linux-kernel - Re: [PATCH -mm] mm, swap: Fix false error message in __swp

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Date:   Wed, 25 Oct 2017 10:32:52 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     "Huang\, Ying" <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "Michal Hocko" <mhocko@...e.com>, <stable@...r.kernel.org>,
        Christian Kujau <lists@...dbynature.de>
Subject: Re: [PATCH -mm] mm, swap: Fix false error message in __swp_swapcount()

Minchan Kim <minchan@...nel.org> writes:

> On Tue, Oct 24, 2017 at 10:47:00AM +0800, Huang, Ying wrote:
>> From: Ying Huang <ying.huang@...el.com>
>> 
>> __swp_swapcount() is used in __read_swap_cache_async().  Where the
>> invalid swap entry (offset > max) may be supplied during swap
>> readahead.  But __swp_swapcount() will print error message for these
>> expected invalid swap entry as below, which will make the users
>> confusing.
>> 
>>   swap_info_get: Bad swap offset entry 0200f8a7
>> 
>> So the swap entry checking code in __swp_swapcount() is changed to
>> avoid printing error message for it.  To avoid to duplicate code with
>> __swap_duplicate(), a new helper function named
>> __swap_info_get_silence() is added and invoked in both places.
>
> It's the problem caused by readahead, not __swap_info_get which is low-end
> primitive function. Instead, please fix high-end swapin_readahead to limit
> to last valid block as handling to avoid swap header which is special case,
> too.

Yes.  You are right, will send the new version.

Best Regards,
Huang, Ying