[PATCH 09/10] Add page_is_buddy for old kernels

[HATAYAMA Daisuke]

On kernels from v2.6.15 to v2.6.17 buddy page is marked by the
condition that PG_private flag is set and _count == 0.

Unfortunately, I have yet to test this logic on these kernel versions
simply because I've been failing to boot them on my box.

Note that on these kernels, free list can be corrupted due to the bug
that the above two conditions are not checked atomically. The reason
why PG_buddy was introduced is a fix for this bug.

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

 makedumpfile.c |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index 838ef53..d1efc09 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3643,6 +3643,20 @@ exclude_free_page(void)
 }
 
 /*
+ * For the kernel versions from v2.6.15 to v2.6.17.
+ */
+static int
+page_is_buddy_v1(unsigned long flags, unsigned int _mapcount,
+			unsigned long private, unsigned int _count)
+{
+	if ((flags & (1UL << NUMBER(PG_private)))
+	    && _count == 0)
+		return TRUE;
+
+	return FALSE;
+}
+
+/*
  * For the kernel versions from v2.6.17 to v2.6.37.
  */
 static int
@@ -3675,8 +3689,9 @@ static void
 setup_page_is_buddy(void)
 {
 	if (NUMBER(PG_buddy) == NOT_FOUND_NUMBER) {
-		if (SIZE(pageflags) != NOT_FOUND_STRUCTURE
-		    && NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) != NOT_FOUND_NUMBER)
+		if (SIZE(pageflags) == NOT_FOUND_STRUCTURE)
+			info->page_is_buddy = page_is_buddy_v1;
+		else if (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; "