* Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
> When creating a hugetlb mapping, attempt PUD_SIZE alignment if the
> following conditions are met:
> - Address passed to mmap or shmat is NULL
> - The mapping is flaged as shared
> - The mapping is at least PUD_SIZE in length
> If a PUD_SIZE aligned mapping can not be created, then fall back to a
> huge page size mapping.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
> arch/x86/mm/hugetlbpage.c | 64 ++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 61 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
> index 42982b2..4f53af5 100644
> --- a/arch/x86/mm/hugetlbpage.c
> +++ b/arch/x86/mm/hugetlbpage.c
> @@ -78,14 +78,39 @@ static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
> {
> struct hstate *h = hstate_file(file);
> struct vm_unmapped_area_info info;
> + bool pud_size_align = false;
> + unsigned long ret_addr;
> +
> + /*
> + * If PMD sharing is enabled, align to PUD_SIZE to facilitate
> + * sharing. Only attempt alignment if no address was passed in,
> + * flags indicate sharing and size is big enough.
> + */
> + if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
> + !addr && flags & MAP_SHARED && len >= PUD_SIZE)
> + pud_size_align = true;
>
> info.flags = 0;
> info.length = len;
> info.low_limit = current->mm->mmap_legacy_base;
> info.high_limit = TASK_SIZE;
> - info.align_mask = PAGE_MASK & ~huge_page_mask(h);
> + if (pud_size_align)
> + info.align_mask = PAGE_MASK & (PUD_SIZE - 1);
> + else
> + info.align_mask = PAGE_MASK & ~huge_page_mask(h);
> info.align_offset = 0;
> - return vm_unmapped_area(&info);
> + ret_addr = vm_unmapped_area(&info);
> +
> + /*
> + * If failed with PUD_SIZE alignment, try again with huge page
> + * size alignment.
> + */
> + if ((ret_addr & ~PAGE_MASK) && pud_size_align) {
> + info.align_mask = PAGE_MASK & ~huge_page_mask(h);
> + ret_addr = vm_unmapped_area(&info);
> + }
So AFAICS 'ret_addr' is either page aligned, or is an error code. Wouldn't it be a
lot easier to read to say:
if ((long)ret_addr > 0 && pud_size_align) {
info.align_mask = PAGE_MASK & ~huge_page_mask(h);
ret_addr = vm_unmapped_area(&info);
}
return ret_addr;
to make it clear that it's about error handling, not some alignment
requirement/restriction?
> /*
> + * If failed with PUD_SIZE alignment, try again with huge page
> + * size alignment.
> + */
> + if ((addr & ~PAGE_MASK) && pud_size_align) {
> + info.align_mask = PAGE_MASK & ~huge_page_mask(h);
> + addr = vm_unmapped_area(&info);
> + }
Ditto.
> addr = vm_unmapped_area(&info);
> +
> + /*
> + * If failed again with PUD_SIZE alignment, finally try with
> + * huge page size alignment.
> + */
> + if (addr & ~PAGE_MASK) {
> + info.align_mask = PAGE_MASK & ~huge_page_mask(h);
> + addr = vm_unmapped_area(&info);
Ditto.
Thanks,
Ingo
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