From: Dave Hansen <haveblue@us.ibm.com>
Date: Sun, 30 Oct 2005 01:16:52 +0000 (-0700)
Subject: [PATCH] memory hotplug prep: fixup bad_range()
X-Git-Tag: v2.6.15-rc1~730^2^2~12
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c6a57e19e464db118dc4ab9cfe9e9748c6d630a0;p=linux-2.6

[PATCH] memory hotplug prep: fixup bad_range()

When doing memory hotplug operations, the size of existing zones can obviously
change.  This means that zone->zone_{start_pfn,spanned_pages} can change.

There are currently no locks that protect these structure members.  However,
they are rarely accessed at runtime.  Outside of swsusp, the only place that I
can find is bad_range().

So, split bad_range() up into two pieces: one that needs to be locked and
anther that doesn't.

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>
---

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9a2fa8110a..a51ef94eec 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -78,21 +78,37 @@ int min_free_kbytes = 1024;
 unsigned long __initdata nr_kernel_pages;
 unsigned long __initdata nr_all_pages;
 
-/*
- * Temporary debugging check for pages not lying within a given zone.
- */
-static int bad_range(struct zone *zone, struct page *page)
+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;
+
+	return 0;
+}
+
+static int page_is_consistent(struct zone *zone, struct page *page)
+{
 #ifdef CONFIG_HOLES_IN_ZONE
 	if (!pfn_valid(page_to_pfn(page)))
-		return 1;
+		return 0;
 #endif
 	if (zone != page_zone(page))
+		return 0;
+
+	return 1;
+}
+/*
+ * Temporary debugging check for pages not lying within a given zone.
+ */
+static int bad_range(struct zone *zone, struct page *page)
+{
+	if (page_outside_zone_boundaries(zone, page))
 		return 1;
+	if (!page_is_consistent(zone, page))
+		return 1;
+
 	return 0;
 }