block: simplify bio_map_kern

Just open code the trivial mapping from a kernel virtual address to
a bio instead of going through the complex user address mapping
machinery.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/bio.c b/block/bio.c
index 471d7382c7d17b7f8929b827b217650a93d67e84..54da51ed43de19ef2efa598233b56467e775053f 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1563,9 +1563,8 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
 {
        struct bio_vec *bvec;
        const int read = bio_data_dir(bio) == READ;
-       struct bio_map_data *bmd = bio->bi_private;
+       char *p = bio->bi_private;
        int i;
-       char *p = bmd->sgvecs[0].iov_base;
 
        bio_for_each_segment_all(bvec, bio, i) {
                char *addr = page_address(bvec->bv_page);
@@ -1577,7 +1576,6 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
                p += bvec->bv_len;
        }
 
-       kfree(bmd);
        bio_put(bio);
 }
 
@@ -1595,28 +1593,58 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
 struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
                          gfp_t gfp_mask, int reading)
 {
-       struct bio *bio;
+       unsigned long kaddr = (unsigned long)data;
+       unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+       unsigned long start = kaddr >> PAGE_SHIFT;
        struct bio_vec *bvec;
-       int i;
+       struct bio *bio;
+       void *p = data;
+       int nr_pages = 0, i;
 
-       bio = bio_copy_user(q, NULL, (unsigned long)data, len, 1, gfp_mask);
-       if (IS_ERR(bio))
-               return bio;
+       /*
+        * Overflow, abort
+        */
+       if (end < start)
+               return ERR_PTR(-EINVAL);
 
-       if (!reading) {
-               void *p = data;
+       nr_pages = end - start;
+       bio = bio_kmalloc(gfp_mask, nr_pages);
+       if (!bio)
+               return ERR_PTR(-ENOMEM);
 
-               bio_for_each_segment_all(bvec, bio, i) {
-                       char *addr = page_address(bvec->bv_page);
+       while (len) {
+               struct page *page;
+               unsigned int bytes = PAGE_SIZE;
 
-                       memcpy(addr, p, bvec->bv_len);
-                       p += bvec->bv_len;
-               }
+               if (bytes > len)
+                       bytes = len;
+
+               page = alloc_page(q->bounce_gfp | gfp_mask);
+               if (!page)
+                       goto cleanup;
+
+               if (!reading)
+                       memcpy(page_address(page), p, bytes);
+
+               if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
+                       break;
+
+               len -= bytes;
+               p += bytes;
        }
 
-       bio->bi_end_io = bio_copy_kern_endio;
+       if (!reading)
+               bio->bi_rw |= REQ_WRITE;
 
+       bio->bi_private = data;
+       bio->bi_end_io = bio_copy_kern_endio;
        return bio;
+
+cleanup:
+       bio_for_each_segment_all(bvec, bio, i)
+               __free_page(bvec->bv_page);
+       bio_put(bio);
+       return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL(bio_copy_kern);