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,
Huang Ying <huang.ying.caritas@gmail.com>,
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 -V3] mm, swap: Fix false error message in __swp_swapcount()
Date: Thu, 2 Nov 2017 14:50:19 +0900 [thread overview]
Message-ID: <20171102055019.GA26929@bbox> (raw)
In-Reply-To: <20171102054225.22897-1-ying.huang@intel.com>
On Thu, Nov 02, 2017 at 01:42:25PM +0800, Huang, Ying wrote:
> From: Huang Ying <huang.ying.caritas@gmail.com>
>
> When a page fault occurs for a swap entry, the physical swap readahead
> (not the VMA base swap readahead) may readahead several swap entries
> after the fault swap entry. The readahead algorithm calculates some
> of the swap entries to readahead via increasing the offset of the
> fault swap entry without checking whether they are beyond the end of
> the swap device and it relys on the __swp_swapcount() and
> swapcache_prepare() to check it. Although __swp_swapcount() checks
> for the swap entry passed in, it will complain with the error message
> as follow for the expected invalid swap entry. This may make the end
> users confused.
>
> swap_info_get: Bad swap offset entry 0200f8a7
>
> To fix the false error message, the swap entry checking is added in
> swapin_readahead() to avoid to pass the out-of-bound swap entries and
> the swap entry reserved for the swap header to __swp_swapcount() and
> swapcache_prepare().
>
> Cc: Tim Chen <tim.c.chen@linux.intel.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: <stable@vger.kernel.org> # 4.11-4.13
> Fixes: e8c26ab60598 ("mm/swap: skip readahead for unreferenced swap slots")
> Reported-by: Christian Kujau <lists@nerdbynature.de>
> Suggested-by: Minchan Kim <minchan@kernel.org>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Minchan Kim <minchan@kernel.org>
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prev parent reply other threads:[~2017-11-02 5:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-02 5:42 [PATCH -mm -V3] mm, swap: Fix false error message in __swp_swapcount() Huang, Ying
2017-11-02 5:50 ` Minchan Kim [this message]
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