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Date:   Wed, 27 Feb 2019 09:13:14 +0800
From:   "Huang\, Ying" <>
To:     Daniel Jordan <>
Cc:     Andrea Arcangeli <>,
        Andrew Morton <>,
        <>, <>,
        Hugh Dickins <>,
        "Paul E . McKenney" <>,
        Minchan Kim <>,
        Johannes Weiner <>,
        "Tim Chen" <>,
        Mel Gorman <>,
        Jérôme Glisse <>,
        Michal Hocko <>,
        David Rientjes <>,
        Rik van Riel <>, Jan Kara <>,
        Dave Jiang <>,
        Aaron Lu <>,
        Andrea Parri <>
Subject: Re: [PATCH -mm -V8] mm, swap: fix race between swapoff and some swap operations

Daniel Jordan <> writes:

> On Tue, Feb 26, 2019 at 02:49:05PM +0800, Huang, Ying wrote:
>> Do you have time to take a look at this patch?
> Hi Ying, is this handling all places where swapoff might cause a task to read
> invalid data?  For example, why don't other reads of swap_map (for example
> swp_swapcount, page_swapcount, swap_entry_free) need to be synchronized like
> this?

I have checked these places.  They are safe because there are some locks
(like page lock, page table lock, etc.) held to prevent swapoff.  I
found another place in the kernel that is unsafe: the mincore.  I have a
patch for that and will post it (in fact again) after this one is

Best Regards,
Huang, Ying

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