Re: [PATCH 1/4] mm: Introduce vm_uffd_ops API

[David Hildenbrand]

> > > How about an updated commit like this?
> > >
> > >     Currently, most of the userfaultfd features are implemented directly in the
> > >     core mm.  It will invoke VMA specific functions whenever necessary.  So far
> > >     it is fine because it almost only interacts with shmem and hugetlbfs.
> > >
> > >     This patch introduces a generic userfaultfd API for vm_operations_struct,
> > >     so that any type of file (including kernel modules that can be compiled
> > >     separately from the kernel core) can support userfaults without modifying
> > >     the core files.
> >
> > .... is it really "any file" ? I doubt it, but you likely have a better idea
> > on how it all could just work with "any file".
> >
> > >     After this API applied, if a module wants to support userfaultfd, the
> > >     module should only need to touch its own file and properly define
> > >     vm_uffd_ops, instead of changing anything in core mm.
> > >
> > >     ...
> >
> > Talking about files and modules is still confusing I'm afraid. It's really a
> > special-purpose file (really, not any ordinary files on ordinary
> > filesystems), no?
>
> One major reason I wanted to avoid the term "in-memory" is that we already
> support most of the files on WP_ASYNC, so emphasizing on in-memory might be
> misleading, even though WP_ASYNC isn't much taken into the picture of the
> vm_uffd_ops being proposed.

Oh, yes, agreed on WP_ASYNC. But they would not be using the vma_ops 
thingy, right?

--
Cheers,

David / dhildenb