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Shutemov" To: Matthew Wilcox Cc: linux-mm@kvack.org, Matthew Wilcox , Martin Schwidefsky , linux-kernel@vger.kernel.org, Fengguang Wu , linux-api@vger.kernel.org Subject: Re: [PATCH v4 2/4] mm: Split page_type out from _map_count Message-ID: <20180302081806.aokjrb27hxqki7at@node.shutemov.name> References: <20180301211523.21104-1-willy@infradead.org> <20180301211523.21104-3-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180301211523.21104-3-willy@infradead.org> User-Agent: NeoMutt/20180223 Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Thu, Mar 01, 2018 at 01:15:21PM -0800, Matthew Wilcox wrote: > From: Matthew Wilcox > > We're already using a union of many fields here, so stop abusing the > _map_count and make page_type its own field. That implies renaming some s/_map_count/_mapcount/ and in subject. > of the machinery that creates PageBuddy, PageBalloon and PageKmemcg; > bring back the PG_buddy, PG_balloon and PG_kmemcg names. > > As suggested by Kirill, make page_type a bitmask. Because it starts out > life as -1 (thanks to sharing the storage with _map_count), setting a > page flag means clearing the appropriate bit. This gives us space for > probably twenty or so extra bits (depending how paranoid we want to be > about _mapcount underflow). > > Signed-off-by: Matthew Wilcox Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov