linux-kernel - Re: [PATCH 2/3] hugetlb: Use vmf_anon_prepare() instead of anon_vma

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Date: Wed, 21 Feb 2024 10:02:43 -0800
From: Vishal Moola <vishal.moola@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	akpm@...ux-foundation.org, muchun.song@...ux.dev
Subject: Re: [PATCH 2/3] hugetlb: Use vmf_anon_prepare() instead of anon_vma_prepare()

On Wed, Feb 21, 2024 at 9:55 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Wed, Feb 21, 2024 at 09:15:51AM -0800, Vishal Moola wrote:
> > > >       unsigned long haddr = address & huge_page_mask(h);
> > > >       struct mmu_notifier_range range;
> > > > +     struct vm_fault vmf = {
> > > > +                             .vma = vma,
> > > > +                             .address = haddr,
> > > > +                             .real_address = address,
> > > > +                             .flags = flags,
> > > > +     };
> > >
> > > We don't usually indent quite so far.  One extra tab would be enough.
> > >
> > > Also, I thought we talked about creating the vmf in hugetlb_fault(),
> > > then passing it to hugetlb_wp() hugetlb_no_page() and handle_userfault()?
> > > Was there a reason to abandon that idea?
> >
> > No I haven't abandoned that idea, I intend to have a separate patchset to go
> > on top of this one - just keeping them separate since they are conceptually
> > different. I'm converting each function to use struct vm_fault first, then
> > shifting it to be passed throughout as an arguement while cleaning up the
> > excess variables laying around. In a sense working bottom-up instead
> > of top-down.
>
> I think you'll find it less work to create it in hugetlb_fault()
> first.  ie patch 2 could be to hoist its creation from half-way down
> hugetlb_fault to the top of hugetlb_fault.  Patch 3 could pass it
> through hugetlb_no_page() to hugetlb_handle_userfault() and remove its
> creation there.  Now you've alreedy got it, and can make use of it in
> this patch which would be the new patch 4.

Ah I see, that way would definitely be a lot less work. I'll make that
change for this patchset in v2 then.

> If you want to do a cleanup patch afterwards, you could hoist the vmf
> creation all the way to handle_mm_fault() ;-)

Yeah, I was already looking at doing that in the future patchset :)