ocfs2: implement i_op->permission

Implement .permission() in ocfs2_file_iops, ocfs2_special_file_iops and
ocfs2_dir_iops.

This helps us avoid some multi-node races with mode change and vfs
operations.

Signed-off-by: Tiger Yang <tiger.yang@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index b64ef7c6..8786b3c 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -945,6 +945,28 @@
 	return err;
 }
 
+int ocfs2_permission(struct inode *inode, int mask, struct nameidata *nd)
+{
+	int ret;
+
+	mlog_entry_void();
+
+	ret = ocfs2_meta_lock(inode, NULL, 0);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	ret = generic_permission(inode, mask, NULL);
+	if (ret)
+		mlog_errno(ret);
+
+	ocfs2_meta_unlock(inode, 0);
+out:
+	mlog_exit(ret);
+	return ret;
+}
+
 static int ocfs2_write_remove_suid(struct inode *inode)
 {
 	int ret;
@@ -1329,11 +1351,13 @@
 struct inode_operations ocfs2_file_iops = {
 	.setattr	= ocfs2_setattr,
 	.getattr	= ocfs2_getattr,
+	.permission	= ocfs2_permission,
 };
 
 struct inode_operations ocfs2_special_file_iops = {
 	.setattr	= ocfs2_setattr,
 	.getattr	= ocfs2_getattr,
+	.permission	= ocfs2_permission,
 };
 
 const struct file_operations ocfs2_fops = {