Re: [RFC PATCH v4 4/13] memory-hotplug : remove /sys/firmware/memmap/X sysfs

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@google.com>
CC: Jiang Liu <redacted>
CC: Len Brown <redacted>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <redacted> 
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted> 
CC: Wen Congyang <redacted>
Signed-off-by: Yasuaki Ishimatsu <redacted>

---
 drivers/firmware/memmap.c    |   78 ++++++++++++++++++++++++++++++++++++++++++-
 include/linux/firmware-map.h |    6 +++
 mm/memory_hotplug.c          |    9 +++-
 3 files changed, 90 insertions(+), 3 deletions(-)

Index: linux-3.5-rc6/mm/memory_hotplug.c
===================================================================

--- linux-3.5-rc6.orig/mm/memory_hotplug.c	2012-07-18 17:20:05.670024283 +0900
+++ linux-3.5-rc6/mm/memory_hotplug.c	2012-07-18 17:51:03.933189930 +0900

@@ -1012,9 +1012,9 @@ int offline_memory(u64 start, u64 size)
 	return offline_pages(start_pfn, end_pfn, 120 * HZ);
 }
 
-int remove_memory(int nid, u64 start, u64 size)
+int __ref remove_memory(int nid, u64 start, u64 size)
 {
-	int ret = -EBUSY;
+	int ret = 0;
 	lock_memory_hotplug();
 	/*
 	 * The memory might become online by other task, even if you offine it.

@@ -1025,8 +1025,13 @@ int remove_memory(int nid, u64 start, u6
 			"because the memmory range is online\n",
 			start, start + size);
 		ret = -EAGAIN;
+		goto out;
 	}
 
+	/* remove memmap entry */
+	firmware_map_remove(start, start + size, "System RAM");
+
+out:
 	unlock_memory_hotplug();
 	return ret;
 

Index: linux-3.5-rc6/include/linux/firmware-map.h
===================================================================

--- linux-3.5-rc6.orig/include/linux/firmware-map.h	2012-07-18 17:19:37.007382563 +0900
+++ linux-3.5-rc6/include/linux/firmware-map.h	2012-07-18 17:42:20.804730245 +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	2012-07-18 17:19:43.618300182 +0900
+++ linux-3.5-rc6/drivers/firmware/memmap.c	2012-07-18 17:42:20.846729721 +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 *page;
+
+	page = virt_to_page(entry);
+	if (PageSlab(page) || PageCompound(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.
+ * @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 - 1, type);
+	if (!entry)
+		return -EINVAL;
+
+	firmware_map_remove_entry(entry);
+
+	/* remove the memmap entry */
+	remove_sysfs_fw_map_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)

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