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>

2 files changed, 28 insertions, 11 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 124324134ff6..46ab2c044b0e 100644
--- a/mm/memory-failure.c
+++ b/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;
 }
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9260314a221e..2c6523af5473 100644
--- a/mm/memory_hotplug.c
+++ b/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 @@ error:
                 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 @@ repeat:
         writeback_set_ratelimit();
 
         memory_notify(MEM_OFFLINE, &arg);
-        unlock_system_sleep();
+        unlock_memory_hotplug();
         return 0;
 
 failed_removal:
@@ -891,7 +908,7 @@ failed_removal:
         undo_isolate_page_range(start_pfn, end_pfn);
 
 out:
-        unlock_system_sleep();
+        unlock_memory_hotplug();
         return ret;
 }