linux-kernel - Re: hmm pud-entry callback locking?

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Message-ID: <20191007141919.GA3222@redhat.com>
Date:   Mon, 7 Oct 2019 10:19:19 -0400
From:   Jerome Glisse <jglisse@...hat.com>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
Cc:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: hmm pud-entry callback locking?

On Sat, Oct 05, 2019 at 02:29:40PM +0200, Thomas Hellström (VMware) wrote:
> Hi, Jerome,
> 
> I was asked by Kirill to try to unify the pagewalk pud_entry and pmd_entry
> callbacks. The only user of the pagewalk pud-entry is currently hmm.
> 
> But the pagewalk code call pud_entry only for huge puds with the page-table
> lock held, whereas the hmm callback appears to assume it gets called
> unconditionally without the page-table lock held?
> 
> Could you shed some light into this?

I think in my mind they were already unified :) I think easiest thing is
to remove the hmm pud walker, this is not a big deal this will break huge
pud for now, we can re-add this to hmm once you unified them.

Cheers,
Jérôme