From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 4 Jul 2003 02:46:41 +0200 From: Andrea Arcangeli Subject: Re: What to expect with the 2.6 VM Message-ID: <20030704004641.GR23578@dualathlon.random> References: <20030702231122.GI26348@holomorphy.com> <20030702233014.GW23578@dualathlon.random> <20030702235540.GK26348@holomorphy.com> <20030703113144.GY23578@dualathlon.random> <20030703114626.GP26348@holomorphy.com> <20030703125839.GZ23578@dualathlon.random> <20030703184825.GA17090@mail.jlokier.co.uk> <20030703185431.GQ26348@holomorphy.com> <20030703193328.GN23578@dualathlon.random> <20030703222113.GS26348@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030703222113.GS26348@holomorphy.com> Sender: owner-linux-mm@kvack.org Return-Path: To: William Lee Irwin III , Jamie Lokier , "Martin J. Bligh" , Mel Gorman , Linux Memory Management List , Linux Kernel Mailing List List-ID: On Thu, Jul 03, 2003 at 03:21:13PM -0700, William Lee Irwin III wrote: > On Thu, Jul 03, 2003 at 11:54:31AM -0700, William Lee Irwin III wrote: > >> I call that application #2. > > On Thu, Jul 03, 2003 at 09:33:28PM +0200, Andrea Arcangeli wrote: > > maybe I'm missing something but protections have nothing to do with > > remap_file_pages IMHO. That's all about teaching the swap code to > > reserve more bits in the swap entry and to store the protections there > > and possibly teaching the page fault not to get confused. It might > > prefer to use the populate callback too to avoid specializing the > > pte_none case, but I think the syscall should be different, and it > > shouldn't have anything to do with the nonlinearity (nor with rmap). > > It's obvious what to do about protections. so you agree it'd better be a separate syscall, also given it seems the current remap_file_pages api in 2.5 seems unfortunately already frozen since I think it's wrong as it should only work on VM_NONLINEAR vmas, it's very unclean to allow remap_file_pages to mangle whatever vma out there despite it has to deal with truncate etc.. I think the minium required change to the API is to add a MAP_NONLINEAR that converts in kernel space to a VM_NONLINEAR. You allocate the mapping with mmap(MAP_NONLINAER) and only then remap_file_pages will work. This solves all the current brekages (and it'll be trivial to skip over VM_NONLINEAR in the 2.4 vm too). (then there's the rmap/mlock/munlock issue but that's an implementation issue non visible from userspace [modulo security with the sysctl], this one instead is a API bug IMHO and it'd better be fixed before people puts the backport in production) Again, all in my humble opinion. Andrea -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org