Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933705AbaJHWM1 (ORCPT ); Wed, 8 Oct 2014 18:12:27 -0400 Received: from mail-ig0-f169.google.com ([209.85.213.169]:63979 "EHLO mail-ig0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933687AbaJHWMZ (ORCPT ); Wed, 8 Oct 2014 18:12:25 -0400 Message-ID: <5435B6C0.8020704@kernel.dk> Date: Wed, 08 Oct 2014 16:12:16 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 To: Mike Snitzer , linux-kernel@vger.kernel.org CC: martin.petersen@oracle.com, dm-devel@redhat.com Subject: Re: [PATCH] block: fix alignment_offset math that assumes io_min is a power-of-2 References: <1412805952-15316-1-git-send-email-snitzer@redhat.com> In-Reply-To: <1412805952-15316-1-git-send-email-snitzer@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/08/2014 04:05 PM, Mike Snitzer wrote: > The math in both blk_stack_limits() and queue_limit_alignment_offset() > assume that a block device's io_min (aka minimum_io_size) is always a > power-of-2. Fix the math such that it works for non-power-of-2 io_min. > > This issue (of alignment_offset != 0) became apparent when testing > dm-thinp with a thinp blocksize that matches a RAID6 stripesize of > 1280K. Commit fdfb4c8c1 ("dm thin: set minimum_io_size to pool's data > block size") unlocked the potential for alignment_offset != 0 due to > the dm-thin-pool's io_min possibly being a non-power-of-2. Well that sucks, AND with a mask is considerably cheaper than a MOD... -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/