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Tue, 27 Nov 2018 13:09:03 -0800 (PST) Date: Tue, 27 Nov 2018 13:08:50 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Mike Rapoport cc: Matthew Wilcox , Hugh Dickins , Linus Torvalds , Andrew Morton , Baoquan He , Michal Hocko , Vlastimil Babka , Andrea Arcangeli , David Hildenbrand , Mel Gorman , David Herrmann , Tim Chen , Kan Liang , Andi Kleen , Davidlohr Bueso , Peter Zijlstra , Christoph Lameter , Nick Piggin , pifang@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHi v2] mm: put_and_wait_on_page_locked() while page is migrated In-Reply-To: <20181127105848.GD16502@rapoport-lnx> Message-ID: References: <20181127105848.GD16502@rapoport-lnx> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 Nov 2018, Mike Rapoport wrote: > On Mon, Nov 26, 2018 at 11:27:07AM -0800, Hugh Dickins wrote: > > > > +/* > > + * 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() > */ > enum behavior { > /** > * @EXCLUSIVE: Hold ref to page and take the bit when woken, > * like __lock_page() waiting on then setting %PG_locked. > */ > EXCLUSIVE, > /** > * @SHARED: Hold ref to page and check the bit when woken, > * like wait_on_page_writeback() waiting on %PG_writeback. > */ > SHARED, > /** > * @DROP: Drop ref to page before wait, no check when woken, > * like put_and_wait_on_page_locked() on %PG_locked. > */ > DROP, > }; I'm with Matthew, I'd prefer not: the first looks a more readable, less cluttered comment to me than the second: this is just an arg to an internal helper in mm/filemap.c, itself not kernel-doc'ed. But the comment is not there for me: if consensus is that the second is preferable, then sure, we can change it over. Hugh