mem-hotplug: introduce {un}lock_memory_hotplug()

Presently hwpoison is using lock_system_sleep() to prevent a race with
memory hotplug.  However lock_system_sleep() is a no-op if
CONFIG_HIBERNATION=n.  Therefore we need a new lock.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memory_hotplug.h

@@ -161,6 +161,9 @@ extern void register_page_bootmem_info_node(struct pglist_data *pgdat);
 extern void put_page_bootmem(struct page *page);
 #endif
 
+void lock_memory_hotplug(void);
+void unlock_memory_hotplug(void);
+
 #else /* ! CONFIG_MEMORY_HOTPLUG */
 /*
  * Stub functions for when hotplug is off
@@ -192,6 +195,9 @@ static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
 {
 }
 
+static inline void lock_memory_hotplug(void) {}
+static inline void unlock_memory_hotplug(void) {}
+
 #endif /* ! CONFIG_MEMORY_HOTPLUG */
 
 #ifdef CONFIG_MEMORY_HOTREMOVE

mm/memory-failure.c

@@ -51,6 +51,7 @@
 #include <linux/slab.h>
 #include <linux/swapops.h>
 #include <linux/hugetlb.h>
+#include <linux/memory_hotplug.h>
 #include "internal.h"
 
 int sysctl_memory_failure_early_kill __read_mostly = 0;
@@ -1230,11 +1231,10 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
 		return 1;
 
 	/*
-	 * The lock_system_sleep prevents a race with memory hotplug,
-	 * because the isolation assumes there's only a single user.
+	 * The lock_memory_hotplug prevents a race with memory hotplug.
 	 * This is a big hammer, a better would be nicer.
 	 */
-	lock_system_sleep();
+	lock_memory_hotplug();
 
 	/*
 	 * Isolate the page, so that it doesn't get reallocated if it
@@ -1264,7 +1264,7 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
 		ret = 1;
 	}
 	unset_migratetype_isolate(p);
-	unlock_system_sleep();
+	unlock_memory_hotplug();
 	return ret;
 }
 

mm/memory_hotplug.c

@@ -34,6 +34,23 @@
 
 #include "internal.h"
 
+DEFINE_MUTEX(mem_hotplug_mutex);
+
+void lock_memory_hotplug(void)
+{
+	mutex_lock(&mem_hotplug_mutex);
+
+	/* for exclusive hibernation if CONFIG_HIBERNATION=y */
+	lock_system_sleep();
+}
+
+void unlock_memory_hotplug(void)
+{
+	unlock_system_sleep();
+	mutex_unlock(&mem_hotplug_mutex);
+}
+
+
 /* add this memory to iomem resource */
 static struct resource *register_memory_resource(u64 start, u64 size)
 {
@@ -493,7 +510,7 @@ int mem_online_node(int nid)
 	pg_data_t	*pgdat;
 	int	ret;
 
-	lock_system_sleep();
+	lock_memory_hotplug();
 	pgdat = hotadd_new_pgdat(nid, 0);
 	if (pgdat) {
 		ret = -ENOMEM;
@@ -504,7 +521,7 @@ int mem_online_node(int nid)
 	BUG_ON(ret);
 
 out:
-	unlock_system_sleep();
+	unlock_memory_hotplug();
 	return ret;
 }
 
@@ -516,7 +533,7 @@ int __ref add_memory(int nid, u64 start, u64 size)
 	struct resource *res;
 	int ret;
 
-	lock_system_sleep();
+	lock_memory_hotplug();
 
 	res = register_memory_resource(start, size);
 	ret = -EEXIST;
@@ -563,7 +580,7 @@ int __ref add_memory(int nid, u64 start, u64 size)
 		release_memory_resource(res);
 
 out:
-	unlock_system_sleep();
+	unlock_memory_hotplug();
 	return ret;
 }
 EXPORT_SYMBOL_GPL(add_memory);
@@ -791,7 +808,7 @@ static int offline_pages(unsigned long start_pfn,
 	if (!test_pages_in_a_zone(start_pfn, end_pfn))
 		return -EINVAL;
 
-	lock_system_sleep();
+	lock_memory_hotplug();
 
 	zone = page_zone(pfn_to_page(start_pfn));
 	node = zone_to_nid(zone);
@@ -880,7 +897,7 @@ static int offline_pages(unsigned long start_pfn,
 	writeback_set_ratelimit();
 
 	memory_notify(MEM_OFFLINE, &arg);
-	unlock_system_sleep();
+	unlock_memory_hotplug();
 	return 0;
 
 failed_removal:
@@ -891,7 +908,7 @@ static int offline_pages(unsigned long start_pfn,
 	undo_isolate_page_range(start_pfn, end_pfn);
 
 out:
-	unlock_system_sleep();
+	unlock_memory_hotplug();
 	return ret;
 }