[PATCH 08/10] Add page_is_buddy for PG_buddy

[HATAYAMA Daisuke]

On kernels from v2.6.18 to v2.6.37, buddy page is marked by the
PG_buddy flag.

  kernel version     | PG_buddy
  ------------------ +---------------------------------
  v2.6.17 to v2.6.26 | 19
  v2.6.27 to v2.6.37 | 19 if CONFIG_PAGEFLAGS_EXTEND=y
                     | 18 otherwise

Note for hard coding: alghouth I don't do in this patch set, it's
possible to determine whether CONFIG_PAGEFLAGS_EXTEND=yes or not by
looking at error_status array defined in mm/memory-failure.c, for
example.

Signed-off-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
---

 makedumpfile.c |   30 +++++++++++++++++++++++-------
 1 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index 27ad3e6..838ef53 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3643,6 +3643,19 @@ exclude_free_page(void)
 }
 
 /*
+ * For the kernel versions from v2.6.17 to v2.6.37.
+ */
+static int
+page_is_buddy_v2(unsigned long flags, unsigned int _mapcount,
+			unsigned long private, unsigned int _count)
+{
+	if (flags & (1UL << NUMBER(PG_buddy)))
+		return TRUE;
+
+	return FALSE;
+}
+
+/*
  * For v2.6.38 and later kernel versions.
  */
 static int
@@ -3661,13 +3674,16 @@ page_is_buddy_v3(unsigned long flags, unsigned int _mapcount,
 static void
 setup_page_is_buddy(void)
 {
-	if (NUMBER(PG_buddy) == NOT_FOUND_NUMBER
-	    && SIZE(pageflags) != NOT_FOUND_STRUCTURE
-	    && NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) != NOT_FOUND_NUMBER)
-		info->page_is_buddy = page_is_buddy_v3;
-	else
-		MSG("Can't select page_is_buddy handler; "
-		    "filtering free pages is disabled.\n");
+	if (NUMBER(PG_buddy) == NOT_FOUND_NUMBER) {
+		if (SIZE(pageflags) != NOT_FOUND_STRUCTURE
+		    && NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) != NOT_FOUND_NUMBER)
+			info->page_is_buddy = page_is_buddy_v3;
+		else {
+			MSG("Can't select page_is_buddy handler; "
+			    "filtering free pages is disabled.\n");
+		}
+	} else
+		info->page_is_buddy = page_is_buddy_v2;
 }
 
 /*