[PATCH] [7/16] POISON: Add basic support for poisoned pages in fault handler

[Andi Kleen <andi@firstfloor.org>]

- Add a new VM_FAULT_POISON error code to handle_mm_fault. Right now
architectures have to explicitely enable poison page support, so
this is forward compatible to all architectures. They only need
to add it when they enable poison page support.
- Add poison page handling in swap in fault code

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/mm.h |    3 ++-
 mm/memory.c        |   17 ++++++++++++++---
 2 files changed, 16 insertions(+), 4 deletions(-)

Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c	2009-04-07 16:39:24.000000000 +0200
+++ linux/mm/memory.c	2009-04-07 16:43:06.000000000 +0200
@@ -1315,7 +1315,8 @@
 				if (ret & VM_FAULT_ERROR) {
 					if (ret & VM_FAULT_OOM)
 						return i ? i : -ENOMEM;
-					else if (ret & VM_FAULT_SIGBUS)
+					if (ret &
+					    (VM_FAULT_POISON|VM_FAULT_SIGBUS))
 						return i ? i : -EFAULT;
 					BUG();
 				}
@@ -2426,8 +2427,15 @@
 		goto out;
 
 	entry = pte_to_swp_entry(orig_pte);
-	if (is_migration_entry(entry)) {
-		migration_entry_wait(mm, pmd, address);
+	if (unlikely(non_swap_entry(entry))) {
+		if (is_migration_entry(entry)) {
+			migration_entry_wait(mm, pmd, address);
+		} else if (is_poison_entry(entry)) {
+			ret = VM_FAULT_POISON;
+		} else {
+			print_bad_pte(vma, address, pte, NULL);
+			ret = VM_FAULT_OOM;
+		}
 		goto out;
 	}
 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
@@ -2451,6 +2459,9 @@
 		/* Had to read the page from swap area: Major fault */
 		ret = VM_FAULT_MAJOR;
 		count_vm_event(PGMAJFAULT);
+	} else if (PagePoison(page)) {
+		ret = VM_FAULT_POISON;
+		goto out;
 	}
 
 	lock_page(page);
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h	2009-04-07 16:39:24.000000000 +0200
+++ linux/include/linux/mm.h	2009-04-07 16:43:05.000000000 +0200
@@ -702,11 +702,12 @@
 #define VM_FAULT_SIGBUS	0x0002
 #define VM_FAULT_MAJOR	0x0004
 #define VM_FAULT_WRITE	0x0008	/* Special case for get_user_pages */
+#define VM_FAULT_POISON 0x0010	/* Hit poisoned page */
 
 #define VM_FAULT_NOPAGE	0x0100	/* ->fault installed the pte, not return page */
 #define VM_FAULT_LOCKED	0x0200	/* ->fault locked the returned page */
 
-#define VM_FAULT_ERROR	(VM_FAULT_OOM | VM_FAULT_SIGBUS)
+#define VM_FAULT_ERROR	(VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_POISON)
 
 /*
  * Can be called by the pagefault handler when it gets a VM_FAULT_OOM.