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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>
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1 parent 657e93b commit 68154e90c9d1492d570671ae181d9a8f8530da55 @fujita fujita committed with Jens Axboe Apr 25, 2008
Showing with 112 additions and 1 deletion.
  1. +20 −1 block/blk-map.c
  2. +90 −0 fs/bio.c
  3. +2 −0 include/linux/bio.h
View
21 block/blk-map.c
@@ -255,24 +255,43 @@ 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))
return -EINVAL;
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;
View
90 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);
View
2 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);

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