Re: [PATCH v4 07/10] powerpc/mm: Use generic_hugetlb_get_unmapped_area()

Nicholas Piggin
2021-12-09T10:02:12Z

Excerpts from Christophe Leroy's message of December 9, 2021 3:18 am:
> Use the generic version of arch_hugetlb_get_unmapped_area()
> which is now available at all time.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/include/asm/book3s/64/hugetlb.h | 4 --
> arch/powerpc/mm/book3s64/radix_hugetlbpage.c | 55 --------------------
> arch/powerpc/mm/hugetlbpage.c | 4 +-
> 3 files changed, 1 insertion(+), 62 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h b/arch/powerpc/include/asm/book3s/64/hugetlb.h
> index 12e150e615b7..b37a28f62cf6 100644
> --- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
> +++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
> @@ -8,10 +8,6 @@
> */
> void radix__flush_hugetlb_page(struct vm_area_struct *vma, unsigned long vmaddr);
> void radix__local_flush_hugetlb_page(struct vm_area_struct *vma, unsigned long vmaddr);
> -extern unsigned long
> -radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> - unsigned long len, unsigned long pgoff,
> - unsigned long flags);
>
> extern void radix__huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
> unsigned long addr, pte_t *ptep,
> diff --git a/arch/powerpc/mm/book3s64/radix_hugetlbpage.c b/arch/powerpc/mm/book3s64/radix_hugetlbpage.c
> index 23d3e08911d3..d2fb776febb4 100644
> --- a/arch/powerpc/mm/book3s64/radix_hugetlbpage.c
> +++ b/arch/powerpc/mm/book3s64/radix_hugetlbpage.c
> @@ -41,61 +41,6 @@ void radix__flush_hugetlb_tlb_range(struct vm_area_struct *vma, unsigned long st
> radix__flush_tlb_range_psize(vma->vm_mm, start, end, psize);
> }
>
> -/*
> - * A vairant of hugetlb_get_unmapped_area doing topdown search
> - * FIXME!! should we do as x86 does or non hugetlb area does ?
> - * ie, use topdown or not based on mmap_is_legacy check ?
> - */
> -unsigned long
> -radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> - unsigned long len, unsigned long pgoff,
> - unsigned long flags)
> -{
> - struct mm_struct *mm = current->mm;
> - struct vm_area_struct *vma;
> - struct hstate *h = hstate_file(file);
> - int fixed = (flags & MAP_FIXED);
> - unsigned long high_limit;
> - struct vm_unmapped_area_info info;
> -
> - high_limit = DEFAULT_MAP_WINDOW;
> - if (addr >= high_limit || (fixed && (addr + len > high_limit)))
> - high_limit = TASK_SIZE;

I wonder if generic hugetlb_get_unmapped_area needs to have the
arch_get_mmap_end() added.

arm64 has arch_get_mmap_end() and !HAVE_ARCH_HUGETLB_UNMAPPED_AREA so
it looks like it has broken large address hint logic for hugetlbfs
mappings? x86-64 defines their own and does the same hinting for
normal and hugetlbfs mmap.

If we had that and defied arch_get_mmap_end(), then this patch should
work.

Thanks,
Nick