1 files changed, 66 insertions, 0 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 3a1472acc361..707b9af2dd01 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -701,6 +701,71 @@ void bio_unmap_user(struct bio *bio)
         bio_put(bio);
 }
 
+static struct bio *__bio_map_kern(request_queue_t *q, void *data,
+                                  unsigned int len, unsigned int gfp_mask)
+{
+        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;
+        int offset, i;
+        struct bio *bio;
+
+        bio = bio_alloc(gfp_mask, nr_pages);
+        if (!bio)
+                return ERR_PTR(-ENOMEM);
+
+        offset = offset_in_page(kaddr);
+        for (i = 0; i < nr_pages; i++) {
+                unsigned int bytes = PAGE_SIZE - offset;
+
+                if (len <= 0)
+                        break;
+
+                if (bytes > len)
+                        bytes = len;
+
+                if (__bio_add_page(q, bio, virt_to_page(data), bytes,
+                                   offset) < bytes)
+                        break;
+
+                data += bytes;
+                len -= bytes;
+                offset = 0;
+        }
+
+        return bio;
+}
+
+/**
+ *      bio_map_kern    -       map kernel address into bio
+ *      @q: the request_queue_t for the bio
+ *      @data: pointer to buffer to map
+ *      @len: length in bytes
+ *      @gfp_mask: allocation flags for bio allocation
+ *
+ *      Map the kernel address into a bio suitable for io to a block
+ *      device. Returns an error pointer in case of error.
+ */
+struct bio *bio_map_kern(request_queue_t *q, void *data, unsigned int len,
+                         unsigned int gfp_mask)
+{
+        struct bio *bio;
+
+        bio = __bio_map_kern(q, data, len, gfp_mask);
+        if (IS_ERR(bio))
+                return bio;
+
+        if (bio->bi_size == len)
+                return bio;
+
+        /*
+         * Don't support partial mappings.
+         */
+        bio_put(bio);
+        return ERR_PTR(-EINVAL);
+}
+
 /*
  * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
  * for performing direct-IO in BIOs.
@@ -1088,6 +1153,7 @@ EXPORT_SYMBOL(bio_add_page);
 EXPORT_SYMBOL(bio_get_nr_vecs);
 EXPORT_SYMBOL(bio_map_user);
 EXPORT_SYMBOL(bio_unmap_user);
+EXPORT_SYMBOL(bio_map_kern);
 EXPORT_SYMBOL(bio_pair_release);
 EXPORT_SYMBOL(bio_split);
 EXPORT_SYMBOL(bio_split_pool);