Btrfs: fix btrfs page_mkwrite to return locked page

This closes a whole where the page may be written before
the page_mkwrite caller has a chance to dirty it

(thanks to Nick Piggin)

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 233fe6f26120..c846482e7985 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4552,11 +4552,14 @@ again:
         }
         ClearPageChecked(page);
         set_page_dirty(page);
+        SetPageUptodate(page);
 
         BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;
         unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
 
 out_unlock:
+        if (!ret)
+                return VM_FAULT_LOCKED;
         unlock_page(page);
 out:
         return ret;