xen: disable split pte locks for now
xen: disable split pte locks for now

When pinning and unpinning pagetables, we must protect them against
being used by other CPUs, lest they see the pagetable in an
intermediate read-only-but-not-pinned state.

When using split pte locks, doing this properly would require taking
all the pte locks for the pagetable while pinning, but this may overflow
the PREEMPT_BITS part of the preempt counter if the process has mapped
more than about 512M of memory.

However, failing to take the pte locks causes write-protect faults when
the pageout code is trying to clear the Access bit on a pte which is part
of a freshy created and still being pinned process after fork.

This is a short-term fix until the problem is solved properly.

Signed-off-by: Jeremy Fitzhardinge <b3f594e10a9edcf5413cf1190121d45078c62290@xensource.com>
Acked-by: Rik van Riel <a21938f5d463ddf41aa718934c205ca2cce8ebbc@redhat.com>
Acked-by: Hugh Dickins <a6c5230a10c458028ff1bd5985dd47c394028d47@veritas.com>
Cc: David Rientjes <d8cd2994e15bc61ddb2b113030bda55eebc3a0fe@google.com>
Cc: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Cc: Andi Kleen <0474aee45985f5ae829f53849df476200e876990@suse.de>
Cc: Keir Fraser <69344103cc60b36d6e1fbdc31ce6504b2286c646@xensource.com>
Cc: Jan Beulich <01de09643e0ae62e116f8bd77de435799874b456@novell.com>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas