linux-kernel - Re: [PATCH -next] mm/huge_memory.c: remove unused variable 'count'

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Message-ID: <CAHbLzkonsd9f=48+cxKOJamNb9e8qpvWJCYDGFB_wNTdET2zmQ@mail.gmail.com>
Date:   Fri, 14 May 2021 11:48:48 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Pu Lehui <pulehui@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] mm/huge_memory.c: remove unused variable 'count'

On Thu, May 13, 2021 at 11:59 PM Pu Lehui <pulehui@...wei.com> wrote:
>
> mm/huge_memory.c:2663:6: warning:
>  variable ‘count’ set but not used [-Wunused-but-set-variable]
>   2663 |  int count, mapcount, extra_pins, ret;
>        |      ^~~~~
>
> This variable is not used in function , this commit
> remove it to fix the warning.

Thanks for catching this warning. Not sure why my gcc 10 doesn't catch
this warning at all. What compiler are you using?

Andrew, the compile warning was introduced by my
mm-thp-check-total_mapcount-instead-of-page_mapcount.patch.
>
> Signed-off-by: Pu Lehui <pulehui@...wei.com>
> ---
>  mm/huge_memory.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 52ca04b905cf..a23a127302e9 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2660,7 +2660,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
>         struct deferred_split *ds_queue = get_deferred_split_queue(head);
>         struct anon_vma *anon_vma = NULL;
>         struct address_space *mapping = NULL;
> -       int count, mapcount, extra_pins, ret;
> +       int mapcount, extra_pins, ret;
>         pgoff_t end;
>
>         VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
> @@ -2737,7 +2737,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
>
>         /* Prevent deferred_split_scan() touching ->_refcount */
>         spin_lock(&ds_queue->split_queue_lock);
> -       count = page_count(head);
>         mapcount = total_mapcount(head);
>         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
>                 if (!list_empty(page_deferred_list(head))) {
> --
> 2.17.1
>
>