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 (file)
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -255,10 +255,18 @@ EXPORT_SYMBOL(blk_rq_unmap_user);
  * @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 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
        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;

diff --git a/fs/bio.c b/fs/bio.c
index 6e0b6f6..799f86d 100644 (file)
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -937,6 +937,95 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
        return ERR_PTR(-EINVAL);
 }
 
+static void bio_copy_kern_endio(struct bio *bio, int err)
+{
+       struct bio_vec *bvec;
+       const int read = bio_data_dir(bio) == READ;
+       char *p = bio->bi_private;
+       int i;
+
+       __bio_for_each_segment(bvec, bio, i, 0) {
+               char *addr = page_address(bvec->bv_page);
+
+               if (read && !err)
+                       memcpy(p, addr, bvec->bv_len);
+
+               __free_page(bvec->bv_page);
+               p += bvec->bv_len;
+       }
+
+       bio_put(bio);
+}
+
+/**
+ *     bio_copy_kern   -       copy kernel address into bio
+ *     @q: the struct request_queue for the bio
+ *     @data: pointer to buffer to copy
+ *     @len: length in bytes
+ *     @gfp_mask: allocation flags for bio and page allocation
+ *
+ *     copy the kernel address into a bio suitable for io to a block
+ *     device. Returns an error pointer in case of error.
+ */
+struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
+                         gfp_t gfp_mask, int reading)
+{
+       unsigned long kaddr = (unsigned long)data;
+       unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+       unsigned long start = kaddr >> PAGE_SHIFT;
+       const int nr_pages = end - start;
+       struct bio *bio;
+       struct bio_vec *bvec;
+       int i, ret;
+
+       bio = bio_alloc(gfp_mask, nr_pages);
+       if (!bio)
+               return ERR_PTR(-ENOMEM);
+
+       while (len) {
+               struct page *page;
+               unsigned int bytes = PAGE_SIZE;
+
+               if (bytes > len)
+                       bytes = len;
+
+               page = alloc_page(q->bounce_gfp | gfp_mask);
+               if (!page) {
+                       ret = -ENOMEM;
+                       goto cleanup;
+               }
+
+               if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes) {
+                       ret = -EINVAL;
+                       goto cleanup;
+               }
+
+               len -= bytes;
+       }
+
+       if (!reading) {
+               void *p = data;
+
+               bio_for_each_segment(bvec, bio, i) {
+                       char *addr = page_address(bvec->bv_page);
+
+                       memcpy(addr, p, bvec->bv_len);
+                       p += bvec->bv_len;
+               }
+       }
+
+       bio->bi_private = data;
+       bio->bi_end_io = bio_copy_kern_endio;
+       return bio;
+cleanup:
+       bio_for_each_segment(bvec, bio, i)
+               __free_page(bvec->bv_page);
+
+       bio_put(bio);
+
+       return ERR_PTR(ret);
+}
+
 /*
  * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
  * for performing direct-IO in BIOs.
@@ -1273,6 +1362,7 @@ EXPORT_SYMBOL(bio_get_nr_vecs);
 EXPORT_SYMBOL(bio_map_user);
 EXPORT_SYMBOL(bio_unmap_user);
 EXPORT_SYMBOL(bio_map_kern);
+EXPORT_SYMBOL(bio_copy_kern);
 EXPORT_SYMBOL(bio_pair_release);
 EXPORT_SYMBOL(bio_split);
 EXPORT_SYMBOL(bio_split_pool);

diff --git a/include/linux/bio.h b/include/linux/bio.h
index d259690..61c15ea 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -324,6 +324,8 @@ extern struct bio *bio_map_user_iov(struct request_queue *,
 extern void bio_unmap_user(struct bio *);
 extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
                                gfp_t);
+extern struct bio *bio_copy_kern(struct request_queue *, void *, unsigned int,
+                                gfp_t, int);
 extern void bio_set_pages_dirty(struct bio *bio);
 extern void bio_check_pages_dirty(struct bio *bio);
 extern struct bio *bio_copy_user(struct request_queue *, unsigned long, unsigned int, int);