linux-kernel - Re: [PATCH v2] selftests: mm: fix map_hugetlb failure on 64K page size systems

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Date: Sat, 20 Jan 2024 20:39:04 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Nico Pache <npache@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-mm@...ck.org, shuah@...nel.org, donettom@...ux.vnet.ibm.com,
 Christophe Leroy <christophe.leroy@....fr>, Michael Ellerman
 <mpe@...erman.id.au>
Subject: Re: [PATCH v2] selftests: mm: fix map_hugetlb failure on 64K page
 size systems

On Fri, 19 Jan 2024 06:14:29 -0700 Nico Pache <npache@...hat.com> wrote:

> On systems with 64k page size and 512M huge page sizes, the allocation
> and test succeeds but errors out at the munmap. As the comment states,
> munmap will failure if its not HUGEPAGE aligned. This is due to the
> length of the mapping being 1/2 the size of the hugepage causing the
> munmap to not be hugepage aligned. Fix this by making the mapping length
> the full hugepage if the hugepage is larger than the length of the
> mapping.

Is

Fixes: fa7b9a805c79 ("tools/selftest/vm: allow choosing mem size and page size in map_hugetlb")

a suitable Fixes: target for this?

> --- a/tools/testing/selftests/mm/map_hugetlb.c
> +++ b/tools/testing/selftests/mm/map_hugetlb.c
> @@ -15,6 +15,7 @@
>  #include <unistd.h>
>  #include <sys/mman.h>
>  #include <fcntl.h>
> +#include "vm_util.h"
>  
>  #define LENGTH (256UL*1024*1024)
>  #define PROTECTION (PROT_READ | PROT_WRITE)
> @@ -58,10 +59,16 @@ int main(int argc, char **argv)
>  {
>  	void *addr;
>  	int ret;
> +	size_t hugepage_size;
>  	size_t length = LENGTH;
>  	int flags = FLAGS;
>  	int shift = 0;
>  
> +	hugepage_size = default_huge_page_size();
> +	/* munmap with fail if the length is not page aligned */
> +	if (hugepage_size > length)
> +		length = hugepage_size;
> +
>  	if (argc > 1)
>  		length = atol(argv[1]) << 20;
>  	if (argc > 2) {
> -- 
> 2.43.0