linux-kernel - Re: [PATCH 01/11] mm: page_vma_mapped

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Message-ID: <3489192.qTgHbfadoh@nvdebian>
Date:   Thu, 10 Jun 2021 18:12:40 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Hugh Dickins <hughd@...gle.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Ralph Campbell" <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Peter Xu <peterx@...hat.com>, Will Deacon <will@...nel.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/11] mm: page_vma_mapped_walk(): use page for pvmw->page

Thanks for this, I've read through page_vma_mapped_walk() a few too many times
recently and it annoyed me enough to start writing some patches to clean it up,
but happy to see this instead.

I confirmed pvmw->page isn't modified here or in map/check_pte(pvmw), so the
patch looks good to me:

Reviewed-by: Alistair Popple <apopple@...dia.com>

On Thursday, 10 June 2021 4:34:40 PM AEST Hugh Dickins wrote:
> page_vma_mapped_walk() cleanup: sometimes the local copy of pvwm->page was
> used, sometimes pvmw->page itself: use the local copy "page" throughout.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Cc: <stable@...r.kernel.org>
> ---
>  mm/page_vma_mapped.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index e37bd43904af..a6dbf714ca15 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -156,7 +156,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>         if (pvmw->pte)
>                 goto next_pte;
> 
> -       if (unlikely(PageHuge(pvmw->page))) {
> +       if (unlikely(PageHuge(page))) {
>                 /* when pud is not present, pte will be NULL */
>                 pvmw->pte = huge_pte_offset(mm, pvmw->address, page_size(page));
>                 if (!pvmw->pte)
> @@ -217,8 +217,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>                  * cannot return prematurely, while zap_huge_pmd() has
>                  * cleared *pmd but not decremented compound_mapcount().
>                  */
> -               if ((pvmw->flags & PVMW_SYNC) &&
> -                   PageTransCompound(pvmw->page)) {
> +               if ((pvmw->flags & PVMW_SYNC) && PageTransCompound(page)) {
>                         spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
> 
>                         spin_unlock(ptl);
> @@ -234,9 +233,9 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>                         return true;
>  next_pte:
>                 /* Seek to next pte only makes sense for THP */
> -               if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page))
> +               if (!PageTransHuge(page) || PageHuge(page))
>                         return not_found(pvmw);
> -               end = vma_address_end(pvmw->page, pvmw->vma);
> +               end = vma_address_end(page, pvmw->vma);
>                 do {
>                         pvmw->address += PAGE_SIZE;
>                         if (pvmw->address >= end)
> --
> 2.26.2
>