From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755608Ab0JVI3e (ORCPT ); Fri, 22 Oct 2010 04:29:34 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:33375 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753925Ab0JVI3d (ORCPT ); Fri, 22 Oct 2010 04:29:33 -0400 Date: Fri, 22 Oct 2010 04:29:16 -0400 From: Christoph Hellwig To: Jens Axboe Cc: Jeremy Fitzhardinge , Andreas Dilger , "Theodore Ts'o" , Linux Kernel Mailing List , "Xen-devel@lists.xensource.com" Subject: Re: linux-next regression: IO errors in with ext4 and xen-blkfront Message-ID: <20101022082916.GA14070@infradead.org> References: <4CBF83A0.8090802@goop.org> <4CBF84C9.6050606@goop.org> <4CC148E5.2030605@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4CC148E5.2030605@kernel.dk> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the barriers tree Xen claims to support flushes, but I doesn't. It never handles REQ_FLUSH requests. Try commenting out the blk_queue_flush(info->rq, info->feature_flush); call and things should improve. I still need to hear back from Xen folks how to actually implement a cache flush - they only implement a barrier write privilegue which could never implement an empty cache flush. Up to current kernels that meant it would implement barrier writes with content correctly and silently ignore empty barriers leading to very interesting data integrity bugs. From 2.6.37 onwards it simply won't work anymore at all, which is at least consistent (modulo the bug of actually claiming to support flushes).