When c_p_a() detects a inconsistency in the kernel page tables
it BUGs. When this happens dump the page table first to avoid one
bug reporting round trip.
Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Jan Beulich <jbeulich@novell.com>
---
arch/x86/mm/pageattr_32.c | 11 ++++++++++-
arch/x86/mm/pageattr_64.c | 11 ++++++++++-
2 files changed, 20 insertions(+), 2 deletions(-)
Index: linux/arch/x86/mm/pageattr_64.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr_64.c
+++ linux/arch/x86/mm/pageattr_64.c
@@ -12,6 +12,7 @@
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/io.h>
+#include <asm/kdebug.h>
enum flush_mode { FLUSH_NONE, FLUSH_CACHE, FLUSH_TLB };
@@ -231,8 +232,16 @@ __change_page_attr(unsigned long address
set_pte(kpte, pfn_pte(pfn, ref_prot));
BUG_ON(page_private(kpte_page) == 0);
page_private(kpte_page)--;
- } else
+ } else {
+ /*
+ * When you're here you either set the same page to PAGE_KERNEL
+ * two times in a row or the page table reference counting is
+ * broken again. To catch the later bug for now (sorry)
+ */
+ printk(KERN_ERR "address %lx\n", address);
+ dump_pagetable(address);
BUG();
+ }
save_page(kpte_page);
if (!PageReserved(kpte_page) && page_private(kpte_page) == 0)
Index: linux/arch/x86/mm/pageattr_32.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr_32.c
+++ linux/arch/x86/mm/pageattr_32.c
@@ -13,6 +13,7 @@
#include <asm/tlbflush.h>
#include <asm/pgalloc.h>
#include <asm/sections.h>
+#include <asm/kdebug.h>
#define PG_deferred PG_arch_1
@@ -252,8 +253,16 @@ __change_page_attr(struct page *page, pg
set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
BUG_ON(page_private(kpte_page) == 0);
page_private(kpte_page)--;
- } else
+ } else {
+ /*
+ * When you're here you either set the same page to PAGE_KERNEL
+ * two times in a row or the page table reference counting is
+ * broken again. To catch the later bug for now (sorry)
+ */
+ printk(KERN_ERR "address %lx\n", address);
+ dump_pagetable(address);
BUG();
+ }
/*
* If the pte was reserved, it means it was created at boot
--
