[RFC PATCH v3 4/13] memory-hotplug : remove /sys/firmware/memmap/X sysfs

[Yasuaki Ishimatsu]

When (hot)adding memory into system, /sys/firmware/memmap/X/{end, start, type}
sysfs files are created. But there is no code to remove these files. The patch
implements the function to remove them.

Note : The code does not free firmware_map_entry since there is no way to free
       memory which is allocated by bootmem.

CC: David Rientjes <rientjes at google.com>
CC: Jiang Liu <liuj97 at gmail.com>
CC: Len Brown <len.brown at intel.com>
CC: Benjamin Herrenschmidt <benh at kernel.crashing.org>
CC: Paul Mackerras <paulus at samba.org>
CC: Christoph Lameter <cl at linux.com>
Cc: Minchan Kim <minchan.kim at gmail.com>
CC: Andrew Morton <akpm at linux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
CC: Wen Congyang <wency at cn.fujitsu.com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki at jp.fujitsu.com>

---
 drivers/firmware/memmap.c    |   78 ++++++++++++++++++++++++++++++++++++++++++-
 include/linux/firmware-map.h |    6 +++
 mm/memory_hotplug.c          |    6 ++-
 3 files changed, 88 insertions(+), 2 deletions(-)

Index: linux-3.5-rc6/mm/memory_hotplug.c
===================================================================
--- linux-3.5-rc6.orig/mm/memory_hotplug.c	2012-07-09 18:23:13.323844923 +0900
+++ linux-3.5-rc6/mm/memory_hotplug.c	2012-07-09 18:23:19.522767424 +0900
@@ -661,7 +661,11 @@ EXPORT_SYMBOL_GPL(add_memory);

 int remove_memory(int nid, u64 start, u64 size)
 {
-	return -EBUSY;
+	lock_memory_hotplug();
+	/* remove memmap entry */
+	firmware_map_remove(start, start + size - 1, "System RAM");
+	unlock_memory_hotplug();
+	return 0;

 }
 EXPORT_SYMBOL_GPL(remove_memory);
Index: linux-3.5-rc6/include/linux/firmware-map.h
===================================================================
--- linux-3.5-rc6.orig/include/linux/firmware-map.h	2012-07-09 18:23:09.532892314 +0900
+++ linux-3.5-rc6/include/linux/firmware-map.h	2012-07-09 18:23:19.523767412 +0900
@@ -25,6 +25,7 @@

 int firmware_map_add_early(u64 start, u64 end, const char *type);
 int firmware_map_add_hotplug(u64 start, u64 end, const char *type);
+int firmware_map_remove(u64 start, u64 end, const char *type);

 #else /* CONFIG_FIRMWARE_MEMMAP */

@@ -38,6 +39,11 @@ static inline int firmware_map_add_hotpl
 	return 0;
 }

+static inline int firmware_map_remove(u64 start, u64 end, const char *type)
+{
+	return 0;
+}
+
 #endif /* CONFIG_FIRMWARE_MEMMAP */

 #endif /* _LINUX_FIRMWARE_MAP_H */
Index: linux-3.5-rc6/drivers/firmware/memmap.c
===================================================================
--- linux-3.5-rc6.orig/drivers/firmware/memmap.c	2012-07-09 18:23:09.532892314 +0900
+++ linux-3.5-rc6/drivers/firmware/memmap.c	2012-07-09 18:25:46.371931554 +0900
@@ -21,6 +21,7 @@
 #include <linux/types.h>
 #include <linux/bootmem.h>
 #include <linux/slab.h>
+#include <linux/mm.h>

 /*
  * Data types ------------------------------------------------------------------
@@ -79,7 +80,22 @@ static const struct sysfs_ops memmap_att
 	.show = memmap_attr_show,
 };

+#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
+
+static void release_firmware_map_entry(struct kobject *kobj)
+{
+	struct firmware_map_entry *entry = to_memmap_entry(kobj);
+	struct page *head_page;
+
+	head_page = virt_to_head_page(entry);
+	if (PageSlab(head_page))
+		kfree(entry);
+
+	/* There is no way to free memory allocated from bootmem*/
+}
+
 static struct kobj_type memmap_ktype = {
+	.release	= release_firmware_map_entry,
 	.sysfs_ops	= &memmap_attr_ops,
 	.default_attrs	= def_attrs,
 };
@@ -123,6 +139,16 @@ static int firmware_map_add_entry(u64 st
 	return 0;
 }

+/**
+ * firmware_map_remove_entry() - Does the real work to remove a firmware
+ * memmap entry.
+ * @entry: removed entry.
+ **/
+static inline void firmware_map_remove_entry(struct firmware_map_entry *entry)
+{
+	list_del(&entry->list);
+}
+
 /*
  * Add memmap entry on sysfs
  */
@@ -144,6 +170,31 @@ static int add_sysfs_fw_map_entry(struct
 	return 0;
 }

+/*
+ * Remove memmap entry on sysfs
+ */
+static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry)
+{
+	kobject_put(&entry->kobj);
+}
+
+/*
+ * Search memmap entry
+ */
+
+struct firmware_map_entry * __meminit
+find_firmware_map_entry(u64 start, u64 end, const char *type)
+{
+	struct firmware_map_entry *entry;
+
+	list_for_each_entry(entry, &map_entries, list)
+		if ((entry->start == start) && (entry->end == end) &&
+		    (!strcmp(entry->type, type)))
+			return entry;
+
+	return NULL;
+}
+
 /**
  * firmware_map_add_hotplug() - Adds a firmware mapping entry when we do
  * memory hotplug.
@@ -196,6 +247,32 @@ int __init firmware_map_add_early(u64 st
 	return firmware_map_add_entry(start, end, type, entry);
 }

+/**
+ * firmware_map_remove() - remove a firmware mapping entry
+ * @start: Start of the memory range.
+ * @end:   End of the memory range (inclusive).
+ * @type:  Type of the memory range.
+ *
+ * removes a firmware mapping entry.
+ *
+ * Returns 0 on success, or -EINVAL if no entry.
+ **/
+int __meminit firmware_map_remove(u64 start, u64 end, const char *type)
+{
+	struct firmware_map_entry *entry;
+
+	entry = find_firmware_map_entry(start, end, type);
+	if (!entry)
+		return -EINVAL;
+
+	/* remove the memmap entry */
+	remove_sysfs_fw_map_entry(entry);
+
+	firmware_map_remove_entry(entry);
+
+	return 0;
+}
+
 /*
  * Sysfs functions -------------------------------------------------------------
  */
@@ -218,7 +295,6 @@ static ssize_t type_show(struct firmware
 }

 #define to_memmap_attr(_attr) container_of(_attr, struct memmap_attribute, attr)
-#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)

 static ssize_t memmap_attr_show(struct kobject *kobj,
 				struct attribute *attr, char *buf)