ext2: cache NULL when both default_acl and acl are NULL

default_acl and acl of newly created inode will be initiated as
ACL_NOT_CACHED in vfs function inode_init_always() and later will be
updated by calling xxx_init_acl() in specific filesystems.  However,
when default_acl and acl are NULL, then they keep the value of
ACL_NOT_CACHED. This patch changes the code to cache NULL for acl /
default_acl in this case to save unnecessary ACL lookup in future.
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/acl.c

@@ -256,11 +256,15 @@ ext2_init_acl(struct inode *inode, struct inode *dir)
 	if (default_acl) {
 		error = __ext2_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
 		posix_acl_release(default_acl);
+	} else {
+		inode->i_default_acl = NULL;
 	}
 	if (acl) {
 		if (!error)
 			error = __ext2_set_acl(inode, acl, ACL_TYPE_ACCESS);
 		posix_acl_release(acl);
+	} else {
+		inode->i_acl = NULL;
 	}
 	return error;
 }