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Subject: Re: [PATCH 2/2] mm/page_alloc: use a single function to free page
To:     Aaron Lu <aaron.lu@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        =?UTF-8?Q?Pawe=c5=82_Staszewski?= <pstaszewski@itcare.pl>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        Tariq Toukan <tariqt@mellanox.com>,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        Yoel Caspersen <yoel@kviknet.dk>,
        Mel Gorman <mgorman@techsingularity.net>,
        Saeed Mahameed <saeedm@mellanox.com>,
        Michal Hocko <mhocko@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Dave Hansen <dave.hansen@linux.intel.com>
References: <20181105085820.6341-1-aaron.lu@intel.com>
 <20181105085820.6341-2-aaron.lu@intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
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Message-ID: <a91592dd-83eb-ab9d-7f59-637928f964f8@intel.com>
Date:   Mon, 5 Nov 2018 08:39:23 -0800
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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.