On kernels from v2.6.38 and later kernels, buddy page is marked by
_mapcount == PAGE_BUDDY_MAPCOUNT_VALUE, which varies once as follows:
kernel version | PAGE_BUDDY_MAPCOUNT_VALUE
------------------+--------------------------
v2.6.38 | -2
v2.6.39 and later | -128
One more notice is that _mapcount shares its memory with other fields
for SLAB/SLUB when PG_slab is set. Before looking up _mapcount value,
we need to check if PG_slab is set.
Signed-off-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
---
makedumpfile.c | 25 +++++++++++++++++++++++--
1 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/makedumpfile.c b/makedumpfile.c
index 6358fc0..27ad3e6 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3642,11 +3642,32 @@ exclude_free_page(void)
return TRUE;
}
+/*
+ * For v2.6.38 and later kernel versions.
+ */
+static int
+page_is_buddy_v3(unsigned long flags, unsigned int _mapcount,
+ unsigned long private, unsigned int _count)
+{
+ if (flags & (1UL << NUMBER(PG_slab)))
+ return FALSE;
+
+ if (_mapcount == (int)NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE))
+ return TRUE;
+
+ return FALSE;
+}
+
static void
setup_page_is_buddy(void)
{
- MSG("Can't select page_is_buddy handler; "
- "filtering free pages is disabled.\n");
+ 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");
}
/*
