[PATCH 2/4] Verify the page links and memory model

[Mel Gorman]

This patch prints out information on how the page flags are being used and
verifies they are correct if mminit_debug_level is MMINIT_VERIFY or higher.
When the page flags are updated with section, node and zone information, an
additional check is made to ensure the values can be retrieved correctly. The
final check made with respect to pages is that pfn_to_page() and page_to_pfn()
are returning sensible values.

Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
---

 mm/internal.h   |   12 +++++++++
 mm/mm_init.c    |   64 +++++++++++++++++++++++++++++++++++++++++++++++++++
 mm/page_alloc.c |    6 ++++
 3 files changed, 82 insertions(+)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.25-rc9-0010_mminit_debug_framework/mm/internal.h linux-2.6.25-rc9-0020_memmap_init_debug/mm/internal.h
--- linux-2.6.25-rc9-0010_mminit_debug_framework/mm/internal.h	2008-04-17 00:20:19.000000000 +0100
+++ linux-2.6.25-rc9-0020_memmap_init_debug/mm/internal.h	2008-04-17 00:20:33.000000000 +0100
@@ -78,6 +78,10 @@ do { \
 	} \
 } while (0)
 
+extern void mminit_verify_pageflags(void);
+extern void mminit_verify_page_links(struct page *page,
+		enum zone_type zone, unsigned long nid, unsigned long pfn);
+
 #else
 
 static inline void mminit_debug_printk(unsigned int level, const char *prefix,
@@ -85,5 +89,13 @@ static inline void mminit_debug_printk(u
 {
 }
 
+static inline void mminit_verify_pageflags(void)
+{
+}
+
+static inline void mminit_verify_page_links(struct page *page,
+		enum zone_type zone, unsigned long nid, unsigned long pfn)
+{
+}
 #endif /* CONFIG_DEBUG_MEMORY_INIT */
 #endif
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.25-rc9-0010_mminit_debug_framework/mm/mm_init.c linux-2.6.25-rc9-0020_memmap_init_debug/mm/mm_init.c
--- linux-2.6.25-rc9-0010_mminit_debug_framework/mm/mm_init.c	2008-04-17 00:20:19.000000000 +0100
+++ linux-2.6.25-rc9-0020_memmap_init_debug/mm/mm_init.c	2008-04-17 00:20:33.000000000 +0100
@@ -7,9 +7,73 @@
  */
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include "internal.h"
 
 int __initdata mminit_debug_level;
 
+void __init mminit_verify_pageflags(void)
+{
+	unsigned long shift;
+	if (mminit_debug_level < MMINIT_VERIFY)
+		return;
+
+	mminit_debug_printk(MMINIT_TRACE, "pageflags_layout_widths",
+		"Section %d Node %d Zone %d Reserved %d\n",
+		SECTIONS_WIDTH,
+		NODES_WIDTH,
+		ZONES_WIDTH,
+		FLAGS_RESERVED);
+	mminit_debug_printk(MMINIT_TRACE, "pageflags_layout_shifts",
+		"Section %d Node %d Zone %d\n",
+#ifdef SECTIONS_SHIFT
+		SECTIONS_SHIFT,
+#else
+		0,
+#endif
+		NODES_SHIFT,
+		ZONES_SHIFT);
+	mminit_debug_printk(MMINIT_TRACE, "pageflags_layout_offsets",
+		"Section %d Node %d Zone %d\n",
+		SECTIONS_PGSHIFT,
+		NODES_PGSHIFT,
+		ZONES_PGSHIFT);
+	mminit_debug_printk(MMINIT_TRACE, "pageflags_layout_zoneid",
+		"Zone ID: %d -> %d\n",
+		ZONEID_PGOFF, ZONEID_PGOFF + ZONEID_SHIFT);
+#ifdef NODE_NOT_IN_PAGE_FLAGS
+	mminit_debug_printk(MMINIT_TRACE, "pageflags_layout_nodeflags",
+		"Node not in page flags");
+#endif
+
+	shift = 8 * sizeof(unsigned long);
+	if (SECTIONS_WIDTH) {
+		shift -= SECTIONS_WIDTH;
+		BUG_ON(shift != SECTIONS_PGSHIFT);
+	}
+	if (NODES_WIDTH) {
+		shift -= NODES_WIDTH;
+		BUG_ON(shift != NODES_PGSHIFT);
+	}
+	if (ZONES_WIDTH) {
+		shift -= ZONES_WIDTH;
+		BUG_ON(shift != ZONES_PGSHIFT);
+	}
+	BUG_ON((ZONES_MASK << ZONES_PGSHIFT) &
+			(NODES_MASK << NODES_PGSHIFT) &
+			(SECTIONS_MASK << SECTIONS_PGSHIFT));
+}
+
+void __meminit mminit_verify_page_links(struct page *page, enum zone_type zone,
+			unsigned long nid, unsigned long pfn)
+{
+	if (mminit_debug_level < MMINIT_VERIFY)
+		return;
+
+	BUG_ON(page_to_nid(page) != nid);
+	BUG_ON(page_zonenum(page) != zone);
+	BUG_ON(page_to_pfn(page) != pfn);
+}
+
 static __init int set_mminit_debug_level(char *str)
 {
 	get_option(&str, &mminit_debug_level);
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.25-rc9-0010_mminit_debug_framework/mm/page_alloc.c linux-2.6.25-rc9-0020_memmap_init_debug/mm/page_alloc.c
--- linux-2.6.25-rc9-0010_mminit_debug_framework/mm/page_alloc.c	2008-04-17 00:20:19.000000000 +0100
+++ linux-2.6.25-rc9-0020_memmap_init_debug/mm/page_alloc.c	2008-04-17 00:20:33.000000000 +0100
@@ -2533,6 +2533,7 @@ void __meminit memmap_init_zone(unsigned
 		}
 		page = pfn_to_page(pfn);
 		set_page_links(page, zone, nid, pfn);
+		mminit_verify_page_links(page, zone, nid, pfn);
 		init_page_count(page);
 		reset_page_mapcount(page);
 		SetPageReserved(page);
@@ -2829,6 +2830,10 @@ __meminit int init_currently_empty_zone(
 
 	zone->zone_start_pfn = zone_start_pfn;
 
+	mminit_debug_printk(MMINIT_TRACE, "memmap_init",
+			"Initialising map node %d zone %d pfns %lu -> %lu\n",
+			pgdat->node_id, zone_idx(zone),
+			zone_start_pfn, (zone_start_pfn + size));
 	memmap_init(size, pgdat->node_id, zone_idx(zone), zone_start_pfn);
 
 	zone_init_free_lists(zone);
@@ -3896,6 +3901,7 @@ void __init free_area_init_nodes(unsigne
 						early_node_map[i].end_pfn);
 
 	/* Initialise every node */
+	mminit_verify_pageflags();
 	setup_nr_node_ids();
 	for_each_online_node(nid) {
 		pg_data_t *pgdat = NODE_DATA(nid);
--
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