From: Michal Novotny Subject: Re: [PATCH] extend e2fsprogs functionality to add EXT2_FLAG_DIRECT option Date: Tue, 12 Jan 2010 17:51:18 +0100 Message-ID: <4B4CA886.8070808@redhat.com> References: <4B4B84E2.1050508@redhat.com> <4B4C54DC.4040006@redhat.com> <4B4C6429.6090803@redhat.com> <4B4C67F5.1020009@redhat.com> <20100112122319.GA20596@infradead.org> <4B4C6B70.1050205@redhat.com> <20100112124600.GA7151@infradead.org> <4B4C7297.5030905@redhat.com> <20100112163828.GA14633@infradead.org> <4B4CA6A9.3030401@redhat.com> <20100112164748.GA26895@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Ric Wheeler , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: Christoph Hellwig Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31578 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752453Ab0ALQvr (ORCPT ); Tue, 12 Jan 2010 11:51:47 -0500 In-Reply-To: <20100112164748.GA26895@infradead.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 01/12/2010 05:47 PM, Christoph Hellwig wrote: > On Tue, Jan 12, 2010 at 05:43:21PM +0100, Michal Novotny wrote: > >> So, do you think the problem is in the Xen backend drivers and to make >> it working right in Xen the driver fix is needed? >> > Yes, the Xen blkback driver just submits I/O directly without using > the right interfaces to force cache coherency. It might be relatively > easy to hack a call in to flush all caches when it starts up, but given > how it bypasses all abstractions it's almost impossible to give full > coherency as if using the normal block device interfaces. > > Ok, this way the fix to the drivers should be done. Thanks for your investigation. I just forwarded your reply to other members of my team. Thanks, Michal