Re: What to expect with the 2.6 VM

From: William Lee Irwin III (
Date: Thu Jul 03 2003 - 20:36:12 EST

On Thu, Jul 03, 2003 at 03:21:13PM -0700, William Lee Irwin III wrote:
>> It's obvious what to do about protections.

On Fri, Jul 04, 2003 at 02:46:41AM +0200, Andrea Arcangeli wrote:
> 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)

sys_chattr_file_pages() etc. sounds fine to me; GC's would love it.

I'll tackle the rest in another (somewhat more inflammatory) post.

-- wli
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