Define a new API for mapping array of pages into a request.
Internally the bio is created using the
rq_map_data + null_mapped + NULL_buffer mode of
bio_copy_user(). The bio is only referenced once
and there is no unmap function to call.
TODO:
out of the 7 users of blk_rq_map_user + rq_map_data, 6 of them
are null_mapped + NULL_buffer and could be converted to this
API.
Signed-off-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
---
block/blk-map.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/blkdev.h | 3 ++
2 files changed, 57 insertions(+), 0 deletions(-)
diff --git a/block/blk-map.c b/block/blk-map.c
index ada399e..60a7a0b 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -325,3 +325,57 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
return 0;
}
EXPORT_SYMBOL(blk_rq_map_kern);
+
+/**
+ * blk_rq_map_pages - map pages array to a request, for REQ_TYPE_BLOCK_PC usage
+ * @q: request queue where request should be inserted
+ * @rq: request to fill
+ * @pages: an array of struct page pointers to map
+ * @nr_pages: count of valid pages at @pages
+ * @offset: Offset into first page to start from (Must be blk_rq_aligned())
+ * @len: length of user data to map
+ * @gfp_mask: memory allocation flags
+ *
+ * Description:
+ * Data will be mapped directly if possible. Otherwise a bounce
+ * buffer is used. Can be called multiple times to append multiple
+ * page arrays. No need to call an unmap function, and bio is only
+ * referenced once. (Pages are of zero order)
+ */
+int blk_rq_map_pages(struct request_queue *q, struct request *rq,
+ struct page **pages, unsigned nr_pages,
+ unsigned long offset, unsigned len, gfp_t gfp_mask)
+{
+ struct bio *bio;
+ int reading, ret;
+ struct rq_map_data map_data = {
+ .pages = pages,
+ .nr_entries = nr_pages,
+ .offset = offset,
+ .null_mapped = 1,
+ .page_order = 0,
+ };
+
+ reading = rq_data_dir(rq) == READ;
+
+ /* The name is confusing, but bio_copy_user+map_data+NULL_buffer
+ * Actually just adds the pages to the bio, no copy is performed.
+ */
+ bio = bio_copy_user(q, &map_data, 0, len, reading, gfp_mask);
+
+ if (IS_ERR(bio))
+ return PTR_ERR(bio);
+
+ bio->bi_flags |= (1 << BIO_NULL_MAPPED);
+
+ /* We might still need to bounce if memory mask does not match */
+ blk_queue_bounce(q, &bio);
+
+ ret = blk_rq_append_bio(q, rq, bio);
+ if (likely(!ret))
+ return 0;
+
+ bio_put(bio);
+ return ret;
+}
+EXPORT_SYMBOL(blk_rq_map_pages);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 22dcdde..81b681c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -784,6 +784,9 @@ extern int blk_rq_map_user(struct request_queue *, struct request *,
extern int blk_rq_unmap_user(struct bio *);
extern int blk_rq_map_kern(struct request_queue *, struct request *, void *,
unsigned int, gfp_t);
+extern int blk_rq_map_pages(struct request_queue *, struct request *,
+ struct page **, unsigned, unsigned long offset,
+ unsigned , gfp_t);
extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
struct rq_map_data *, struct sg_iovec *, int,
unsigned int, gfp_t);
--
1.6.2.1
--
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