linux-kernel - Re: [PATCH 2/2] mm/page_alloc: use a single function to free page

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Date:   Mon, 5 Nov 2018 08:39:23 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Aaron Lu <aaron.lu@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Paweł Staszewski <pstaszewski@...are.pl>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Yoel Caspersen <yoel@...knet.dk>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 2/2] mm/page_alloc: use a single function to free page

On 11/5/18 12:58 AM, Aaron Lu wrote:
> We have multiple places of freeing a page, most of them doing similar
> things and a common function can be used to reduce code duplicate.
> 
> It also avoids bug fixed in one function and left in another.

Haha, should have read the next patch. :)

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 91a9a6af41a2..2b330296e92a 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4425,9 +4425,17 @@ unsigned long get_zeroed_page(gfp_t gfp_mask)
>  }
>  EXPORT_SYMBOL(get_zeroed_page);
>  
> -void __free_pages(struct page *page, unsigned int order)
> +/*
> + * Free a page by reducing its ref count by @nr.
> + * If its refcount reaches 0, then according to its order:
> + * order0: send to PCP;
> + * high order: directly send to Buddy.
> + */

FWIW, I'm not a fan of comments on the function like this.  Please just
comment the *code* that's doing what you describe.  It's easier to read
and less likely to diverge from the code.

The rest of the patch looks great, though.