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SubjectRe: [PATCH 00/28] Swap over NFS -v16
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> > > > mm-page_file_methods.patch
> > > >
> > > > This makes page_offset and others more expensive by adding a
> > > > conditional jump to a function call that is not usually made.
> > > >
> > > > Why do swap pages have a different index to everyone else?
> > >
> > > Because the page->index of an anonymous page is related to its (anon)vma
> > > so that it satisfies the constraints for vm_normal_page().
> > >
> > > The index in the swap file it totally unrelated and quite random. Hence
> > > the swap-cache uses page->private to store it in.
> >
> > Yeah, and putting the condition into page_offset() will confuse code
> > which uses it for finding the offset in the VMA or in a tmpfs file.
> >
> > So why not just have a separate page_swap_offset() function, used
> > exclusively by swap_in/out()?
>
> Ah, we can do the page_file_offset() to match page_file_index() and
> page_file_mapping(). And convert NFS to use page_file_offset() where
> appropriate, as I already did for these others.
>
> That would sort out the mess, right?

Yes, that sounds perfect.

Miklos


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