selftests/mm: hugetlb_madv_vs_map: Avoid test skipping by querying hugepage size at runtime

Currently, the size used in mmap() is statically defined, leading to
skipping of the test on a hugepage size other than 2 MB, since munmap()
won't free the hugepage for a size greater than 2 MB. Hence, query the
size at runtime.

Also, there is no reason why a hugepage allocation should fail, since we
are using a simple mmap() using MAP_HUGETLB; hence, instead of skipping
the test, make it fail.
 
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
 tools/testing/selftests/mm/hugetlb_madv_vs_map.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

On 5/9/24 2:54 PM, Dev Jain wrote:
> Currently, the size used in mmap() is statically defined, leading to
> skipping of the test on a hugepage size other than 2 MB, since munmap()
> won't free the hugepage for a size greater than 2 MB. Hence, query the
> size at runtime.
> 
> Also, there is no reason why a hugepage allocation should fail, since we
> are using a simple mmap() using MAP_HUGETLB; hence, instead of skipping
> the test, make it fail.
>  
> Signed-off-by: Dev Jain <dev.jain@arm.com>
LGTM
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>

> ---
>  tools/testing/selftests/mm/hugetlb_madv_vs_map.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/hugetlb_madv_vs_map.c b/tools/testing/selftests/mm/hugetlb_madv_vs_map.c
> index d01e8d4901d0..8f122a0f0828 100644
> --- a/tools/testing/selftests/mm/hugetlb_madv_vs_map.c
> +++ b/tools/testing/selftests/mm/hugetlb_madv_vs_map.c
> @@ -27,9 +27,9 @@
>  #include "vm_util.h"
>  #include "../kselftest.h"
>  
> -#define MMAP_SIZE (1 << 21)
>  #define INLOOP_ITER 100
>  
> +size_t mmap_size;
>  char *huge_ptr;
>  
>  /* Touch the memory while it is being madvised() */
> @@ -44,7 +44,7 @@ void *touch(void *unused)
>  void *madv(void *unused)
>  {
>  	for (int i = 0; i < INLOOP_ITER; i++)
> -		madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED);
> +		madvise(huge_ptr, mmap_size, MADV_DONTNEED);
>  
>  	return NULL;
>  }
> @@ -59,7 +59,7 @@ void *map_extra(void *unused)
>  	void *ptr;
>  
>  	for (int i = 0; i < INLOOP_ITER; i++) {
> -		ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,
> +		ptr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
>  			   MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
>  			   -1, 0);
>  
> @@ -93,14 +93,16 @@ int main(void)
>  			       free_hugepages);
>  	}
>  
> +	mmap_size = default_huge_page_size();
> +
>  	while (max--) {
> -		huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,
> +		huge_ptr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
>  				MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
>  				-1, 0);
>  
>  		if ((unsigned long)huge_ptr == -1) {
> -			ksft_exit_skip("Failed to allocated huge page\n");
> -			return KSFT_SKIP;
> +			ksft_test_result_fail("Failed to allocate huge page\n");
> +			return KSFT_FAIL;
>  		}
>  
>  		pthread_create(&thread1, NULL, madv, NULL);
> @@ -117,7 +119,7 @@ int main(void)
>  		}
>  
>  		/* Unmap and restart */
> -		munmap(huge_ptr, MMAP_SIZE);
> +		munmap(huge_ptr, mmap_size);
>  	}
>  
>  	return KSFT_PASS;

Am 09.05.24 um 11:54 schrieb Dev Jain:
> Currently, the size used in mmap() is statically defined, leading to
> skipping of the test on a hugepage size other than 2 MB, since munmap()
> won't free the hugepage for a size greater than 2 MB. Hence, query the
> size at runtime.
> 
> Also, there is no reason why a hugepage allocation should fail, since we
> are using a simple mmap() using MAP_HUGETLB; hence, instead of skipping
> the test, make it fail.
>   
> Signed-off-by: Dev Jain <dev.jain@arm.com>
> ---


Likely it would make sense to rewrite that test to try with all available 
hugetlb sizes (like cow.c does).

Acked-by: David Hildenbrand <david@redhat.com>