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>

fs/ocfs2/file.c

@@ -945,6 +945,28 @@ int ocfs2_getattr(struct vfsmount *mnt,
 	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 @@ static ssize_t ocfs2_file_aio_read(struct kiocb *iocb,
 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 = {

fs/ocfs2/file.h

@@ -48,6 +48,8 @@ int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
 int ocfs2_setattr(struct dentry *dentry, struct iattr *attr);
 int ocfs2_getattr(struct vfsmount *mnt, struct dentry *dentry,
 		  struct kstat *stat);
+int ocfs2_permission(struct inode *inode, int mask,
+		     struct nameidata *nd);
 
 int ocfs2_set_inode_size(handle_t *handle,
 			 struct inode *inode,

fs/ocfs2/namei.c

@@ -2311,4 +2311,5 @@ struct inode_operations ocfs2_dir_iops = {
 	.rename		= ocfs2_rename,
 	.setattr	= ocfs2_setattr,
 	.getattr	= ocfs2_getattr,
+	.permission	= ocfs2_permission,
 };