1 files changed, 22 insertions, 14 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 711cee103602..062299acbccd 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -788,6 +788,7 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
         int i, ret;
         int nr_pages = 0;
         unsigned int len = 0;
+        unsigned int offset = map_data ? map_data->offset & ~PAGE_MASK : 0;
 
         for (i = 0; i < iov_count; i++) {
                 unsigned long uaddr;
@@ -814,35 +815,42 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
         bio->bi_rw |= (!write_to_vm << BIO_RW);
 
         ret = 0;
-        i = 0;
+
+        if (map_data) {
+                nr_pages = 1 << map_data->page_order;
+                i = map_data->offset / PAGE_SIZE;
+        }
         while (len) {
-                unsigned int bytes;
+                unsigned int bytes = PAGE_SIZE;
 
-                if (map_data)
-                        bytes = 1U << (PAGE_SHIFT + map_data->page_order);
-                else
-                        bytes = PAGE_SIZE;
+                bytes -= offset;
 
                 if (bytes > len)
                         bytes = len;
 
                 if (map_data) {
-                        if (i == map_data->nr_entries) {
+                        if (i == map_data->nr_entries * nr_pages) {
                                 ret = -ENOMEM;
                                 break;
                         }
-                        page = map_data->pages[i++];
-                } else
+
+                        page = map_data->pages[i / nr_pages];
+                        page += (i % nr_pages);
+
+                        i++;
+                } else {
                         page = alloc_page(q->bounce_gfp | gfp_mask);
-                if (!page) {
-                        ret = -ENOMEM;
-                        break;
+                        if (!page) {
+                                ret = -ENOMEM;
+                                break;
+                        }
                 }
 
-                if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
+                if (bio_add_pc_page(q, bio, page, bytes, offset) < bytes)
                         break;
 
                 len -= bytes;
+                offset = 0;
         }
 
         if (ret)
@@ -851,7 +859,7 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
         /*
          * success
          */
-        if (!write_to_vm) {
+        if (!write_to_vm && (!map_data || !map_data->null_mapped)) {
                 ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 0);
                 if (ret)
                         goto cleanup;