[PATCH v2] memory hotplug: update the variables after memory removed

[Zhang Zhen <zhenzhang.zhang@huawei.com>]

Commit ea0854170c95245a258b386c7a9314399c949fe0 added a fuction
update_end_of_memory_vars() to update high_memory, max_pfn and
max_low_pfn.

I modified the function according to Dave Hansen and David Rientjes's
suggestions.
And call it in arch_remove_memory() to update these variables too.

Change v1->v2:
- according to Dave Hansen and David Rientjes's suggestions modified
  update_end_of_memory_vars().
Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
---
 arch/x86/mm/init_64.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index df1a992..fd7bd6b 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -673,15 +673,11 @@ void __init paging_init(void)
  * After memory hotplug the variables max_pfn, max_low_pfn and high_memory need
  * updating.
  */
-static void  update_end_of_memory_vars(u64 start, u64 size)
+static void  update_end_of_memory_vars(u64 end_pfn)
 {
-	unsigned long end_pfn = PFN_UP(start + size);
-
-	if (end_pfn > max_pfn) {
-		max_pfn = end_pfn;
-		max_low_pfn = end_pfn;
-		high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
-	}
+	max_pfn = end_pfn;
+	max_low_pfn = end_pfn;
+	high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
 }

 /*
@@ -694,6 +690,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
 	struct zone *zone = pgdat->node_zones + ZONE_NORMAL;
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
+	unsigned long end_pfn;
 	int ret;

 	init_memory_mapping(start, start + size);
@@ -702,7 +699,9 @@ int arch_add_memory(int nid, u64 start, u64 size)
 	WARN_ON_ONCE(ret);

 	/* update max_pfn, max_low_pfn and high_memory */
-	update_end_of_memory_vars(start, size);
+	end_pfn = start_pfn + nr_pages;
+	if (end_pfn > max_pfn)
+		update_end_of_memory_vars(end_pfn);

 	return ret;
 }
@@ -1018,6 +1017,7 @@ int __ref arch_remove_memory(u64 start, u64 size)
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
 	struct zone *zone;
+	unsigned long end_pfn;
 	int ret;

 	zone = page_zone(pfn_to_page(start_pfn));
@@ -1025,6 +1025,11 @@ int __ref arch_remove_memory(u64 start, u64 size)
 	ret = __remove_pages(zone, start_pfn, nr_pages);
 	WARN_ON_ONCE(ret);

+	/* update max_pfn, max_low_pfn and high_memory */
+	end_pfn = start_pfn + nr_pages;
+	if ((max_pfn >= start_pfn) && (max_pfn < end_pfn))
+		update_end_of_memory_vars(start_pfn);
+
 	return ret;
 }
 #endif
-- 
1.8.1.2


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