memory hotplug: update the variables after memory removed

PATCH Superseded Zhang Zhen 1 participant 2 messages Jul 29, 2014 1 message not in the archive

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Memory management x86 x86 MM

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Zhang Zhen

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2014-07-29 11:35 UTC #1 lore raw

PATCH v3 1/1 memory hotplug: update the variables after memory removed

Commit ea0854170c95 ("memory hotplug: fix a bug on /dev/mem for 64-bit kernels") added a fuction update_end_of_memory_vars() to update high_memory, max_pfn and max_low_pfn.

Here we may access wrong memory via /dev/mem after memory remove without this patch.
I modified the function 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().
change v2->v3:
- remove the extra space before the function identifier of update_end_of_memory_vars().
- remove the end_pfn and use start_pfn + nr_pages in the conditional.

Signed-off-by Zhang Zhen <[email protected]>

---
 arch/x86/mm/init_64.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

arch/x86/mm/init_64.c +12 -9

index df1a992..d16368e 100644
@@ -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;
 }

@@ -1025,6 +1024,10 @@ 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 */
+	if ((max_pfn >= start_pfn) && (max_pfn < (start_pfn + nr_pages)))
+		update_end_of_memory_vars(start_pfn);
+
 	return ret;
 }
 #endif

Signature · 4 lines

1.8.1.2


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