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

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Date:   Tue, 27 Nov 2018 10:10:51 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Hugh Dickins <hughd@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>, Michal Hocko <mhocko@...e.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 Tue, Nov 27, 2018 at 12:58:48PM +0200, Mike Rapoport wrote:
> > diff --git a/mm/filemap.c b/mm/filemap.c
> > index 81adec8ee02c..575e16c037ca 100644
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -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.
> > +			 */
> > +};
> 
> Can we please make it:
> 
> /**
>  * enum behavior - a choice of three behaviors for wait_on_page_bit_common()
>  */

The enum isn't used outside mm/filemap.c, so I'm not entirely sure that
including kernel-doc for it is a good idea.