linux-kernel - Re: [PATCH v4 7/8] mm: Use static initialisers for immutable fields of 'struct vm

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Date:   Wed, 20 Jan 2021 10:21:33 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Jan Kara <jack@...e.cz>, Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Hugh Dickins <hughd@...gle.com>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH v4 7/8] mm: Use static initialisers for immutable fields
 of 'struct vm_fault'

On Wed, Jan 20, 2021 at 9:36 AM Will Deacon <will@...nel.org> wrote:
>
> In preparation for const-ifying the anonymous struct field of
> 'struct vm_fault', ensure that it is initialised using static
> initialisers.

FWIW these are known as "designated initializers", ie.

struct foo my_foo = {
  .bar = 42,
};

https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Will Deacon <will@...nel.org>
> ---
>  mm/shmem.c    |  6 +++---
>  mm/swapfile.c | 11 ++++++-----
>  2 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 7c6b6d8f6c39..1b254fbfdf52 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1520,11 +1520,11 @@ static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
>  {
>         struct vm_area_struct pvma;
>         struct page *page;
> -       struct vm_fault vmf;
> +       struct vm_fault vmf = {
> +               .vma = &pvma,
> +       };
>
>         shmem_pseudo_vma_init(&pvma, info, index);
> -       vmf.vma = &pvma;
> -       vmf.address = 0;
>         page = swap_cluster_readahead(swap, gfp, &vmf);
>         shmem_pseudo_vma_destroy(&pvma);
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 9fffc5af29d1..2b570a566276 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1951,8 +1951,6 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
>         si = swap_info[type];
>         pte = pte_offset_map(pmd, addr);
>         do {
> -               struct vm_fault vmf;
> -
>                 if (!is_swap_pte(*pte))
>                         continue;
>
> @@ -1968,9 +1966,12 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
>                 swap_map = &si->swap_map[offset];
>                 page = lookup_swap_cache(entry, vma, addr);
>                 if (!page) {
> -                       vmf.vma = vma;
> -                       vmf.address = addr;
> -                       vmf.pmd = pmd;
> +                       struct vm_fault vmf = {
> +                               .vma = vma,
> +                               .address = addr,
> +                               .pmd = pmd,
> +                       };
> +
>                         page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
>                                                 &vmf);
>                 }
> --
> 2.30.0.284.gd98b1dd5eaa7-goog
>


--
Thanks,
~Nick Desaulniers