Driver core: Add section count to memory_block struct

Add a section count property to the memory_block struct to track the number
of memory sections that have been added/removed from a memory block. This
allows us to know when the last memory section of a memory block has been
removed so we can remove the memory block.
Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
Reviewed-by: Robin Holt <holt@sgi.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/memory.c

@@ -490,6 +490,7 @@ static int add_memory_block(int nid, struct mem_section *section,
 
 	mem->phys_index = __section_nr(section);
 	mem->state = state;
+	mem->section_count++;
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->phys_index);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);
@@ -519,12 +520,16 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
 
 	mutex_lock(&mem_sysfs_mutex);
 	mem = find_memory_block(section);
+
+	mem->section_count--;
+	if (mem->section_count == 0) {
 		unregister_mem_sect_under_nodes(mem);
 		mem_remove_simple_file(mem, phys_index);
 		mem_remove_simple_file(mem, state);
 		mem_remove_simple_file(mem, phys_device);
 		mem_remove_simple_file(mem, removable);
 		unregister_memory(mem, section);
+	}
 
 	mutex_unlock(&mem_sysfs_mutex);
 	return 0;

include/linux/memory.h

@@ -23,6 +23,8 @@
 struct memory_block {
 	unsigned long phys_index;
 	unsigned long state;
+	int section_count;
+
 	/*
 	 * This serializes all state change requests.  It isn't
 	 * held during creation because the control files are