block: add blk_rq_aligned helper function

This adds blk_rq_aligned helper function to see if alignment and
padding requirement is satisfied for DMA transfer. This also converts
blk_rq_map_kern and __blk_rq_map_user to use the helper function.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 9 insertions, 10 deletions

diff --git a/block/blk-map.c b/block/blk-map.c
index dad6a2907835..572140cda5ff 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -45,7 +45,6 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
                              unsigned int len, gfp_t gfp_mask)
 {
         unsigned long uaddr;
-        unsigned int alignment;
         struct bio *bio, *orig_bio;
         int reading, ret;
 
@@ -56,8 +55,7 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
          * direct dma. else, set up kernel bounce buffers
          */
         uaddr = (unsigned long) ubuf;
-        alignment = queue_dma_alignment(q) | q->dma_pad_mask;
-        if (!(uaddr & alignment) && !(len & alignment) && !map_data)
+        if (blk_rq_aligned(q, ubuf, len) && !map_data)
                 bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);
         else
                 bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask);
@@ -274,8 +272,6 @@ EXPORT_SYMBOL(blk_rq_unmap_user);
 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;
@@ -285,11 +281,7 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
         if (!len || !kbuf)
                 return -EINVAL;
 
-        kaddr = (unsigned long)kbuf;
-        alignment = queue_dma_alignment(q) | q->dma_pad_mask;
-        do_copy = ((kaddr & alignment) || (len & alignment) ||
-                   object_is_on_stack(kbuf));
-
+        do_copy = !blk_rq_aligned(q, kbuf, len) || object_is_on_stack(kbuf);
         if (do_copy)
                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
         else
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 358ac423ed2f..9c2549260427 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -899,6 +899,13 @@ static inline int queue_dma_alignment(struct request_queue *q)
         return q ? q->dma_alignment : 511;
 }
 
+static inline int blk_rq_aligned(struct request_queue *q, void *addr,
+                                 unsigned int len)
+{
+        unsigned int alignment = queue_dma_alignment(q) | q->dma_pad_mask;
+        return !((unsigned long)addr & alignment) && !(len & alignment);
+}
+
 /* assumes size > 256 */
 static inline unsigned int blksize_bits(unsigned int size)
 {