vfs: no mnt_want_write_file() in vfs_{copy,clone}_file_range()

We've checked for file_out being opened for write.  This ensures that we
already have mnt_want_write() on target.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/read_write.c

@@ -1538,9 +1538,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	if (len == 0)
 		return 0;
 
-	ret = mnt_want_write_file(file_out);
-	if (ret)
-		return ret;
+	sb_start_write(inode_out->i_sb);
 
 	ret = -EOPNOTSUPP;
 	if (file_out->f_op->copy_file_range)
@@ -1559,7 +1557,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
 	inc_syscr(current);
 	inc_syscw(current);
 
-	mnt_drop_write_file(file_out);
+	sb_end_write(inode_out->i_sb);
 
 	return ret;
 }
@@ -1685,9 +1683,7 @@ int vfs_clone_file_range(struct file *file_in, loff_t pos_in,
 	if (pos_in + len > i_size_read(inode_in))
 		return -EINVAL;
 
-	ret = mnt_want_write_file(file_out);
-	if (ret)
-		return ret;
+	sb_start_write(inode_out->i_sb);
 
 	ret = file_in->f_op->clone_file_range(file_in, pos_in,
 			file_out, pos_out, len);
@@ -1696,7 +1692,7 @@ int vfs_clone_file_range(struct file *file_in, loff_t pos_in,
 		fsnotify_modify(file_out);
 	}
 
-	mnt_drop_write_file(file_out);
+	sb_end_write(inode_out->i_sb);
 	return ret;
 }
 EXPORT_SYMBOL(vfs_clone_file_range);