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

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

[Nico Pache]

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.

Signed-off-by: Nico Pache <npache@redhat.com>
---
 tools/testing/selftests/mm/map_hugetlb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/testing/selftests/mm/map_hugetlb.c b/tools/testing/selftests/mm/map_hugetlb.c
index 193281560b61..86e8f2048a40 100644
--- 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

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

[Andrew Morton]

On Fri, 19 Jan 2024 06:14:29 -0700 Nico Pache <npache@redhat.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

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

[Nico Pache]

Hi Andrew,

No, I think it's always been broken-- I don't think the test was
written with 512M huge page sizes in mind.

-- Nico

On Sat, Jan 20, 2024 at 9:39 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Fri, 19 Jan 2024 06:14:29 -0700 Nico Pache <npache@redhat.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
>