linux-kernel - [PATCH] hibernate / memory hotplug: always use for_each_populated

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Message-Id: <1248103551.23961.0.camel@localhost.localdomain>
Date:	Mon, 20 Jul 2009 17:25:51 +0200
From:	Gerald Schaefer <gerald.schaefer@...ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Yasunori Goto <y-goto@...fujitsu.com>
Subject: [PATCH] hibernate / memory hotplug: always use
	for_each_populated_zone()

From: Gerald Schaefer <gerald.schaefer@...ibm.com>

Use for_each_populated_zone() instead of for_each_zone() in hibernation
code. This fixes a bug on s390, where we allow both config options
HIBERNATION and MEMORY_HOTPLUG, so that we also have a ZONE_MOVABLE
here. We only allow hibernation if no memory hotplug operation was
performed, so in fact both features can only be used exclusively, but
this way we don't need 2 differently configured (distribution) kernels.

If we have an unpopulated ZONE_MOVABLE, we allow hibernation but run
into a BUG_ON() in memory_bm_test/set/clear_bit() because hibernation
code iterates through all zones, not only the populated zones, in
several places. For example, swsusp_free() does for_each_zone() and
then checks for pfn_valid(), which is true even if the zone is not
populated, resulting in a BUG_ON() later because the pfn cannot be
found in the memory bitmap.

Replacing all occurences of for_each_zone() in hibernation code with
for_each_populated_zone() would fix this issue.

Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>
---
 kernel/power/snapshot.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Index: linux-2.6-work/kernel/power/snapshot.c
===================================================================
--- linux-2.6-work.orig/kernel/power/snapshot.c
+++ linux-2.6-work/kernel/power/snapshot.c
@@ -853,7 +853,7 @@ static unsigned int count_highmem_pages(
 	struct zone *zone;
 	unsigned int n = 0;
 
-	for_each_zone(zone) {
+	for_each_populated_zone(zone) {
 		unsigned long pfn, max_zone_pfn;
 
 		if (!is_highmem(zone))
@@ -916,7 +916,7 @@ static unsigned int count_data_pages(voi
 	unsigned long pfn, max_zone_pfn;
 	unsigned int n = 0;
 
-	for_each_zone(zone) {
+	for_each_populated_zone(zone) {
 		if (is_highmem(zone))
 			continue;
 
@@ -1010,7 +1010,7 @@ copy_data_pages(struct memory_bitmap *co
 	struct zone *zone;
 	unsigned long pfn;
 
-	for_each_zone(zone) {
+	for_each_populated_zone(zone) {
 		unsigned long max_zone_pfn;
 
 		mark_free_pages(zone);
@@ -1046,7 +1046,7 @@ void swsusp_free(void)
 	struct zone *zone;
 	unsigned long pfn, max_zone_pfn;
 
-	for_each_zone(zone) {
+	for_each_populated_zone(zone) {
 		max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
 			if (pfn_valid(pfn)) {
@@ -1166,7 +1166,7 @@ static int enough_free_mem(unsigned int 
 	struct zone *zone;
 	unsigned int free = 0, meta = 0;
 
-	for_each_zone(zone) {
+	for_each_populated_zone(zone) {
 		meta += snapshot_additional_pages(zone);
 		if (!is_highmem(zone))
 			free += zone_page_state(zone, NR_FREE_PAGES);
@@ -1474,7 +1474,7 @@ static int mark_unsafe_pages(struct memo
 	unsigned long pfn, max_zone_pfn;
 
 	/* Clear page flags */
-	for_each_zone(zone) {
+	for_each_populated_zone(zone) {
 		max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
 			if (pfn_valid(pfn))

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