[PATCH 3/8] Add section count to memory_block struct

[Nathan Fontenot <nfont@austin.ibm.com>]

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>

---
 drivers/base/memory.c  |   18 +++++++++++-------
 include/linux/memory.h |    2 ++
 2 files changed, 13 insertions(+), 7 deletions(-)

Index: linux-next/drivers/base/memory.c
===================================================================
--- linux-next.orig/drivers/base/memory.c	2010-09-21 12:36:03.000000000 -0500
+++ linux-next/drivers/base/memory.c	2010-09-21 12:36:45.000000000 -0500
@@ -487,6 +487,7 @@ static int add_memory_block(int nid, str
 
 	mem->start_phys_index = __section_nr(section);
 	mem->state = state;
+	atomic_inc(&mem->section_count);
 	mutex_init(&mem->state_mutex);
 	start_pfn = section_nr_to_pfn(mem->start_phys_index);
 	mem->phys_device = arch_get_memory_phys_device(start_pfn);
@@ -516,13 +517,16 @@ int remove_memory_block(unsigned long no
 	struct memory_block *mem;
 
 	mem = find_memory_block(section);
-	unregister_mem_sect_under_nodes(mem);
-	mem_remove_simple_file(mem, phys_index);
-	mem_remove_simple_file(mem, end_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);
+
+	if (atomic_dec_and_test(&mem->section_count)) {
+		unregister_mem_sect_under_nodes(mem);
+		mem_remove_simple_file(mem, phys_index);
+		mem_remove_simple_file(mem, end_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);
+	}
 
 	return 0;
 }
Index: linux-next/include/linux/memory.h
===================================================================
--- linux-next.orig/include/linux/memory.h	2010-09-21 12:34:04.000000000 -0500
+++ linux-next/include/linux/memory.h	2010-09-21 12:36:45.000000000 -0500
@@ -19,11 +19,13 @@
 #include <linux/node.h>
 #include <linux/compiler.h>
 #include <linux/mutex.h>
+#include <asm/atomic.h>
 
 struct memory_block {
 	unsigned long start_phys_index;
 	unsigned long end_phys_index;
 	unsigned long state;
+	atomic_t section_count;
 	/*
 	 * This serializes all state change requests.  It isn't
 	 * held during creation because the control files are