From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750927AbWDXHCA (ORCPT ); Mon, 24 Apr 2006 03:02:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750946AbWDXHCA (ORCPT ); Mon, 24 Apr 2006 03:02:00 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:53846 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1750927AbWDXHB7 (ORCPT ); Mon, 24 Apr 2006 03:01:59 -0400 Date: Mon, 24 Apr 2006 09:02:37 +0200 From: Jens Axboe To: David Chinner Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] Direct I/O bio size regression Message-ID: <20060424070236.GD22614@suse.de> References: <20060424061403.GF611708@melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060424061403.GF611708@melbourne.sgi.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 24 2006, David Chinner wrote: > The change introduced here in 2.6.15: > > http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=defd94b75409b983f94548ea2f52ff5787ddb848 > > sets the request queue max_sector size unconditionally to 1024 sectors in > blk_queue_max_sectors() even if the underlying hardware can support a larger > number of sectors. > > Hence when building direct I/O bios, we have the situation where: > > - dio_new_bio() limits bio vector size artifically to > 1024 sectors / page size because bio_get_nr_vecs() > is used q->max_sectors to size the new bio; and > - dio_bio_add_page() limits the total bio size to 1024 > sectors because bio_add_page() now uses q->max_sectors > to limit the size of the bio. > > Therefore, we can't build direct I/Os larger than 1024 sectors even > if the hardware supports large I/Os. This is a regression as before > this mod we were able to issue direct I/Os limited by either the > maximum number of vectors in an bio or the hardware limits. > > The patch below (against 2.6.16) allows direct I/O to build bios as > large as the underlying hardware will allow. > > Signed-off-by: Dave Chinner > --- > bio.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > Index: 2.6.x-xfs-new/fs/bio.c > =================================================================== > --- 2.6.x-xfs-new.orig/fs/bio.c 2006-02-06 11:57:50.000000000 +1100 > +++ 2.6.x-xfs-new/fs/bio.c 2006-04-24 15:46:16.849484424 +1000 > @@ -304,7 +304,7 @@ int bio_get_nr_vecs(struct block_device > request_queue_t *q = bdev_get_queue(bdev); > int nr_pages; > > - nr_pages = ((q->max_sectors << 9) + PAGE_SIZE - 1) >> PAGE_SHIFT; > + nr_pages = ((q->max_hw_sectors << 9) + PAGE_SIZE - 1) >> PAGE_SHIFT; > if (nr_pages > q->max_phys_segments) > nr_pages = q->max_phys_segments; > if (nr_pages > q->max_hw_segments) > @@ -446,7 +446,7 @@ int bio_add_page(struct bio *bio, struct > unsigned int offset) > { > struct request_queue *q = bdev_get_queue(bio->bi_bdev); > - return __bio_add_page(q, bio, page, len, offset, q->max_sectors); > + return __bio_add_page(q, bio, page, len, offset, q->max_hw_sectors); > } > > struct bio_map_data { Clearly correct, I'll make sure this gets merged right away. -- Jens Axboe