From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750825AbWDXGOO (ORCPT ); Mon, 24 Apr 2006 02:14:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750832AbWDXGOO (ORCPT ); Mon, 24 Apr 2006 02:14:14 -0400 Received: from omx2-ext.sgi.com ([192.48.171.19]:23968 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S1750825AbWDXGON (ORCPT ); Mon, 24 Apr 2006 02:14:13 -0400 Date: Mon, 24 Apr 2006 16:14:03 +1000 From: David Chinner To: linux-kernel@vger.kernel.org Subject: [PATCH] Direct I/O bio size regression Message-ID: <20060424061403.GF611708@melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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 {