Re: [PATCH v6 1/6] selftests/mm/guard-regions: skip collapse test when thp not enabled

[Lorenzo Stoakes (Oracle)]

On Tue, Mar 24, 2026 at 09:33:11AM +0800, Chunyu Hu wrote:
> When thp is not available, just skip the collape tests to avoid the false
> negative.
>
> Without the change, run with a thp disabled kernel:
>   ./run_vmtests.sh -t madv_guard -n 1
>   <snip/>
>   #  RUN           guard_regions.anon.collapse ...
>   # guard-regions.c:2217:collapse:Expected madvise(ptr, size, MADV_NOHUGEPAGE) (-1) == 0 (0)
>   # collapse: Test terminated by assertion
>   #          FAIL  guard_regions.anon.collapse
>   not ok 2 guard_regions.anon.collapse
>   <snip/>
>   #  RUN           guard_regions.shmem.collapse ...
>   # guard-regions.c:2217:collapse:Expected madvise(ptr, size, MADV_NOHUGEPAGE) (-1) == 0 (0)
>   # collapse: Test terminated by assertion
>   #          FAIL  guard_regions.shmem.collapse
>   not ok 32 guard_regions.shmem.collapse
>   <snip/>
>   #  RUN           guard_regions.file.collapse ...
>   # guard-regions.c:2217:collapse:Expected madvise(ptr, size, MADV_NOHUGEPAGE) (-1) == 0 (0)
>   # collapse: Test terminated by assertion
>   #          FAIL  guard_regions.file.collapse
>   not ok 62 guard_regions.file.collapse
>   <snip/>
>   # FAILED: 87 / 90 tests passed.
>   # 17 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
>   # Totals: pass:70 fail:3 xfail:0 xpass:0 skip:17 error:0
>
> With this change, run with thp disabled kernel:
>   ./run_vmtests.sh -t madv_guard -n 1
>   <snip/>
>   #  RUN           guard_regions.anon.collapse ...
>   #      SKIP      Transparent Hugepages not available
>   #            OK  guard_regions.anon.collapse
>   ok 2 guard_regions.anon.collapse # SKIP Transparent Hugepages not available
>   <snip/>
>   #  RUN           guard_regions.file.collapse ...
>   #      SKIP      Transparent Hugepages not available
>   #            OK  guard_regions.file.collapse
>   ok 62 guard_regions.file.collapse # SKIP Transparent Hugepages not available
>   <snip/>
>   #  RUN           guard_regions.shmem.collapse ...
>   #      SKIP      Transparent Hugepages not available
>   #            OK  guard_regions.shmem.collapse
>   ok 32 guard_regions.shmem.collapse # SKIP Transparent Hugepages not available
>   <snip/>
>   # PASSED: 90 / 90 tests passed.
>   # 20 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
>   # Totals: pass:70 fail:0 xfail:0 xpass:0 skip:20 error:0
>
> Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> CC: Li Wang <liwang@xxxxxxxxxx>
> Signed-off-by: Chunyu Hu <chuhu@xxxxxxxxxx>

Pretty sure I reviewed this already (but hey I forget to propagate tags myself
sometimes so meh :P), anyway:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>

Cheers, Lorenzo

> ---
> Changes in v5:
>   - updated reviewed-by and acked-by
> Changes in v4:
>   - use thp_available instead of thp_is_enabled() as when thp is set to
>     never, madvise(MADV_COLLAPSE) will still succeed by design. So a
>     failure in madvise(MADV_COLLAPSE) on guard region will verify guard
>     region denies it. This is suggested from AI.
>   - removed the 'Reviewed-by' and 'Acked-by' as the code changes. Sorry for
>     that but it seems the changes is a little huge? (1 out of 2 lines)..
> Changes in v3:
>   - commit message: update the log snippet with where the fail happens and
>     add the '-n1' to the command.
>   - fix the 'false positive' to 'false negative'
>   - add reviwed by from Mike
> Changes in v2:
>   - add reviewed by from Zi and Lorenzo
>   - add acked-by from David
> ---
>  tools/testing/selftests/mm/guard-regions.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
> index dbd21d66d383..48e8b1539be3 100644
> --- a/tools/testing/selftests/mm/guard-regions.c
> +++ b/tools/testing/selftests/mm/guard-regions.c
> @@ -21,6 +21,7 @@
>  #include <sys/uio.h>
>  #include <unistd.h>
>  #include "vm_util.h"
> +#include "thp_settings.h"
>
>  #include "../pidfd/pidfd.h"
>
> @@ -2195,6 +2196,9 @@ TEST_F(guard_regions, collapse)
>  	char *ptr;
>  	int i;
>
> +	if (!thp_available())
> +		SKIP(return, "Transparent Hugepages not available\n");
> +
>  	/* Need file to be correct size for tests for non-anon. */
>  	if (variant->backing != ANON_BACKED)
>  		ASSERT_EQ(ftruncate(self->fd, size), 0);
> --
> 2.53.0
>