linux-kernel - Re: [PATCH 1/3] swap: Use __try_to_reclaim_swap() in free_swap_and

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Date:   Mon, 27 Aug 2018 15:44:37 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Huang Ying <ying.huang@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shaohua Li <shli@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH 1/3] swap: Use __try_to_reclaim_swap() in
 free_swap_and_cache()

On Mon, 27 Aug 2018 15:55:33 +0800 Huang Ying <ying.huang@...el.com> wrote:

> The code path to reclaim the swap entry in free_swap_and_cache() is
> almost same as that of __try_to_reclaim_swap().  The largest
> difference is just coding style.  So the support to the additional
> requirement of free_swap_and_cache() is added into
> __try_to_reclaim_swap().  free_swap_and_cache() is changed to call
> __try_to_reclaim_swap(), and delete the duplicated code.  This will
> improve code readability and reduce the potential bugs.
> 
> There are 2 functionality differences between __try_to_reclaim_swap()
> and swap entry reclaim code of free_swap_and_cache().
> 
> - free_swap_and_cache() only reclaims the swap entry if the page is
>   unmapped or swap is getting full.  The support has been added into
>   __try_to_reclaim_swap().
> 
> - try_to_free_swap() (called by __try_to_reclaim_swap()) checks
>   pm_suspended_storage(), while free_swap_and_cache() not.  I think
>   this is OK.  Because the page and the swap entry can be reclaimed
>   later eventually.

hm.  Having functions take `mode' arguments which specify their actions
in this manner isn't popular (Linus ;)) but I guess the end result is
somewhat better.