linux-kernel - Re: [PATCHi v2] mm: put_and_wait_on_page

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Date:   Mon, 26 Nov 2018 20:53:45 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>, Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        David Herrmann <dh.herrmann@...il.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Christoph Lameter <cl@...ux.com>,
        Nick Piggin <npiggin@...il.com>, pifang@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHi v2] mm: put_and_wait_on_page_locked() while page is
 migrated

On Mon 26-11-18 11:27:07, Hugh Dickins wrote:
[...]
> @@ -1049,25 +1056,44 @@ static void wake_up_page(struct page *page, int bit)
>  	wake_up_page_bit(page, bit);
>  }
>  
> +/*
> + * A choice of three behaviors for wait_on_page_bit_common():
> + */
> +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.
> +			 */
> +};

I like this. It makes to semantic much more clear.

Thanks!
-- 
Michal Hocko
SUSE Labs