[PPC64] Bug fix for hugepages on ppc64

[PPC64] Bug fix for hugepages on ppc64

[David Gibson]

Andrew, please apply.

Currently the flag indicating whether or not hugepages are allowed
below 4GB is not correctly propagated across fork(), which can lead to
oopses.  The patch below fixes this.

diff -urN ppc64-linux-2.5/include/asm-ppc64/mmu_context.h linux-gogogo/include/asm-ppc64/mmu_context.h
--- ppc64-linux-2.5/include/asm-ppc64/mmu_context.h	2003-12-18 09:29:18.000000000 +1100
+++ linux-gogogo/include/asm-ppc64/mmu_context.h	2004-01-19 15:36:43.518987021 +1100
@@ -81,6 +81,8 @@
 {
 	long head;
 	unsigned long flags;
+	/* This does the right thing across a fork (I hope) */
+	unsigned long low_hpages = mm->context & CONTEXT_LOW_HPAGES;
 
 	spin_lock_irqsave(&mmu_context_queue.lock, flags);
 
@@ -91,6 +93,7 @@
 
 	head = mmu_context_queue.head;
 	mm->context = mmu_context_queue.elements[head];
+	mm->context |= low_hpages;
 
 	head = (head < LAST_USER_CONTEXT-1) ? head+1 : 0;
 	mmu_context_queue.head = head;


-- 
David Gibson			| For every complex problem there is a
david AT gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson