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

[David Hildenbrand <david@redhat.com>]

>>>
>>> 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