[RFC PATCH 07/10] Add excldue free pages by looking up mem_map array

[HATAYAMA Daisuke]

Add free page filtering logic in the processing looking up mem_map
array. page_is_buddy handler is newly introduced, which abstracts
condition of determining buddy page that varies depending on kernel
versions. On makedumpfile suppoting range of kernel versions, there
are three kinds of page_is_buddy, which are introduced in later
patches. Also, _mapcount and private fields of page struct are newly
introduced, which are used in the page_is_buddy handlers.

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

 makedumpfile.c |   21 ++++++++++++++++++---
 makedumpfile.h |    6 ++++++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index d1eded0..37c371e 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -3689,8 +3689,8 @@ __exclude_unnecessary_pages(unsigned long mem_map,
 	unsigned long long pfn_read_start, pfn_read_end, index_pg;
 	unsigned char page_cache[SIZE(page) * PGMM_CACHED];
 	unsigned char *pcache;
-	unsigned int _count;
-	unsigned long flags, mapping;
+	unsigned int _count, _mapcount;
+	unsigned long flags, mapping, private;
 
 	/*
 	 * Refresh the buffer of struct page, when changing mem_map.
@@ -3738,11 +3738,26 @@ __exclude_unnecessary_pages(unsigned long mem_map,
 		flags   = ULONG(pcache + OFFSET(page.flags));
 		_count  = UINT(pcache + OFFSET(page._count));
 		mapping = ULONG(pcache + OFFSET(page.mapping));
+		_mapcount = UINT(pcache + OFFSET(page._mapcount));
+		private = ULONG(pcache + OFFSET(page.private));
 
+ 		/*
+		 * Exclude the free page managed by a buddy.
+		 */
+		if ((info->dump_level & DL_EXCLUDE_FREE_CONST)
+		    && info->page_is_buddy
+		    && info->page_is_buddy(flags, _mapcount, private,
+					   _count)) {
+			int i;
+
+			for (i = 0; i < (1<<private); ++i)
+				clear_bit_on_2nd_bitmap_for_kernel(pfn + i);
+			pfn_free += i;
+		}
 		/*
 		 * Exclude the cache page without the private page.
 		 */
-		if ((info->dump_level & DL_EXCLUDE_CACHE)
+		else if ((info->dump_level & DL_EXCLUDE_CACHE)
 		    && (isLRU(flags) || isSwapCache(flags))
 		    && !isPrivate(flags) && !isAnon(mapping)) {
 			clear_bit_on_2nd_bitmap_for_kernel(pfn);
diff --git a/makedumpfile.h b/makedumpfile.h
index 404f00e..d867dfe 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -943,6 +943,12 @@ struct DumpInfo {
 	 */
 	int flag_sadump_diskset;
 	enum sadump_format_type flag_sadump;         /* sadump format type */
+
+	/*
+	 * for filtering free pages managed by buddy system:
+	 */
+	int (*page_is_buddy)(unsigned long flags, unsigned int _mapcount,
+			     unsigned long private, unsigned int _count);
 };
 extern struct DumpInfo		*info;