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    SubjectRe: [PATCH] mm/shmem: Inline shmem_is_huge() for disabled transparent hugepages
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    On 10.04.24 18:51, Peter Xu wrote:
    > On Wed, Apr 10, 2024 at 06:40:55PM +0200, David Hildenbrand wrote:
    >> On 10.04.24 18:33, Peter Xu wrote:
    >>> On Wed, Apr 10, 2024 at 06:12:34PM +0200, David Hildenbrand wrote:
    >>>> On 10.04.24 18:07, Sumanth Korikkar wrote:
    >>>>> On Wed, Apr 10, 2024 at 05:51:28PM +0200, David Hildenbrand wrote:
    >>>>>> 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?
    >>>>>
    >>>>> It's not yet upstream.
    >>>>>>
    >>>>>>>
    >>>>>>> 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@redhat.com>
    >>>>>> 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.
    >>>>>
    >>>>> Not related to this commit. I tried on master branch.
    >>>>
    >>>> Thanks! Can you try with Peters patch? (ccing Peter)
    >>>>
    >>>> If I am not wrong, that should also resolve the issue you are seeing.
    >>>
    >>> David,
    >>>
    >>> Do you mean this one?
    >>>
    >>> https://lore.kernel.org/all/20240403013249.1418299-4-peterx@redhat.com/
    >>>
    >>
    >> No, I meant:
    >>
    >> https://lore.kernel.org/all/20240327152332.950956-4-peterx@redhat.com/
    >>
    >> which removes the "#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })" that we
    >> seem to trigger here.
    >>
    >>
    >> ... but it's been a long day, so maybe I'm all wrong :)
    >
    > Ah.. So I thought it was one step further. :)
    >
    > Then that shouldn't be the case; it didn't remove it but defined properly
    > with HPAGE_PMD_SHIFT:
    >
    > +#define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
    >
    > Now we even have that properly defined for HUGETLB_PAGE, while prior to
    > that we should hit this issue easier (even with !THP+HUGETLB_PAGE).

    Ah, now I spot

    #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })

    :) sorry for the noise!

    To the original patch here

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

    --
    Cheers,

    David / dhildenb


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