misc/59683: t_nullmnt should check vfs.generic.fstypes for skip condition

[campbell+netbsd%mumble.net@localhost]

>Number:         59683
>Category:       misc
>Synopsis:       t_nullmnt should check vfs.generic.fstypes for skip condition
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    misc-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 02 13:10:00 +0000 2025
>Originator:     Taylor R Campbell
>Release:        current, 11, 10
>Organization:
Test NullBSD Skipper LLC
>Environment:
>Description:

	This change adapted t_nullmnt to skip rather than fail on
	kernels without nullfs support:

changeset:   1192671:a7894420e1cd
branch:      trunk
user:        martin <martin%NetBSD.org@localhost>
date:        Mon Jun 02 18:50:40 2025 +0000
files:       tests/lib/libc/kevent_nullmnt/t_nullmnt.sh
description:
Skip the tests when the nullmount fails (kernel w/o file-system NULLFS)


diff -r 17520c1b785c -r a7894420e1cd tests/lib/libc/kevent_nullmnt/t_nullmnt.sh
--- a/tests/lib/libc/kevent_nullmnt/t_nullmnt.sh	Mon Jun 02 18:08:15 2025 +0000
+++ b/tests/lib/libc/kevent_nullmnt/t_nullmnt.sh	Mon Jun 02 18:50:40 2025 +0000
@@ -11,7 +11,8 @@ nullmnt_common()
 {    
 	mkdir ${curdir}/lower_dir
 	mkdir ${curdir}/upper_dir
-	mount -t null ${curdir}/lower_dir ${curdir}/upper_dir
+	mount -t null ${curdir}/lower_dir ${curdir}/upper_dir || \
+		atf_skip "nullfs not supported"
 	rm -f ${curdir}/lower_dir/afile
 	touch ${curdir}/lower_dir/afile
 

	Rather than check whether `mount -t null' works at all as the
	condition for skipping, it should check whether `null' appears
	in sysctl vfs.generic.fstypes -- and it should fail if `mount
	-t null' fails in that case.


>How-To-Repeat:

	code inspection


>Fix:

	case " "$(sysctl vfs.generic.fstypes)" " in
	*" null "*)
		;;
	*)	atf_skip "nullfs not supported on this kernel"
		;;
	esac