commit bdc8cb984576ab5b550c8b24c6fa111a873503e3
author Dave Hansen <haveblue@us.ibm.com> Sat Oct 29 18:16:53 2005 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> Sat Oct 29 21:40:44 2005 -0700
tree f94548988874caa10d770e6e65bc50c925abf825
parent 208d54e5513c0c02d85af0990901354c74364d5c

[PATCH] memory hotplug locking: zone span seqlock

See the "fixup bad_range()" patch for more information, but this actually
creates a the lock to protect things making assumptions about a zone's size
staying constant at runtime.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 32fad6d..817635f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -33,6 +33,7 @@
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
 #include <linux/cpuset.h>
+#include <linux/memory_hotplug.h>
 #include <linux/nodemask.h>
 #include <linux/vmalloc.h>
 
@@ -80,12 +81,19 @@
 
 static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 {
-	if (page_to_pfn(page) >= zone->zone_start_pfn + zone->spanned_pages)
-		return 1;
-	if (page_to_pfn(page) < zone->zone_start_pfn)
-		return 1;
+	int ret = 0;
+	unsigned seq;
+	unsigned long pfn = page_to_pfn(page);
 
-	return 0;
+	do {
+		seq = zone_span_seqbegin(zone);
+		if (pfn >= zone->zone_start_pfn + zone->spanned_pages)
+			ret = 1;
+		else if (pfn < zone->zone_start_pfn)
+			ret = 1;
+	} while (zone_span_seqretry(zone, seq));
+
+	return ret;
 }
 
 static int page_is_consistent(struct zone *zone, struct page *page)
@@ -1980,6 +1988,7 @@
 		zone->name = zone_names[j];
 		spin_lock_init(&zone->lock);
 		spin_lock_init(&zone->lru_lock);
+		zone_seqlock_init(zone);
 		zone->zone_pgdat = pgdat;
 		zone->free_pages = 0;