linux-kernel - Re: [PATCH 1/1] mm/migrate: fix list corruption in migration of non-LRU movable pages

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Date:   Tue, 10 Sep 2019 21:31:20 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     sunqiuyang <sunqiuyang@...wei.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/1] mm/migrate: fix list corruption in migration of
 non-LRU movable pages

On Tue 10-09-19 12:23:04, Minchan Kim wrote:
> On Tue, Sep 03, 2019 at 04:27:46PM +0800, sunqiuyang wrote:
> > From: Qiuyang Sun <sunqiuyang@...wei.com>
> > 
> > Currently, after a page is migrated, it
> > 1) has its PG_isolated flag cleared in move_to_new_page(), and
> > 2) is deleted from its LRU list (cc->migratepages) in unmap_and_move().
> > However, between steps 1) and 2), the page could be isolated by another
> > thread in isolate_movable_page(), and added to another LRU list, leading
> > to list_del corruption later.
> 
> Once non-LRU page is migrated out successfully, driver should clear
> the movable flag in the page. Look at reset_page in zs_page_migrate.
> So, other thread couldn't isolate the page during the window.
> 
> If I miss something, let me know it.

Please have a look at http://lkml.kernel.org/r/157FC541501A9C4C862B2F16FFE316DC190C5990@dggeml512-mbx.china.huawei.com
-- 
Michal Hocko
SUSE Labs