From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 14 Dec 2018 12:03:11 -0800 From: Matthew Wilcox To: Dave Hansen Cc: Dan Williams , John Hubbard , david , =?iso-8859-1?B?Suly9G1l?= Glisse , Jan Kara , John Hubbard , Andrew Morton , Linux MM , tom@talpey.com, Al Viro , benve@cisco.com, Christoph Hellwig , Christopher Lameter , "Dalessandro, Dennis" , Doug Ledford , Jason Gunthorpe , Michal Hocko , Mike Marciniszyn , rcampbell@nvidia.com, Linux Kernel Mailing List , linux-fsdevel Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions Message-ID: <20181214200311.GH10600@bombadil.infradead.org> References: <20181212150319.GA3432@redhat.com> <20181212214641.GB29416@dastard> <20181212215931.GG5037@redhat.com> <20181213005119.GD29416@dastard> <05a68829-6e6d-b766-11b4-99e1ba4bc87b@nvidia.com> <01cf4e0c-b2d6-225a-3ee9-ef0f7e53684d@nvidia.com> <20181214194843.GG10600@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: On Fri, Dec 14, 2018 at 11:53:31AM -0800, Dave Hansen wrote: > On 12/14/18 11:48 AM, Matthew Wilcox wrote: > > I think we can do better than a proxy object with bit 0 set. I'd go > > for allocating something like this: > > > > struct dynamic_page { > > struct page; > > unsigned long vaddr; > > unsigned long pfn; > > ... > > }; > > > > and use a bit in struct page to indicate that this is a dynamic page. > > That might be fun. We'd just need a fast/static and slow/dynamic path > in page_to_pfn()/pfn_to_page(). We'd also need some kind of auxiliary > pfn-to-page structure since we could not fit that^ structure in vmemmap[]. Yes; working on the pfn-to-page structure right now as it happens ... in the meantime, an XArray for it probably wouldn't be _too_ bad.