[RFC PATCH 4/6] selftests: fix build errors on alpine linux

[Hajime Tazaki]

On Fri, 14 Aug 2026 21:39:33 +0900,
Lorenzo Stoakes (ARM) wrote:
> 
> On Thu, Aug 13, 2026 at 03:33:59PM +0900, Hajime Tazaki wrote:
> > Some nommu architectures only work on Alpine Linux, which doesn't use
> > glibc for the standard library.  It uses musl-libc and is implemented in
> > a different way as glibc, resulting build failures.
> >
> > This commit fixes this issue by adding missing definitions. The fixes
> > are now only covered to TARGETS=mm which was tested for the moment;
> > future contributions are needed to fully build/execute tests on nommu
> > platforms.
> >
> > Cc: Shuah Khan <shuah at kernel.org>
> > Cc: Andrew Morton <akpm at linux-foundation.org>
> > Cc: David Hildenbrand <david at kernel.org>
> > Cc: Lorenzo Stoakes <ljs at kernel.org>
> > Cc: "Liam R. Howlett" <liam at infradead.org>
> > Cc: Vlastimil Babka <vbabka at kernel.org>
> > Cc: Mike Rapoport <rppt at kernel.org>
> > Cc: Suren Baghdasaryan <surenb at google.com>
> > Cc: Michal Hocko <mhocko at suse.com>
> > Cc: linux-kselftest at vger.kernel.org
> > Cc: linux-mm at kvack.org
> > Cc: linux-um at lists.infradead.org
> > Signed-off-by: Hajime Tazaki <thehajime at gmail.com>
> 
> I mean vaguely looks un-invasive which is the test here.
> 
> Couple comments below.
(snip)
> > diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
> > index f02cc8a2e4ae..2cc819006424 100644
> > --- a/tools/testing/selftests/lib.mk
> > +++ b/tools/testing/selftests/lib.mk
> > @@ -197,7 +197,7 @@ clean: $(if $(TEST_GEN_MODS_DIR),clean_mods_dir)
> >  	$(CLEAN)
> >
> >  # Build with _GNU_SOURCE by default
> 
> You probably want to update this comment.

indeed, will update this part (may even not needed to modify this).

> > -CFLAGS += -D_GNU_SOURCE=
> > +CFLAGS += -D_GNU_SOURCE= -D_LARGEFILE64_SOURCE

(snip)
> > diff --git a/tools/testing/selftests/mm/hugetlb_dio.c b/tools/testing/selftests/mm/hugetlb_dio.c
> > index fb4600570e13..aee6be530ccb 100644
> > --- a/tools/testing/selftests/mm/hugetlb_dio.c
> > +++ b/tools/testing/selftests/mm/hugetlb_dio.c
> > @@ -22,12 +22,9 @@
> >  #include "kselftest.h"
> >  #include "hugepage_settings.h"
> >
> > -#ifndef STATX_DIOALIGN
> > -#define STATX_DIOALIGN		0x00002000U
> > -#endif
> > -
> >  static int get_dio_alignment(int fd)
> >  {
> > +#ifdef STATX_DIOALIGN
> >  	struct statx stx;
> >  	int ret;
> >
> > @@ -43,6 +40,9 @@ static int get_dio_alignment(int fd)
> >  		return 1;
> >
> >  	return stx.stx_dio_offset_align;
> > +#else
> > +	return -1;
> > +#endif
> 
> Probably better to declare different functions to make this less hideous.

I see your point.  will look for the other way.

-- Hajime