon, 22 Oct 2012 22:50:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TQUZy-0002BP-Br for qemu-devel@nongnu.org; Mon, 22 Oct 2012 22:50:55 -0400 Received: from atl4mhob14.myregisteredsite.com ([209.17.115.52]:45680) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TQUZy-0002BK-69 for qemu-devel@nongnu.org; Mon, 22 Oct 2012 22:50:54 -0400 Received: from mailpod.hostingplatform.com (mail.networksolutionsemail.com [205.178.146.50]) by atl4mhob14.myregisteredsite.com (8.14.4/8.14.4) with ESMTP id q9N2oqlS014503 for ; Mon, 22 Oct 2012 22:50:52 -0400 Date: Mon, 22 Oct 2012 19:50:39 -0700 From: Mark Trumpold Message-ID: In-Reply-To: Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit Subject: [Qemu-devel] FW: 'qemu-nbd' explicite flush to disk List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: paolo.bonzini@gmail.com Cc: qemu-devel@nongnu.org Hello Paolo, Before anyone expends any cycles on my last message, I have new information. Today I was able to eliminate the file corruption issue by doing a 'blockdev --flushbufs' prior to taking a snapshot. I haven't done extensive testing yet, but it seems the issue if gone at this point. So sorry for the disruption. Best regards, Mark Trumpold On 10/22/12 8:10 AM, "Mark Trumpold" wrote: >Paolo, > >Please recall you had sent me the link below to a kernel patch to allow >'qemu-nbd' to flush to disk. The patch was applied with good success. > >However, recent testing indicates that filesystem corruption issue I am >seeing seems to be tied to large (>500mbyte) filesystem writes. I also >observe the kernel 'flush' thread approaching 100% cpu at times, and i/o >wait % as reported by 'top' increasing sharply during the copy/write. > >Was wondering if perhaps there are any special kernel config options that >I may be missing for 'nbd', or any other information that might help. > >Best regards, >Mark Trumpold > > >>-----Original Message----- >>From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo >>Bonzini >>Sent: Wednesday, September 12, 2012 11:30 PM >>To: Mark Trumpold >>Cc: qemu-devel@nongnu.org >>Subject: Re: 'qemu-nbd' explicite flush to disk >>Il 12/09/2012 23:28, Mark Trumpold ha scritto: >>> So, I've been experimenting with 'qemu-nbd --cache=writeback ..' >>> This nicely eliminates the 'checkpoint' issue; however, I have as >>> yet been unable to explicitely flush things to disk -- which I would >>>like to >>> do just before a 'nilfs' snapshot. > >>The Linux kernel driver for NBD does not support flushes. Patches were >>sent to the maintainer, but he never applied them. >>You can get them at >>http://thread.gmane.org/gmane.linux.drivers.nbd.general/1108 and try >>them. >>> Subsequently I've been trying to call 'bdrv_co_flush(bs)' directly, >>>but >>>I can't >>figure out how to dereference 'bs' for the call. >>> >>> I'm probably out in the weeds on this one. >>> Any guidance would be greatly appreciated. >>> >>> I am running: >>> qemu-1.2.0 >>> linux kernel 3.3.1 >>> >>> Thank you, >>> Mark Trumpold