Re: [PATCH bpf-next 03/16] mm: Expose vmap_pages_range() to the rest of the kernel.

[Christoph Hellwig <hch@infradead.org>]

On Wed, Feb 07, 2024 at 09:07:51PM +0000, Lorenzo Stoakes wrote:
> > memory region between bpf program and user space process.
> > It will function similar to vmalloc()/vm_map_ram():
> > - get_vm_area()
> > - alloc_pages()
> > - vmap_pages_range()
> 
> This tells me absolutely nothing about why it is justified to expose this
> internal interface. You need to put more explanation here along the lines
> of 'we had no other means of achieving what we needed from vmalloc because
> X, Y, Z and are absolutely convinced it poses no risk of breaking anything'.
> 
> I mean I see a lot of checks in vmap() that aren't in vmap_pages_range()
> for instance. We good to expose that, not only for you but for any other
> core kernel users?

And as someone who has reviewed these same thing before:

hard NAK.  We need to keep vmalloc internals internal and not start
poking holes into the abstractions after we've got them roughly into
shape.