[POWERPC] Fix handling of memreserve if the range lands in highmem

There were several issues if a memreserve range existed and happened
to be in highmem:

* The bootmem allocator is only aware of lowmem so calling
  reserve_bootmem with a highmem address would cause a BUG_ON
* All highmem pages were provided to the buddy allocator

Added a lmb_is_reserved() api that we now use to determine if a highem
page should continue to be PageReserved or provided to the buddy
allocator.

Also, we incorrectly reported the amount of pages reserved since all
highmem pages are initally marked reserved and we clear the
PageReserved flag as we "free" up the highmem pages.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/mm/lmb.c

@@ -342,3 +342,16 @@ void __init lmb_enforce_memory_limit(unsigned long memory_limit)
 		}
 	}
 }
+
+int __init lmb_is_reserved(unsigned long addr)
+{
+	int i;
+
+	for (i = 0; i < lmb.reserved.cnt; i++) {
+		unsigned long upper = lmb.reserved.region[i].base +
+				      lmb.reserved.region[i].size - 1;
+		if ((addr >= lmb.reserved.region[i].base) && (addr <= upper))
+			return 1;
+	}
+	return 0;
+}

arch/powerpc/mm/mem.c

@@ -213,15 +213,30 @@ void __init do_init_bootmem(void)
 	 */
 #ifdef CONFIG_HIGHMEM
 	free_bootmem_with_active_regions(0, total_lowmem >> PAGE_SHIFT);
+
+	/* reserve the sections we're already using */
+	for (i = 0; i < lmb.reserved.cnt; i++) {
+		unsigned long addr = lmb.reserved.region[i].base +
+				     lmb_size_bytes(&lmb.reserved, i) - 1;
+		if (addr < total_lowmem)
+			reserve_bootmem(lmb.reserved.region[i].base,
+					lmb_size_bytes(&lmb.reserved, i));
+		else if (lmb.reserved.region[i].base < total_lowmem) {
+			unsigned long adjusted_size = total_lowmem -
+				      lmb.reserved.region[i].base;
+			reserve_bootmem(lmb.reserved.region[i].base,
+					adjusted_size);
+		}
+	}
 #else
 	free_bootmem_with_active_regions(0, max_pfn);
-#endif
 
 	/* reserve the sections we're already using */
 	for (i = 0; i < lmb.reserved.cnt; i++)
 		reserve_bootmem(lmb.reserved.region[i].base,
 				lmb_size_bytes(&lmb.reserved, i));
 
+#endif
 	/* XXX need to clip this if using highmem? */
 	sparse_memory_present_with_active_regions(0);
 
@@ -334,11 +349,13 @@ void __init mem_init(void)
 		highmem_mapnr = total_lowmem >> PAGE_SHIFT;
 		for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
 			struct page *page = pfn_to_page(pfn);
-
+			if (lmb_is_reserved(pfn << PAGE_SHIFT))
+				continue;
 			ClearPageReserved(page);
 			init_page_count(page);
 			__free_page(page);
 			totalhigh_pages++;
+			reservedpages--;
 		}
 		totalram_pages += totalhigh_pages;
 		printk(KERN_DEBUG "High memory: %luk\n",