memory hotplug: make alloc_bootmem_section()

alloc_bootmem_section() can allocate specified section's area.  This is used
for usemap to keep same section with pgdat by later patch.
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/bootmem.h

@@ -101,6 +101,8 @@ extern void reserve_bootmem_node(pg_data_t *pgdat,
 extern void free_bootmem_node(pg_data_t *pgdat,
 			      unsigned long addr,
 			      unsigned long size);
+extern void *alloc_bootmem_section(unsigned long size,
+				   unsigned long section_nr);
 
 #ifndef CONFIG_HAVE_ARCH_BOOTMEM_NODE
 #define alloc_bootmem_node(pgdat, x) \

mm/bootmem.c

@@ -545,6 +545,37 @@ void * __init __alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
 	return __alloc_bootmem(size, align, goal);
 }
 
+#ifdef CONFIG_SPARSEMEM
+void * __init alloc_bootmem_section(unsigned long size,
+				    unsigned long section_nr)
+{
+	void *ptr;
+	unsigned long limit, goal, start_nr, end_nr, pfn;
+	struct pglist_data *pgdat;
+
+	pfn = section_nr_to_pfn(section_nr);
+	goal = PFN_PHYS(pfn);
+	limit = PFN_PHYS(section_nr_to_pfn(section_nr + 1)) - 1;
+	pgdat = NODE_DATA(early_pfn_to_nid(pfn));
+	ptr = __alloc_bootmem_core(pgdat->bdata, size, SMP_CACHE_BYTES, goal,
+				   limit);
+
+	if (!ptr)
+		return NULL;
+
+	start_nr = pfn_to_section_nr(PFN_DOWN(__pa(ptr)));
+	end_nr = pfn_to_section_nr(PFN_DOWN(__pa(ptr) + size));
+	if (start_nr != section_nr || end_nr != section_nr) {
+		printk(KERN_WARNING "alloc_bootmem failed on section %ld.\n",
+		       section_nr);
+		free_bootmem_core(pgdat->bdata, __pa(ptr), size);
+		ptr = NULL;
+	}
+
+	return ptr;
+}
+#endif
+
 #ifndef ARCH_LOW_ADDRESS_LIMIT
 #define ARCH_LOW_ADDRESS_LIMIT	0xffffffffUL
 #endif