Messages in this thread | | | Date | Wed, 10 Apr 2024 19:03:21 +0200 | Subject | Re: [PATCH] mm/shmem: Inline shmem_is_huge() for disabled transparent hugepages | From | David Hildenbrand <> |
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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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