mm: meminit: only set page reserved in the memblock region

Currently each page struct is set as reserved upon initialization.  This
patch leaves the reserved bit clear and only sets the reserved bit when it
is known the memory was allocated by the bootmem allocator.  This makes it
easier to distinguish between uninitialised struct pages and reserved
struct pages in later patches.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Nathan Zimmer <nzimmer@sgi.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Tested-by: Nate Zimmer <nzimmer@sgi.com>
Tested-by: Waiman Long <waiman.long@hp.com>
Tested-by: Daniel J Blueman <daniel@numascale.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Robin Holt <robinmholt@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Waiman Long <waiman.long@hp.com>
Cc: Scott Norton <scott.norton@hp.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -1635,6 +1635,8 @@ extern void free_highmem_page(struct page *page);
 extern void adjust_managed_page_count(struct page *page, long count);
 extern void mem_init_print_info(const char *str);
 
+extern void reserve_bootmem_region(unsigned long start, unsigned long end);
+
 /* Free the reserved page into the buddy system, so it gets managed. */
 static inline void __free_reserved_page(struct page *page)
 {

mm/nobootmem.c

@@ -130,6 +130,9 @@ static unsigned long __init free_low_memory_core_early(void)
 
 	memblock_clear_hotplug(0, -1);
 
+	for_each_reserved_mem_region(i, &start, &end)
+		reserve_bootmem_region(start, end);
+
 	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &start, &end,
 				NULL)
 		count += __free_memory_core(start, end);

mm/page_alloc.c

@@ -774,7 +774,6 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	init_page_count(page);
 	page_mapcount_reset(page);
 	page_cpupid_reset_last(page);
-	SetPageReserved(page);
 
 	/*
 	 * Mark the block movable so that blocks are reserved for
@@ -809,6 +808,22 @@ static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
 	return __init_single_page(pfn_to_page(pfn), pfn, zone, nid);
 }
 
+/*
+ * Initialised pages do not have PageReserved set. This function is
+ * called for each range allocated by the bootmem allocator and
+ * marks the pages PageReserved. The remaining valid pages are later
+ * sent to the buddy page allocator.
+ */
+void reserve_bootmem_region(unsigned long start, unsigned long end)
+{
+	unsigned long start_pfn = PFN_DOWN(start);
+	unsigned long end_pfn = PFN_UP(end);
+
+	for (; start_pfn < end_pfn; start_pfn++)
+		if (pfn_valid(start_pfn))
+			SetPageReserved(pfn_to_page(start_pfn));
+}
+
 static bool free_pages_prepare(struct page *page, unsigned int order)
 {
 	bool compound = PageCompound(page);