From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752852AbcAUWzL (ORCPT ); Thu, 21 Jan 2016 17:55:11 -0500 Received: from mga01.intel.com ([192.55.52.88]:24396 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751113AbcAUWv3 (ORCPT ); Thu, 21 Jan 2016 17:51:29 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,327,1449561600"; d="scan'208";a="33873715" Date: Thu, 21 Jan 2016 22:51:27 +0000 From: Keith Busch To: Jens Axboe Cc: Stefan Haberland , torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Sebastian Ott Subject: Re: [BUG] Regression introduced with "block: split bios to max possible length" Message-ID: <20160121225127.GA30993@localhost.localdomain> References: <56A0F1CA.4010303@linux.vnet.ibm.com> <56A14EE4.1020008@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56A14EE4.1020008@fb.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 21, 2016 at 02:34:28PM -0700, Jens Axboe wrote: > On 01/21/2016 07:57 AM, Stefan Haberland wrote: > >Hi, > > > >unfortunately commit e36f62042880 "block: split bios to maxpossible length" > >breaks the DASD driver on s390. We expect the block requests to be > >multiple > >of 4k in size. With the patch applied I see the requests split up in > >multiple > >of 512 byte and therefore the requests get rejected and lots of I/Os fail. > > Sigh, that's definitely a bug. I'll take a look at it and see if I > can get a tested fix in for 4.5-rc1. If not, we'll revert it, again. My apologies for the trouble. I trust it really is broken, but I don't quite see how. The patch supposedly splits the transfer to the max size the request queue says it allows. How does the max allowed size end up an invalid multiple?