Messages in this thread | | | Date | Sat, 7 Oct 2006 13:44:07 -0700 | From | Andrew Morton <> | Subject | Re: [patch 3/3] mm: fault handler to replace nopage and populate |
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On Sat, 7 Oct 2006 15:06:32 +0200 (CEST) Nick Piggin <npiggin@suse.de> wrote:
> Nonlinear mappings are (AFAIKS) simply a virtual memory concept that > encodes the virtual address -> file offset differently from linear > mappings. > > I can't see why the filesystem/pagecache code should need to know anything > about it, except for the fact that the ->nopage handler didn't quite pass > down enough information (ie. pgoff). But it is more logical to pass pgoff > rather than have the ->nopage function calculate it itself anyway. And > having the nopage handler install the pte itself is sort of nasty. > > This patch introduces a new fault handler that replaces ->nopage and ->populate > and (hopefully) ->page_mkwrite. Most of the old mechanism is still in place > so there is a lot of duplication and nice cleanups that can be removed if > everyone switches over. > > The rationale for doing this in the first place is that nonlinear mappings > are subject to the pagefault vs invalidate/truncate race too, and it seemed > stupid to duplicate the synchronisation logic rather than just consolidate > the two.
- You may find that gcc generates crap code for the initialisation of the `struct fault_data'. If so, filling the fields in by hand one-at-a-time will improve things.
- So is the plan here to migrate all code over to using vm_operations.fault() and to finally remove vm_operations.nopage and .nopfn? If so, that'd be nice.
- As you know, there is a case for constructing that `struct fault_data' all the way up in do_no_page(): so we can pass data back, asking do_no_page() to rerun the fault if we dropped mmap_sem.
- No useful opinion on the substance of this patch, sorry. It's Saturday ;)
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