From 11c3e689f1c3a73e3af7b0ea767b1b0626da8033 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Mon, 31 Dec 2007 16:37:00 -0600 Subject: [SCSI] block: Introduce new blk_queue_update_dma_alignment interface The purpose of this is to allow stacked alignment settings, with the ultimate queue alignment being set to the largest alignment requirement in the stack. The reason for this is so that the SCSI mid-layer can relax the default alignment requirements (which are basically causing a lot of superfluous copying to go on in the SG_IO interface) while allowing transports, devices or HBAs to add stricter limits if they need them. Acked-by: Jens Axboe Signed-off-by: James Bottomley --- block/ll_rw_blk.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) (limited to 'block/ll_rw_blk.c') diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index 8b919940b2a..14af36c5cdb 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -759,6 +759,30 @@ void blk_queue_dma_alignment(struct request_queue *q, int mask) EXPORT_SYMBOL(blk_queue_dma_alignment); +/** + * blk_queue_update_dma_alignment - update dma length and memory alignment + * @q: the request queue for the device + * @mask: alignment mask + * + * description: + * update required memory and length aligment for direct dma transactions. + * If the requested alignment is larger than the current alignment, then + * the current queue alignment is updated to the new value, otherwise it + * is left alone. The design of this is to allow multiple objects + * (driver, device, transport etc) to set their respective + * alignments without having them interfere. + * + **/ +void blk_queue_update_dma_alignment(struct request_queue *q, int mask) +{ + BUG_ON(mask > PAGE_SIZE); + + if (mask > q->dma_alignment) + q->dma_alignment = mask; +} + +EXPORT_SYMBOL(blk_queue_update_dma_alignment); + /** * blk_queue_find_tag - find a request by its tag and queue * @q: The request queue for the device -- cgit v1.2.3-70-g09d2