linux-kernel - [PATCH 1/2] memory-hotplug: fix not enough check of valid zones

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Date:	Wed, 27 Aug 2014 19:16:00 +0800
From:	Zhang Zhen <zhenzhang.zhang@...wei.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>
CC:	<wangnan0@...wei.com>, Linux MM <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] memory-hotplug: fix not enough check of valid zones

As Yasuaki Ishimatsu described the check here is not enough
if memory has hole as follows:

PFN       0x00          0xd0          0xe0          0xf0
             +-------------+-------------+-------------+
zone type   |   Normal    |     hole    |   Normal    |
             +-------------+-------------+-------------+
In this case, the check can't guarantee that this is "the last
block of memory".
The check of ZONE_MOVABLE has the same problem.

Signed-off-by: Zhang Zhen <zhenzhang.zhang@...wei.com>
---
 drivers/base/memory.c | 36 ++++++------------------------------
 1 file changed, 6 insertions(+), 30 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index ccaf37c..0fc1d25 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -374,20 +374,6 @@ static ssize_t show_phys_device(struct device *dev,
 }

 #ifdef CONFIG_MEMORY_HOTREMOVE
-static int __zones_online_to(unsigned long end_pfn,
-				struct page *first_page, unsigned long nr_pages)
-{
-	struct zone *zone_next;
-
-	/* The mem block is the last block of memory. */
-	if (!pfn_valid(end_pfn + 1))
-		return 1;
-	zone_next = page_zone(first_page + nr_pages);
-	if (zone_idx(zone_next) == ZONE_MOVABLE)
-		return 1;
-	return 0;
-}
-
 static ssize_t show_zones_online_to(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
@@ -407,28 +393,18 @@ static ssize_t show_zones_online_to(struct device *dev,

 	zone = page_zone(first_page);

-#ifdef CONFIG_HIGHMEM
-	if (zone_idx(zone) == ZONE_HIGHMEM) {
-		if (__zones_online_to(end_pfn, first_page, nr_pages))
+	if (zone_idx(zone) == ZONE_MOVABLE - 1) {
+		/*The mem block is the last memoryblock of this zone.*/
+		if (end_pfn == zone_end_pfn(zone))
 			return sprintf(buf, "%s %s\n",
 					zone->name, (zone + 1)->name);
 	}
-#else
-	if (zone_idx(zone) == ZONE_NORMAL) {
-		if (__zones_online_to(end_pfn, first_page, nr_pages))
-			return sprintf(buf, "%s %s\n",
-					zone->name, (zone + 1)->name);
-	}
-#endif

 	if (zone_idx(zone) == ZONE_MOVABLE) {
-		if (!pfn_valid(start_pfn - nr_pages))
-			return sprintf(buf, "%s %s\n",
-						zone->name, (zone - 1)->name);
-		zone_prev = page_zone(first_page - nr_pages);
-		if (zone_idx(zone_prev) != ZONE_MOVABLE)
+		/*The mem block is the first memoryblock of ZONE_MOVABLE.*/
+		if (start_pfn == zone->zone_start_pfn)
 			return sprintf(buf, "%s %s\n",
-						zone->name, (zone - 1)->name);
+					zone->name, (zone - 1)->name);
 	}

 	return sprintf(buf, "%s\n", zone->name);
-- 
1.8.1.4


.




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