Re: [PATCH] mm/shmem: Inline shmem_is_huge() for disabled transparent hugepages

[David Hildenbrand]

On 10.04.24 17:26, Sumanth Korikkar wrote:
> On Wed, Apr 10, 2024 at 02:34:35PM +0200, David Hildenbrand wrote:
> > On 09.04.24 17:54, Sumanth Korikkar wrote:
> > > In order to  minimize code size (CONFIG_CC_OPTIMIZE_FOR_SIZE=y),
> > > compiler might choose to make a regular function call (out-of-line) for
> > > shmem_is_huge() instead of inlining it. When transparent hugepages are
> > > disabled (CONFIG_TRANSPARENT_HUGEPAGE=n), it can cause compilation
> > > error.
> > >
> > > mm/shmem.c: In function ‘shmem_getattr’:
> > > ./include/linux/huge_mm.h:383:27: note: in expansion of macro ‘BUILD_BUG’
> > >     383 | #define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })
> > >         |                           ^~~~~~~~~
> > > mm/shmem.c:1148:33: note: in expansion of macro ‘HPAGE_PMD_SIZE’
> > >    1148 |                 stat->blksize = HPAGE_PMD_SIZE;
> > >
> > > To prevent the possible error, always inline shmem_is_huge() when
> > > transparent hugepages are disabled.
> >
> > Do you know which commit introduced that?
> Hi David,
>
> Currently with CONFIG_CC_OPTIMIZE_FOR_SIZE=y and expirementing with
> -fPIC kernel compiler option, I could see this error on s390.

Got it. I assume on Linus' tree, not mm/unstable?

> However, default kernel compiler options doesnt end up with the above
> pattern right now.

Okay, just asking if this is related to recent HPAGE_PMD_SIZE changes:

commit c1a1e497a3d5711dbf8fa6d7432d6b83ec18c26f
Author: Peter Xu <peterx@xxxxxxxxxx>
Date:   Wed Mar 27 11:23:22 2024 -0400

    mm: make HPAGE_PXD_* macros even if !THP

Which is still in mm-unstable and not upstream.

--
Cheers,

David / dhildenb