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>

1 files changed, 87 insertions, 25 deletions

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 14f8a6954da0..c8f3b63fcacd 100644
--- a/drivers/base/memory.c
+++ b/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;