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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 26 Nov 2018 11:30:07 -0800
Message-ID: <CAHk-=wix+0_ED+78Q43Sk+hoObO+Q1DoSOqq_TLnH2=wcNHx2A@mail.gmail.com>
Subject: Re: [PATCHi v2] mm: put_and_wait_on_page_locked() while page is migrated
To:     Hugh Dickins <hughd@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>, bhe@redhat.com,
        Michal Hocko <mhocko@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andrea Arcangeli <aarcange@redhat.com>, david@redhat.com,
        mgorman@techsingularity.net,
        David Herrmann <dh.herrmann@gmail.com>,
        Tim Chen <tim.c.chen@linux.intel.com>, kan.liang@intel.com,
        Andi Kleen <ak@linux.intel.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Christoph Lameter <cl@linux.com>,
        Nick Piggin <npiggin@gmail.com>, pifang@redhat.com,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        linux-mm@kvack.org
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On Mon, Nov 26, 2018 at 11:27 AM Hugh Dickins <hughd@google.com> wrote:
>
> +enum behavior {
> +       EXCLUSIVE,      /* Hold ref to page and take the bit when woken, like
> +                        * __lock_page() waiting on then setting PG_locked.
> +                        */
> +       SHARED,         /* Hold ref to page and check the bit when woken, like
> +                        * wait_on_page_writeback() waiting on PG_writeback.
> +                        */
> +       DROP,           /* Drop ref to page before wait, no check when woken,
> +                        * like put_and_wait_on_page_locked() on PG_locked.
> +                        */
> +};

Ack, thanks.

                Linus