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Date: Wed, 25 Oct 2017 05:17:08 +0900
From: Minchan Kim <minchan@kernel.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Tim Chen <tim.c.chen@linux.intel.com>,
        Michal Hocko <mhocko@suse.com>, stable@vger.kernel.org,
        Christian Kujau <lists@nerdbynature.de>
Subject: Re: [PATCH -mm] mm, swap: Fix false error message in
 __swp_swapcount()
Message-ID: <20171024201708.GA25022@bgram>
References: <20171024024700.23679-1-ying.huang@intel.com>
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On Tue, Oct 24, 2017 at 10:47:00AM +0800, Huang, Ying wrote:
> From: Ying Huang <ying.huang@intel.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.