linux-kernel - Re: [PATCH RFC] use of activate_mm in fs/aio.c:use

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Message-ID: <45777002.6050009@goop.org>
Date:	Wed, 06 Dec 2006 17:36:02 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Zach Brown <zach.brown@...cle.com>,
	Badari Pulavarty <pbadari@...ibm.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Zachary Amsden <zach@...are.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jeff Dike <jdike@...toit.com>
Subject: Re: [PATCH RFC] use of activate_mm in fs/aio.c:use_mm()?

Jeremy Fitzhardinge wrote:
> I'm wondering if activate_mm() is the right thing to be using in
> use_mm(); shouldn't this be switch_mm()?
>
> On normal x86, they're synonymous, but for the Xen patches I'm adding a
> hook which assumes that activate_mm is only used the first time a new mm
> is used after creation (I have another hook for dealing with dup_mm).  I
> think this use of activate_mm() is the only place where it could be used
> a second time on an mm.
>
> From a quick look at the other architectures I think this is OK (most
> simply implement one in terms of the other), but some are doing some
> subtly different stuff between the two.
>
> Thanks,
>     J
>
>
>   
Er, lets try that again:

diff -r 455b71ed4525 fs/aio.c
--- a/fs/aio.c	Wed Dec 06 13:16:42 2006 -0800
+++ b/fs/aio.c	Wed Dec 06 17:17:43 2006 -0800
@@ -588,7 +588,7 @@ static void use_mm(struct mm_struct *mm)
 	 * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
 	 * it won't work. Update it accordingly if you change it here
 	 */
-	activate_mm(active_mm, mm);
+	switch_mm(active_mm, mm, tsk);
 	task_unlock(tsk);
 
 	mmdrop(active_mm);


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