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. We need to check if PG_slab is set
or not before looking up _mapcount value.
Signed-off-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
---
makedumpfile.c | 30 ++++++++++++++++++++++++++++++
1 files changed, 30 insertions(+), 0 deletions(-)
diff --git a/makedumpfile.c b/makedumpfile.c
index 37c371e..aea956f 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -55,6 +55,8 @@ do { \
*ptr_long_table = value; \
} while (0)
+static void setup_page_is_buddy(void);
+
void
initialize_tables(void)
{
@@ -2733,6 +2735,9 @@ out:
if (!get_value_for_old_linux())
return FALSE;
+ if (info->dump_level & DL_EXCLUDE_FREE_CONST)
+ setup_page_is_buddy();
+
return TRUE;
}
@@ -3512,6 +3517,31 @@ exclude_free_page(void)
return TRUE;
}
+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)
+{
+ 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;
+
+ MSG("Can't select page_is_buddy handler; "
+ "filtering free pages is disabled.\n");
+}
+
/*
* If using a dumpfile in kdump-compressed format as a source file
* instead of /proc/vmcore, 1st-bitmap of a new dumpfile must be
