[Patch 005/005](memory hotplug) free memmaps allocated by bootmem

[Yasunori Goto <y-goto@jp.fujitsu.com>]

This patch is to free memmaps which is allocated by bootmem.

Freeing usemap is not necessary. The pages of usemap may be necessary
for other sections.

If removing section is last section on the node,
its section is the final user of usemap page.
(usemaps are allocated on its section by previous patch.)
But it shouldn't be freed too, because the section must be
logical offline state which all pages are isolated against page allocater.
If it is freed, page alloctor may use it which will be removed
physically soon. It will be disaster.
So, this patch keeps it as it is.


Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>

---
 mm/internal.h       |    3 +--
 mm/memory_hotplug.c |   11 +++++++++++
 mm/page_alloc.c     |    2 +-
 mm/sparse.c         |   51 +++++++++++++++++++++++++++++++++++++++++++++++----
 4 files changed, 60 insertions(+), 7 deletions(-)

Index: current/mm/sparse.c
===================================================================
--- current.orig/mm/sparse.c	2008-04-07 20:13:25.000000000 +0900
+++ current/mm/sparse.c	2008-04-07 20:27:20.000000000 +0900
@@ -8,6 +8,7 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
+#include "internal.h"
 #include <asm/dma.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
@@ -360,6 +361,9 @@
 {
 	return; /* XXX: Not implemented yet */
 }
+static void free_map_bootmem(struct page *page, unsigned long nr_pages)
+{
+}
 #else
 static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
 {
@@ -397,17 +401,47 @@
 		free_pages((unsigned long)memmap,
 			   get_order(sizeof(struct page) * nr_pages));
 }
+
+static void free_map_bootmem(struct page *page, unsigned long nr_pages)
+{
+	unsigned long maps_section_nr, removing_section_nr, i;
+	int magic;
+
+	for (i = 0; i < nr_pages; i++, page++) {
+		magic = atomic_read(&page->_mapcount);
+
+		BUG_ON(magic == NODE_INFO);
+
+		maps_section_nr = pfn_to_section_nr(page_to_pfn(page));
+		removing_section_nr = page->private;
+
+		/*
+		 * When this function is called, the removing section is
+		 * logical offlined state. This means all pages are isolated
+		 * from page allocator. If removing section's memmap is placed
+		 * on the same section, it must not be freed.
+		 * If it is freed, page allocator may allocate it which will
+		 * be removed physically soon.
+		 */
+		if (maps_section_nr != removing_section_nr)
+			put_page_bootmem(page);
+	}
+}
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
 static void free_section_usemap(struct page *memmap, unsigned long *usemap)
 {
+	struct page *usemap_page;
+	unsigned long nr_pages;
+
 	if (!usemap)
 		return;
 
+	usemap_page = virt_to_page(usemap);
 	/*
 	 * Check to see if allocation came from hot-plug-add
 	 */
-	if (PageSlab(virt_to_page(usemap))) {
+	if (PageSlab(usemap_page)) {
 		kfree(usemap);
 		if (memmap)
 			__kfree_section_memmap(memmap, PAGES_PER_SECTION);
@@ -415,10 +449,19 @@
 	}
 
 	/*
-	 * TODO: Allocations came from bootmem - how do I free up ?
+	 * The usemap came from bootmem. This is packed with other usemaps
+	 * on the section which has pgdat at boot time. Just keep it as is now.
 	 */
-	printk(KERN_WARNING "Not freeing up allocations from bootmem "
-			"- leaking memory\n");
+
+	if (memmap) {
+		struct page *memmap_page;
+		memmap_page = virt_to_page(memmap);
+
+		nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
+			>> PAGE_SHIFT;
+
+		free_map_bootmem(memmap_page, nr_pages);
+	}
 }
 
 /*
Index: current/mm/page_alloc.c
===================================================================
--- current.orig/mm/page_alloc.c	2008-04-07 20:12:55.000000000 +0900
+++ current/mm/page_alloc.c	2008-04-07 20:13:29.000000000 +0900
@@ -568,7 +568,7 @@
 /*
  * permit the bootmem allocator to evade page validation on high-order frees
  */
-void __init __free_pages_bootmem(struct page *page, unsigned int order)
+void __free_pages_bootmem(struct page *page, unsigned int order)
 {
 	if (order == 0) {
 		__ClearPageReserved(page);
Index: current/mm/internal.h
===================================================================
--- current.orig/mm/internal.h	2008-04-07 20:12:55.000000000 +0900
+++ current/mm/internal.h	2008-04-07 20:13:29.000000000 +0900
@@ -34,8 +34,7 @@
 	atomic_dec(&page->_count);
 }
 
-extern void __init __free_pages_bootmem(struct page *page,
-						unsigned int order);
+extern void __free_pages_bootmem(struct page *page, unsigned int order);
 
 /*
  * function for dealing with page's order in buddy system.
Index: current/mm/memory_hotplug.c
===================================================================
--- current.orig/mm/memory_hotplug.c	2008-04-07 20:12:55.000000000 +0900
+++ current/mm/memory_hotplug.c	2008-04-07 20:13:29.000000000 +0900
@@ -199,6 +199,16 @@
 	return register_new_memory(__pfn_to_section(phys_start_pfn));
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+static int __remove_section(struct zone *zone, struct mem_section *ms)
+{
+	/*
+	 * XXX: Freeing memmap with vmemmap is not implement yet.
+	 *      This should be removed later.
+	 */
+	return -EBUSY;
+}
+#else
 static int __remove_section(struct zone *zone, struct mem_section *ms)
 {
 	unsigned long flags;
@@ -217,6 +227,7 @@
 	pgdat_resize_unlock(pgdat, &flags);
 	return 0;
 }
+#endif
 
 /*
  * Reasonably generic function for adding memory.  It is

-- 
Yasunori Goto