Re: [PATCH v3 2/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when migration

Andrew Morton
2022-05-10T23:28:47Z

On Tue, 10 May 2022 16:17:39 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> > +
> > +static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
> > + unsigned long addr, pte_t *ptep)
> > +{
> > + return ptep_get(ptep);
> > +}
> > +
> > +static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
> > + pte_t *ptep, pte_t pte)
> > +{
> > +}
> > #endif /* CONFIG_HUGETLB_PAGE */
> >
>
> This blows up nommu (arm allnoconfig):
>
> In file included from fs/io_uring.c:71:
> ./include/linux/hugetlb.h: In function 'huge_ptep_clear_flush':
> ./include/linux/hugetlb.h:1100:16: error: implicit declaration of function 'ptep_get' [-Werror=implicit-function-declaration]
> 1100 | return ptep_get(ptep);
> | ^~~~~~~~
>
>
> huge_ptep_clear_flush() is only used in CONFIG_NOMMU=n files, so I simply
> zapped this change.
>

Well that wasn't a great success. Doing this instead. It's pretty
nasty - something nicer would be nicer please.

--- a/include/linux/hugetlb.h~mm-rmap-fix-cont-pte-pmd-size-hugetlb-issue-when-migration-fix
+++ a/include/linux/hugetlb.h
@@ -1094,6 +1094,7 @@ static inline void set_huge_swap_pte_at(
{
}

+#ifdef CONFIG_MMU
static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{
@@ -1104,6 +1105,7 @@ static inline void set_huge_pte_at(struc
pte_t *ptep, pte_t pte)
{
}
+#endif
#endif /* CONFIG_HUGETLB_PAGE */

static inline spinlock_t *huge_pte_lock(struct hstate *h,
_