Re: [PATCH v2] mm: Introduce new function vm_insert_kmem_page

[Souptick Joarder]

On Sat, Oct 6, 2018 at 4:19 PM Miguel Ojeda
<miguel.ojeda.sandonis@xxxxxxxxx> wrote:
>
> On Sat, Oct 6, 2018 at 7:11 AM Souptick Joarder <jrdr.linux@xxxxxxxxx> wrote:
> >
> > On Fri, Oct 5, 2018 at 11:39 PM Miguel Ojeda
> > <miguel.ojeda.sandonis@xxxxxxxxx> wrote:
> > > They are not supposed to be "steps". You did it with 70+ commits (!!)
> > > over the course of several months. Why a tree wasn't created, stuff
> > > developed there, and when done, submitted it for review?
> >
> > Because we already have a plan for entire vm_fault_t migration and
> > the * instruction * was to send one patch per driver.
>
> The instruction?

Sorry for the delayed response.
Instruction from Matthew  Wilcox who is supervising the entire vm_fault_t
migration work :-)

>
> > >
> > > Fine, but you haven't answered to the other parts of my email: you
> > > don't explain why you choose one alternative over the others, you
> > > simply keep changing the approach.
> >
> > We are going in circles here. That you want to convert vm_insert_page
> > to vmf_insert_page for the PF case is fine and understood. However,
> > you don't *need* to introduce a new name for the remaining non-PF
> > cases if the function is going to be the exact same thing as before.
> > You say "The final goal is to remove vm_insert_page", but you haven't
> > justified *why* you need to remove that name.
> >
> > I think I have given that answer. If we don't remove vm_insert_page,
> > future #PF caller will have option to use it. But those should be
> > restricted. How are we going to restrict vm_insert_page in one half
> > of kernel when other half is still using it  ?? Is there any way ? ( I don't
> > know)
>
> Ah, so that is what you are concerned about: future misuses. Well, I
> don't really see the problem. There are only ~18 calls to
> vm_insert_page() in the entire kernel: checking if people is using it
> properly for a while should be easy. As long as the new behavior is
> documented properly, it should be fine. If you are really concerned
> about mistakes being made, then fine, we can rename it as I suggested.
>
> Now, the new vm_insert_range() is another topic. It simplifies a few
> of the callers and buys us the rename at the same time, so I am also
> OK with it.
>
> As you see, I am not against the changes -- it is just that they
> should clearly justified. :-) It wasn't clear what your problem with
> the current vm_insert_page() is.
>
> Cheers,
> Miguel