diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e3126c0..1ad7d10 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5855,14 +5855,15 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	 */
 	down_read(&inode->i_alloc_sem);
 	size = i_size_read(inode);
+	lock_page(page);
 	if (page->mapping != mapping || size <= page_offset(page)
 	    || !PageUptodate(page)) {
+		unlock_page(page);
 		/* page got truncated from under us? */
 		goto out_unlock;
 	}
 	ret = 0;
 
-	lock_page(page);
 	wait_on_page_writeback(page);
 	if (PageMappedToDisk(page)) {
 		up_read(&inode->i_alloc_sem);