pagemap: export KPF_HWPOISON

This flag indicates a hardware detected memory corruption on the page.
Any future access of the page data may bring down the machine.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/vm/page-types.c

@@ -69,6 +69,7 @@
 #define KPF_COMPOUND_TAIL	16
 #define KPF_HUGE		17
 #define KPF_UNEVICTABLE		18
+#define KPF_HWPOISON		19
 #define KPF_NOPAGE		20
 
 /* [32-] kernel hacking assistances */
@@ -116,6 +117,7 @@ static char *page_flag_names[] = {
 	[KPF_COMPOUND_TAIL]	= "T:compound_tail",
 	[KPF_HUGE]		= "G:huge",
 	[KPF_UNEVICTABLE]	= "u:unevictable",
+	[KPF_HWPOISON]		= "X:hwpoison",
 	[KPF_NOPAGE]		= "n:nopage",
 
 	[KPF_RESERVED]		= "r:reserved",

Documentation/vm/pagemap.txt

@@ -57,6 +57,7 @@ There are three components to pagemap:
     16. COMPOUND_TAIL
     16. HUGE
     18. UNEVICTABLE
+    19. HWPOISON
     20. NOPAGE
 
 Short descriptions to the page flags:
@@ -86,6 +87,9 @@ Short descriptions to the page flags:
 17. HUGE
     this is an integral part of a HugeTLB page
 
+19. HWPOISON
+    hardware detected memory corruption on this page: don't touch the data!
+
 20. NOPAGE
     no page frame exists at the requested address
 

fs/proc/page.c

@@ -94,6 +94,7 @@ static const struct file_operations proc_kpagecount_operations = {
 #define KPF_COMPOUND_TAIL	16
 #define KPF_HUGE		17
 #define KPF_UNEVICTABLE		18
+#define KPF_HWPOISON		19
 #define KPF_NOPAGE		20
 
 #define KPF_KSM			21
@@ -180,6 +181,10 @@ static u64 get_uflags(struct page *page)
 	u |= kpf_copy_bit(k, KPF_UNEVICTABLE,	PG_unevictable);
 	u |= kpf_copy_bit(k, KPF_MLOCKED,	PG_mlocked);
 
+#ifdef CONFIG_MEMORY_FAILURE
+	u |= kpf_copy_bit(k, KPF_HWPOISON,	PG_hwpoison);
+#endif
+
 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 	u |= kpf_copy_bit(k, KPF_UNCACHED,	PG_uncached);
 #endif