block: add dma alignment and padding support to blk_rq_map_kern
This patch adds bio_copy_kern similar to
bio_copy_user. blk_rq_map_kern uses bio_copy_kern instead of
bio_map_kern if necessary.
bio_copy_kern uses temporary pages and the bi_end_io callback frees
these pages. bio_copy_kern saves the original kernel buffer at
bio->bi_private it doesn't use something like struct bio_map_data to
store the information about the caller.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-map.c b/block/blk-map.c
index 3c942bd..0b1af5a 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -255,10 +255,18 @@
* @kbuf: the kernel buffer
* @len: length of user data
* @gfp_mask: memory allocation flags
+ *
+ * Description:
+ * Data will be mapped directly if possible. Otherwise a bounce
+ * buffer is used.
*/
int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
unsigned int len, gfp_t gfp_mask)
{
+ unsigned long kaddr;
+ unsigned int alignment;
+ int reading = rq_data_dir(rq) == READ;
+ int do_copy = 0;
struct bio *bio;
if (len > (q->max_hw_sectors << 9))
@@ -266,13 +274,24 @@
if (!len || !kbuf)
return -EINVAL;
- bio = bio_map_kern(q, kbuf, len, gfp_mask);
+ kaddr = (unsigned long)kbuf;
+ alignment = queue_dma_alignment(q) | q->dma_pad_mask;
+ do_copy = ((kaddr & alignment) || (len & alignment));
+
+ if (do_copy)
+ bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
+ else
+ bio = bio_map_kern(q, kbuf, len, gfp_mask);
+
if (IS_ERR(bio))
return PTR_ERR(bio);
if (rq_data_dir(rq) == WRITE)
bio->bi_rw |= (1 << BIO_RW);
+ if (do_copy)
+ rq->cmd_flags |= REQ_COPY_USER;
+
blk_rq_bio_prep(q, rq, bio);
blk_queue_bounce(q, &rq->bio);
rq->buffer = rq->data = NULL;
