linux-kernel - Re: [RFC PATCH v4 09/27] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY

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Message-ID: <688c3f90-f86e-32e8-ce1a-7a10facb08a8@linux.intel.com>
Date:   Wed, 3 Oct 2018 07:05:23 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v4 09/27] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW

On 10/03/2018 06:38 AM, Matthew Wilcox wrote:
> On Fri, Sep 21, 2018 at 08:03:33AM -0700, Yu-cheng Yu wrote:
>> We are going to create _PAGE_DIRTY_SW for non-hardware, memory
>> management purposes.  Rename _PAGE_DIRTY to _PAGE_DIRTY_HW and
>> _PAGE_BIT_DIRTY to _PAGE_BIT_DIRTY_HW to make these PTE dirty
>> bits more clear.  There are no functional changes in this
>> patch.
> I would like there to be some documentation in this patchset which
> explains the difference between PAGE_SOFT_DIRTY and PAGE_DIRTY_SW.
> 
> Also, is it really necessary to rename PAGE_DIRTY?  It feels like a
> lot of churn.

This is a lot of churn?  Are we looking a the same patch? :)

 arch/x86/include/asm/pgtable.h       |  6 +++---
 arch/x86/include/asm/pgtable_types.h | 17 +++++++++--------
 arch/x86/kernel/relocate_kernel_64.S |  2 +-
 arch/x86/kvm/vmx.c                   |  2 +-
 4 files changed, 14 insertions(+), 13 deletions(-)

But, yeah, I think we need to.  While it will take a little adjustment
in the brains of us old-timers and a bit of pain when switching from old
kernels to new, this makes it a lot more clear what is going on.