linux-kernel - Re: [PATCH 0 of 4] mm+paravirt+xen: add pte read-modify-write abstraction

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Message-ID: <48372C2F.1090704@goop.org>
Date:	Fri, 23 May 2008 21:42:23 +0100
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	xen-devel <xen-devel@...ts.xensource.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Hugh Dickins <hugh@...itas.com>,
	Zachary Amsden <zach@...are.com>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 0 of 4] mm+paravirt+xen: add pte read-modify-write abstraction

Linus Torvalds wrote:
> On Fri, 23 May 2008, Jeremy Fitzhardinge wrote:
>   
>> This series adds the pte_rmw_start() and pte_rmw_commit() operations,
>> which change this sequence to:
>>
>> 	ptent = pte_rmw_start(mm, addr, pte);
>> 	ptent = pte_modify(ptent, newprot);
>> 	/* ... */
>> 	pte_rmw_commit(mm, addr, pte, ptent);
>>     
>
> Can you please rename these.
>
> It's not a general "read-modify-write" operation on the PTE, and this 
> *only* works for changing protection details. In particular, you cannot 
> use pte_rmw_start/commit to change the actual page. So it's very much 
> about just protection bits.
>   

Well, you could use it to update the page and protection bits while 
preserving the AD bits, but I don't think that's very useful.

> It should probably also be called ptep_xyz(), since it takes a pte 
> pointer, not a pte.
>
> So maybe calling it "ptent = ptep_modify_prot_start(..)" ... 
> "ptep_modify_prot_commit(..)" or something.
>   

Yep, sounds fine to me.

    J

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