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References: <20210113024241.179113-1-ying.huang@intel.com>
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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 12 Jan 2021 18:47:16 -0800
Message-ID: <CAHk-=whn5kVxEitkC0AyzvWRyxbF91rMrO9ZG6JHBNYLckpDDw@mail.gmail.com>
Subject: Re: [PATCH] mm: Free unused swap cache page in write protection fault handler
To:     Huang Ying <ying.huang@intel.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Xu <peterx@redhat.com>, Hugh Dickins <hughd@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@surriel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Tim Chen <tim.c.chen@intel.com>
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On Tue, Jan 12, 2021 at 6:43 PM Huang Ying <ying.huang@intel.com> wrote:
>
> So in this patch, at the end of wp_page_copy(), the old unused swap
> cache page will be tried to be freed.

I'd much rather free it later when needed, rather than when you're in
a COW section.

            Linus