From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752733Ab2GIW5m (ORCPT ); Mon, 9 Jul 2012 18:57:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36842 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751184Ab2GIW5l (ORCPT ); Mon, 9 Jul 2012 18:57:41 -0400 Date: Mon, 9 Jul 2012 18:57:25 -0400 From: Mike Snitzer To: "Chauhan, Vijay" Cc: axboe@kernel.dk, "Martin K. Petersen" , linux-kernel@vger.kernel.org, "Stankey, Robert" , "Moger, Babu" , "dm-devel@redhat.com" Subject: Re: [PATCH v2] block: do not artificially constrain max_sectors for stacking drivers Message-ID: <20120709225725.GA1487@redhat.com> References: <20120709130052.GC30048@redhat.com> <20120709131611.GD30048@redhat.com> <20120709134041.GA30633@redhat.com> <20120709141416.GB30633@redhat.com> <20120709145711.GB30886@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120709145711.GB30886@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 09 2012 at 10:57am -0400, Mike Snitzer wrote: > blk_set_stacking_limits() is intended to allow stacking drivers to build > up the limits of the stacked device based on the underlying devices' > limits. But in the case of 'max_sectors' the default of > BLK_DEF_MAX_SECTORS (1024) doesn't allow the stacking driver to inherit > a max_sectors larger than 1024. > > It is now clear that this artificial limit is getting in the way so > change blk_set_stacking_limits's max_sectors to UINT_MAX (which allows > stacking drivers like dm-multipath to inherit 'max_sectors' from the > underlying paths). > > blk_limits_max_hw_sectors() must allow stacking drivers to not have > max_sectors set to BLK_DEF_MAX_SECTORS as a side-effect. Move that > historic constraint to blk_queue_max_hw_sectors(). > > Reported-by: Vijay Chauhan > Signed-off-by: Mike Snitzer > Cc: Martin K. Petersen > --- > block/blk-settings.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > v2: tweak blk_limits_max_hw_sectors and blk_queue_max_hw_sectors As it happens, v2's changes to blk_limits_max_hw_sectors and blk_queue_max_hw_sectors are not strictly required in order for existing stacking drivers to have have an unconstrained max_sectors. Dropping those changes also allows for consistency across both block functions. So I'd be happy if v1 were to be staged for 3.6. NetApp: it would be great if you could confirm that v1 does in fact address the max_sectors issue you reported. Thanks, Mike