Messages in this thread Patch in this message | | | Date | Mon, 24 Apr 2006 16:14:03 +1000 | From | David Chinner <> | Subject | [PATCH] Direct I/O bio size regression |
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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 <dgc@sgi.com> --- 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 { - 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/
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