linux-kernel - Re: [PATCH 3/3] mm: memory-failure: make action

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Message-ID: <20221023235633.GC4024629@hori.linux.bs1.fc.nec.co.jp>
Date:   Sun, 23 Oct 2022 23:56:33 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] mm: memory-failure: make action_result() return int

On Fri, Oct 21, 2022 at 04:46:11PM +0800, Kefeng Wang wrote:
> Check mf_result in action_result(), only return 0 when MF_RECOVERED,
> or return -EBUSY, which will simplify code a bit.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>

Thanks for the cleanup, Kefeng.
I basically agree with the change. I have one comment below ...

> ---
>  mm/memory-failure.c | 42 ++++++++++++++++--------------------------
>  1 file changed, 16 insertions(+), 26 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index ca0199d0f79d..3f469e2da047 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1182,14 +1182,16 @@ static struct page_state error_states[] = {
>   * "Dirty/Clean" indication is not 100% accurate due to the possibility of
>   * setting PG_dirty outside page lock. See also comment above set_page_dirty().
>   */
> -static void action_result(unsigned long pfn, enum mf_action_page_type type,
> -			  enum mf_result result)
> +static int action_result(unsigned long pfn, enum mf_action_page_type type,
> +			 enum mf_result result)
>  {
>  	trace_memory_failure_event(pfn, type, result);
>  
>  	num_poisoned_pages_inc();
>  	pr_err("%#lx: recovery action for %s: %s\n",
>  		pfn, action_page_types[type], action_name[result]);
> +
> +	return result == MF_RECOVERED ? 0 : -EBUSY;

I think that MF_DELAYED may be considered as success (returning 0), then
page_action() can be cleaned up a little more (like below?)

    static int page_action(struct page_state *ps, struct page *p,
                            unsigned long pfn)
    {
            int result;
    
            /* page p should be unlocked after returning from ps->action().  */
            result = ps->action(ps, p);
    
            /* Could do more checks here if page looks ok */
            /*
             * Could adjust zone counters here to correct for the missing page.
             */
    
            return action_result(pfn, ps->type, result);
    }

Existing direct callers (I mean action_result() called from other than
page_action()) are never called with result==MF_DELAYED, so this change
should not affect them.

Does it make sense for you?

Thanks,
Naoya Horiguchi