1 files changed, 1 insertions, 1 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 51466dcd44e0..5fa450452f9b 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -764,7 +764,7 @@ static int prepare_pages(struct btrfs_root *root, struct file *file,
         }
         if (start_pos < inode->i_size) {
                 u64 last_pos;
-                last_pos = (index + num_pages) << PAGE_CACHE_SHIFT;
+                last_pos = ((u64)index + num_pages) << PAGE_CACHE_SHIFT;
                 lock_extent(&BTRFS_I(inode)->io_tree,
                             start_pos, last_pos - 1, GFP_NOFS);
                 clear_extent_bits(&BTRFS_I(inode)->io_tree, start_pos,