From: Chris Lalancette <clalance@redhat.com>
Date: Thu, 5 Mar 2009 14:13:05 +0100
Subject: [xen] xen reports bogus LowTotal
Message-id: 49AFCFE1.9050501@redhat.com
O-Subject: [RHEL5.4 PATCH]: Xen reports bogus LowTotal
Bugzilla: 428892
RH-Acked-by: Don Dutile <ddutile@redhat.com>
RH-Acked-by: Rik van Riel <riel@redhat.com>

All,
     The xen kernel can report a LowTotal of 4Tb on a system, even though the
system only has 3.5Gb of memory.  That's obviously totally bogus.  The problem
is that the balloon driver wasn't properly accounting for totalhigh_pages in
it's calculations, which screws up the rest of the reporting in the system.
This is a straightforward backport of linux-2.6.18-xen.hg c/s 79 and 128, and
seems to fix the problem for the reporter.
      This will fix BZ 428892.  Please review and ACK

--
Chris Lalancette

diff --git a/drivers/xen/balloon/balloon.c b/drivers/xen/balloon/balloon.c
index 39d7185..e8ce44f 100644
--- a/drivers/xen/balloon/balloon.c
+++ b/drivers/xen/balloon/balloon.c
@@ -93,6 +93,15 @@ static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
 /* VM /proc information for memory */
 extern unsigned long totalram_pages;
 
+#ifndef MODULE
+extern unsigned long totalhigh_pages;
+#define inc_totalhigh_pages() (totalhigh_pages++)
+#define dec_totalhigh_pages() (totalhigh_pages--)
+#else
+#define inc_totalhigh_pages() ((void)0)
+#define dec_totalhigh_pages() ((void)0)
+#endif
+
 /* We may hit the hard limit in Xen. If we do then we remember it. */
 static unsigned long hard_limit;
 
@@ -137,6 +146,7 @@ static void balloon_append(struct page *page)
 	if (PageHighMem(page)) {
 		list_add_tail(PAGE_TO_LIST(page), &ballooned_pages);
 		balloon_high++;
+		dec_totalhigh_pages();
 	} else {
 		list_add(PAGE_TO_LIST(page), &ballooned_pages);
 		balloon_low++;
@@ -154,8 +164,10 @@ static struct page *balloon_retrieve(void)
 	page = LIST_TO_PAGE(ballooned_pages.next);
 	UNLIST_PAGE(page);
 
-	if (PageHighMem(page))
+	if (PageHighMem(page)) {
 		balloon_high--;
+		inc_totalhigh_pages();
+	}
 	else
 		balloon_low--;