Driver core: Introduce offline/online callbacks for memory blocks

Introduce .offline() and .online() callbacks for memory_subsys
that will allow the generic device_offline() and device_online()
to be used with device objects representing memory blocks.  That,
in turn, allows the ACPI subsystem to use device_offline() to put
removable memory blocks offline, if possible, before removing
memory modules holding them.

The 'online' sysfs attribute of memory block devices will attempt to
put them offline if 0 is written to it and will attempt to apply the
previously used online type when onlining them (i.e. when 1 is
written to it).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Toshi Kani <toshi.kani@hp.com>

drivers/base/memory.c

@@ -37,9 +37,14 @@ static inline int base_memory_block_id(int section_nr)
 	return section_nr / sections_per_block;
 }
 
+static int memory_subsys_online(struct device *dev);
+static int memory_subsys_offline(struct device *dev);
+
 static struct bus_type memory_subsys = {
 	.name = MEMORY_CLASS_NAME,
 	.dev_name = MEMORY_CLASS_NAME,
+	.online = memory_subsys_online,
+	.offline = memory_subsys_offline,
 };
 
 static BLOCKING_NOTIFIER_HEAD(memory_chain);
@@ -88,6 +93,7 @@ int register_memory(struct memory_block *memory)
 	memory->dev.bus = &memory_subsys;
 	memory->dev.id = memory->start_section_nr / sections_per_block;
 	memory->dev.release = memory_block_release;
+	memory->dev.offline = memory->state == MEM_OFFLINE;
 
 	error = device_register(&memory->dev);
 	return error;
@@ -278,33 +284,70 @@ static int __memory_block_change_state(struct memory_block *mem,
 {
 	int ret = 0;
 
-	if (mem->state != from_state_req) {
-		ret = -EINVAL;
-		goto out;
-	}
+	if (mem->state != from_state_req)
+		return -EINVAL;
 
 	if (to_state == MEM_OFFLINE)
 		mem->state = MEM_GOING_OFFLINE;
 
 	ret = memory_block_action(mem->start_section_nr, to_state, online_type);
-
 	if (ret) {
 		mem->state = from_state_req;
-		goto out;
+	} else {
+		mem->state = to_state;
+		if (to_state == MEM_ONLINE)
+			mem->last_online = online_type;
 	}
+	return ret;
+}
 
-	mem->state = to_state;
-	switch (mem->state) {
-	case MEM_OFFLINE:
-		kobject_uevent(&mem->dev.kobj, KOBJ_OFFLINE);
-		break;
-	case MEM_ONLINE:
-		kobject_uevent(&mem->dev.kobj, KOBJ_ONLINE);
-		break;
-	default:
-		break;
+static int memory_subsys_online(struct device *dev)
+{
+	struct memory_block *mem = container_of(dev, struct memory_block, dev);
+	int ret;
+
+	mutex_lock(&mem->state_mutex);
+
+	ret = mem->state == MEM_ONLINE ? 0 :
+		__memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE,
+					    mem->last_online);
+
+	mutex_unlock(&mem->state_mutex);
+	return ret;
+}
+
+static int memory_subsys_offline(struct device *dev)
+{
+	struct memory_block *mem = container_of(dev, struct memory_block, dev);
+	int ret;
+
+	mutex_lock(&mem->state_mutex);
+
+	ret = mem->state == MEM_OFFLINE ? 0 :
+		__memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1);
+
+	mutex_unlock(&mem->state_mutex);
+	return ret;
+}
+
+static int __memory_block_change_state_uevent(struct memory_block *mem,
+		unsigned long to_state, unsigned long from_state_req,
+		int online_type)
+{
+	int ret = __memory_block_change_state(mem, to_state, from_state_req,
+					      online_type);
+	if (!ret) {
+		switch (mem->state) {
+		case MEM_OFFLINE:
+			kobject_uevent(&mem->dev.kobj, KOBJ_OFFLINE);
+			break;
+		case MEM_ONLINE:
+			kobject_uevent(&mem->dev.kobj, KOBJ_ONLINE);
+			break;
+		default:
+			break;
+		}
 	}
-out:
 	return ret;
 }
 
@@ -315,8 +358,8 @@ static int memory_block_change_state(struct memory_block *mem,
 	int ret;
 
 	mutex_lock(&mem->state_mutex);
-	ret = __memory_block_change_state(mem, to_state, from_state_req,
-					  online_type);
+	ret = __memory_block_change_state_uevent(mem, to_state, from_state_req,
+						 online_type);
 	mutex_unlock(&mem->state_mutex);
 
 	return ret;
@@ -326,22 +369,34 @@ store_mem_state(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
 	struct memory_block *mem;
+	bool offline;
 	int ret = -EINVAL;
 
 	mem = container_of(dev, struct memory_block, dev);
 
-	if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
+	lock_device_hotplug();
+
+	if (!strncmp(buf, "online_kernel", min_t(int, count, 13))) {
+		offline = false;
 		ret = memory_block_change_state(mem, MEM_ONLINE,
 						MEM_OFFLINE, ONLINE_KERNEL);
-	else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
+	} else if (!strncmp(buf, "online_movable", min_t(int, count, 14))) {
+		offline = false;
 		ret = memory_block_change_state(mem, MEM_ONLINE,
 						MEM_OFFLINE, ONLINE_MOVABLE);
-	else if (!strncmp(buf, "online", min_t(int, count, 6)))
+	} else if (!strncmp(buf, "online", min_t(int, count, 6))) {
+		offline = false;
 		ret = memory_block_change_state(mem, MEM_ONLINE,
 						MEM_OFFLINE, ONLINE_KEEP);
-	else if(!strncmp(buf, "offline", min_t(int, count, 7)))
+	} else if(!strncmp(buf, "offline", min_t(int, count, 7))) {
+		offline = true;
 		ret = memory_block_change_state(mem, MEM_OFFLINE,
 						MEM_ONLINE, -1);
+	}
+	if (!ret)
+		dev->offline = offline;
+
+	unlock_device_hotplug();
 
 	if (ret)
 		return ret;
@@ -563,6 +618,7 @@ static int init_memory_block(struct memory_block **memory,
 			base_memory_block_id(scn_nr) * sections_per_block;
 	mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
 	mem->state = state;
+	mem->last_online = ONLINE_KEEP;
 	mem->section_count++;
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->start_section_nr);
@@ -681,14 +737,20 @@ int unregister_memory_section(struct mem_section *section)
 
 /*
  * offline one memory block. If the memory block has been offlined, do nothing.
+ *
+ * Call under device_hotplug_lock.
  */
 int offline_memory_block(struct memory_block *mem)
 {
 	int ret = 0;
 
 	mutex_lock(&mem->state_mutex);
-	if (mem->state != MEM_OFFLINE)
-		ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1);
+	if (mem->state != MEM_OFFLINE) {
+		ret = __memory_block_change_state_uevent(mem, MEM_OFFLINE,
+							 MEM_ONLINE, -1);
+		if (!ret)
+			mem->dev.offline = true;
+	}
 	mutex_unlock(&mem->state_mutex);
 
 	return ret;

include/linux/memory.h

@@ -26,6 +26,7 @@ struct memory_block {
 	unsigned long start_section_nr;
 	unsigned long end_section_nr;
 	unsigned long state;
+	int last_online;
 	int section_count;
 
 	/*