linux-kernel - Re: [PATCH v2] mm/hugepages: fix "orig

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Message-ID: <CAFqt6zZr8ZCM6_7QDzDEf=5gH=+EkaumXk86X35dGTdn_SLvvA@mail.gmail.com>
Date:   Mon, 4 Mar 2019 17:32:23 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/hugepages: fix "orig_pud" set but not used

On Sat, Mar 2, 2019 at 3:50 AM Qian Cai <cai@....pw> wrote:
>
> The commit a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent
> hugepages") introduced pudp_huge_get_and_clear_full() but no one uses
> its return code. In order to not diverge from
> pmdp_huge_get_and_clear_full(), just change zap_huge_pud() to not assign
> the return value from pudp_huge_get_and_clear_full().
>
> mm/huge_memory.c: In function 'zap_huge_pud':
> mm/huge_memory.c:1982:8: warning: variable 'orig_pud' set but not used
> [-Wunused-but-set-variable]
>   pud_t orig_pud;
>         ^~~~~~~~
>

4th argument passed to pudp_huge_get_and_clear_full() is not used.
Is it fine to remove *int full * in  pudp_huge_get_and_clear_full() if
there is no plan to use it in future ?

This is applicable to below functions as well -
pmdp_huge_get_and_clear_full()
ptep_get_and_clear_full()
pte_clear_not_present_full()




> Signed-off-by: Qian Cai <cai@....pw>
> ---
>
> v2: keep returning a code from pudp_huge_get_and_clear_full() for possible
>     future uses.
>
>  mm/huge_memory.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index faf357eaf0ce..9f57a1173e6a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1979,7 +1979,6 @@ spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
>  int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
>                  pud_t *pud, unsigned long addr)
>  {
> -       pud_t orig_pud;
>         spinlock_t *ptl;
>
>         ptl = __pud_trans_huge_lock(pud, vma);
> @@ -1991,8 +1990,7 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
>          * pgtable_trans_huge_withdraw after finishing pudp related
>          * operations.
>          */
> -       orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
> -                       tlb->fullmm);
> +       pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
>         tlb_remove_pud_tlb_entry(tlb, pud, addr);
>         if (vma_is_dax(vma)) {
>                 spin_unlock(ptl);
> --
> 2.17.2 (Apple Git-113)
>