NFS: fsync() must exit with an error if page writeback failed

We need to ensure that if the call to filemap_write_and_wait_range()
fails, then we report that error back to the application.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 75d6d0a..6a7fcab 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -287,10 +287,12 @@
 	struct inode *inode = file->f_path.dentry->d_inode;
 
 	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (ret != 0)
+		goto out;
 	mutex_lock(&inode->i_mutex);
 	ret = nfs_file_fsync_commit(file, start, end, datasync);
 	mutex_unlock(&inode->i_mutex);
-
+out:
 	return ret;
 }