Subject: Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure

From: Peter Zijlstra <[email-masked]>
Date: Wed, 30 Aug 2017 07:58:00 +0200

On Wed, Aug 30, 2017 at 10:33:50AM +0530, Anshuman Khandual wrote:
> diff --git a/mm/filemap.c b/mm/filemap.c
> index a497024..08f3042 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1181,6 +1181,18 @@ int __lock_page_killable(struct page *__page)
>  int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
>                          unsigned int flags)
>  {
> +       if (flags & FAULT_FLAG_SPECULATIVE) {
> +               if (flags & FAULT_FLAG_KILLABLE) {
> +                       int ret;
> +
> +                       ret = __lock_page_killable(page);
> +                       if (ret)
> +                               return 0;
> +               } else
> +                       __lock_page(page);
> +               return 1;
> +       }
> +
>         if (flags & FAULT_FLAG_ALLOW_RETRY) {
>                 /*
>                  * CAUTION! In this case, mmap_sem is not released

Yeah, that looks right.

> @@ -4012,17 +4010,7 @@ int handle_speculative_fault(struct mm_struct *mm, unsigned long address,
>                 goto unlock;
>         }
> 
> +       if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
>                 trace_spf_vma_notsup(_RET_IP_, vma, address);
>                 goto unlock;
>         }

As riel pointed out on IRC slightly later, private file maps also need
->anon_vma and those actually have ->vm_ops IIRC so the condition needs
to be slightly more complicated.