drivers: base: use standard device online/offline for state change

There are two ways to set the online/offline state for a memory block:
echo 0|1 > online and echo online|online_kernel|online_movable|offline >
state.

The state attribute can online a memory block with extra data, the
"online type", where the online attribute uses a default online type of
ONLINE_KEEP, same as echo online > state.

Currently there is a state_mutex that provides consistency between the
memory block state and the underlying memory.

The problem is that this code does a lot of things that the common
device layer can do for us, such as the serialization of the
online/offline handlers using the device lock, setting the dev->offline
field, and calling kobject_uevent().

This patch refactors the online/offline code to allow the common
device_[online|offline] functions to be used.  The result is a simpler
and more common code path for the two state setting mechanisms.  It also
removes the state_mutex from the struct memory_block as the memory block
device lock provides the state consistency.

No functional change is intended by this patch.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 55 insertions, 72 deletions

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 0187fe483d7c..2a38cd2da2e5 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -16,7 +16,6 @@
 #include <linux/capability.h>
 #include <linux/device.h>
 #include <linux/memory.h>
-#include <linux/kobject.h>
 #include <linux/memory_hotplug.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
@@ -261,9 +260,8 @@ memory_block_action(unsigned long phys_index, unsigned long action, int online_t
         return ret;
 }
 
-static int __memory_block_change_state(struct memory_block *mem,
-                unsigned long to_state, unsigned long from_state_req,
-                int online_type)
+static int memory_block_change_state(struct memory_block *mem,
+                unsigned long to_state, unsigned long from_state_req)
 {
         int ret = 0;
 
@@ -273,105 +271,91 @@ static int __memory_block_change_state(struct memory_block *mem,
         if (to_state == MEM_OFFLINE)
                 mem->state = MEM_GOING_OFFLINE;
 
-        ret = memory_block_action(mem->start_section_nr, to_state, online_type);
+        ret = memory_block_action(mem->start_section_nr, to_state,
+                                mem->online_type);
+
         mem->state = ret ? from_state_req : to_state;
+
         return ret;
 }
 
+/* The device lock serializes operations on memory_subsys_[online|offline] */
 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);
+        if (mem->state == MEM_ONLINE)
+                return 0;
 
-        ret = mem->state == MEM_ONLINE ? 0 :
-                __memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE,
-                                            ONLINE_KEEP);
+        /*
+         * If we are called from store_mem_state(), online_type will be
+         * set >= 0 Otherwise we were called from the device online
+         * attribute and need to set the online_type.
+         */
+        if (mem->online_type < 0)
+                mem->online_type = ONLINE_KEEP;
+
+        ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
+
+        /* clear online_type */
+        mem->online_type = -1;
 
-        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;
-}
+        if (mem->state == MEM_OFFLINE)
+                return 0;
 
-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;
-                }
-        }
-        return ret;
+        return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
 }
 
-static int memory_block_change_state(struct memory_block *mem,
-                unsigned long to_state, unsigned long from_state_req,
-                int online_type)
-{
-        int ret;
-
-        mutex_lock(&mem->state_mutex);
-        ret = __memory_block_change_state_uevent(mem, to_state, from_state_req,
-                                                 online_type);
-        mutex_unlock(&mem->state_mutex);
-
-        return ret;
-}
 static ssize_t
 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;
+        int ret, online_type;
 
         mem = container_of(dev, struct memory_block, dev);
 
         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))) {
-                offline = false;
-                ret = memory_block_change_state(mem, MEM_ONLINE,
-                                                MEM_OFFLINE, ONLINE_MOVABLE);
-        } 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))) {
-                offline = true;
-                ret = memory_block_change_state(mem, MEM_OFFLINE,
-                                                MEM_ONLINE, -1);
+        if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
+                online_type = ONLINE_KERNEL;
+        else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
+                online_type = ONLINE_MOVABLE;
+        else if (!strncmp(buf, "online", min_t(int, count, 6)))
+                online_type = ONLINE_KEEP;
+        else if (!strncmp(buf, "offline", min_t(int, count, 7)))
+                online_type = -1;
+        else
+                return -EINVAL;
+
+        switch (online_type) {
+        case ONLINE_KERNEL:
+        case ONLINE_MOVABLE:
+        case ONLINE_KEEP:
+                /*
+                 * mem->online_type is not protected so there can be a
+                 * race here.  However, when racing online, the first
+                 * will succeed and the second will just return as the
+                 * block will already be online.  The online type
+                 * could be either one, but that is expected.
+                 */
+                mem->online_type = online_type;
+                ret = device_online(&mem->dev);
+                break;
+        case -1:
+                ret = device_offline(&mem->dev);
+                break;
+        default:
+                ret = -EINVAL; /* should never happen */
         }
-        if (!ret)
-                dev->offline = offline;
 
         unlock_device_hotplug();
 
@@ -592,7 +576,6 @@ static int init_memory_block(struct memory_block **memory,
         mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
         mem->state = state;
         mem->section_count++;
-        mutex_init(&mem->state_mutex);
         start_pfn = section_nr_to_pfn(mem->start_section_nr);
         mem->phys_device = arch_get_memory_phys_device(start_pfn);