[PATCH] Use activate_mm() in fs/aio.c:use_mm()

activate_mm() is not the right thing to be using in use_mm().  It should 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.

Acked-by: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/aio.c

@@ -586,7 +586,7 @@ 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);