From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH v2] block: do not artificially constrain max_sectors for stacking drivers Date: Mon, 9 Jul 2012 18:57:25 -0400 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 Return-path: Content-Disposition: inline In-Reply-To: <20120709145711.GB30886@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: "Chauhan, Vijay" Cc: axboe@kernel.dk, "Martin K. Petersen" , linux-kernel@vger.kernel.org, "Stankey, Robert" , "Moger, Babu" , "dm-devel@redhat.com" List-Id: dm-devel.ids 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