Messages in this thread | | | Date | Fri, 4 Jul 2003 02:46:41 +0200 | From | Andrea Arcangeli <> | Subject | Re: What to expect with the 2.6 VM |
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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.
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