mm, page_alloc: don't duplicate code in free_pcp_prepare

The new free_pcp_prepare() function shares a lot of code with
free_pages_prepare(), which makes this a maintenance risk when some
future patch modifies only one of them.  We should be able to achieve
the same effect (skipping free_pages_check() from !DEBUG_VM configs) by
adding a parameter to free_pages_prepare() and making it inline, so the
checks (and the order != 0 parts) are eliminated from the call from
free_pcp_prepare().

!DEBUG_VM: bloat-o-meter reports no difference, as my gcc was already
inlining free_pages_prepare() and the elimination seems to work as
expected

DEBUG_VM bloat-o-meter:

  add/remove: 0/1 grow/shrink: 2/0 up/down: 1035/-778 (257)
  function                                     old     new   delta
  __free_pages_ok                              297    1060    +763
  free_hot_cold_page                           480     752    +272
  free_pages_prepare                           778       -    -778

Here inlining didn't occur before, and added some code, but it's ok for
a debug option.

[akpm@linux-foundation.org: fix build]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -991,47 +991,77 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
 	return ret;
 }
 
-static bool free_pages_prepare(struct page *page, unsigned int order);
-
-#ifdef CONFIG_DEBUG_VM
-static inline bool free_pcp_prepare(struct page *page)
+static __always_inline bool free_pages_prepare(struct page *page,
+					unsigned int order, bool check_free)
 {
-	return free_pages_prepare(page, 0);
-}
+	int bad = 0;
 
-static inline bool bulkfree_pcp_prepare(struct page *page)
-{
-	return false;
-}
-#else
-static bool free_pcp_prepare(struct page *page)
-{
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
-	trace_mm_page_free(page, 0);
-	kmemcheck_free_shadow(page, 0);
-	kasan_free_pages(page, 0);
+	trace_mm_page_free(page, order);
+	kmemcheck_free_shadow(page, order);
+	kasan_free_pages(page, order);
+
+	/*
+	 * Check tail pages before head page information is cleared to
+	 * avoid checking PageCompound for order-0 pages.
+	 */
+	if (unlikely(order)) {
+		bool compound = PageCompound(page);
+		int i;
+
+		VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
 
+		for (i = 1; i < (1 << order); i++) {
+			if (compound)
+				bad += free_tail_pages_check(page, page + i);
+			if (unlikely(free_pages_check(page + i))) {
+				bad++;
+				continue;
+			}
+			(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+		}
+	}
 	if (PageAnonHead(page))
 		page->mapping = NULL;
+	if (check_free)
+		bad += free_pages_check(page);
+	if (bad)
+		return false;
 
-	reset_page_owner(page, 0);
+	page_cpupid_reset_last(page);
+	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+	reset_page_owner(page, order);
 
 	if (!PageHighMem(page)) {
 		debug_check_no_locks_freed(page_address(page),
-					   PAGE_SIZE);
+					   PAGE_SIZE << order);
 		debug_check_no_obj_freed(page_address(page),
-					   PAGE_SIZE);
+					   PAGE_SIZE << order);
 	}
-	arch_free_page(page, 0);
-	kernel_poison_pages(page, 0, 0);
-	kernel_map_pages(page, 0, 0);
+	arch_free_page(page, order);
+	kernel_poison_pages(page, 1 << order, 0);
+	kernel_map_pages(page, 1 << order, 0);
 
-	page_cpupid_reset_last(page);
-	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
 	return true;
 }
 
+#ifdef CONFIG_DEBUG_VM
+static inline bool free_pcp_prepare(struct page *page)
+{
+	return free_pages_prepare(page, 0, true);
+}
+
+static inline bool bulkfree_pcp_prepare(struct page *page)
+{
+	return false;
+}
+#else
+static bool free_pcp_prepare(struct page *page)
+{
+	return free_pages_prepare(page, 0, false);
+}
+
 static bool bulkfree_pcp_prepare(struct page *page)
 {
 	return free_pages_check(page);
@@ -1201,66 +1231,13 @@ void __meminit reserve_bootmem_region(unsigned long start, unsigned long end)
 	}
 }
 
-static bool free_pages_prepare(struct page *page, unsigned int order)
-{
-	int bad = 0;
-
-	VM_BUG_ON_PAGE(PageTail(page), page);
-
-	trace_mm_page_free(page, order);
-	kmemcheck_free_shadow(page, order);
-	kasan_free_pages(page, order);
-
-	/*
-	 * Check tail pages before head page information is cleared to
-	 * avoid checking PageCompound for order-0 pages.
-	 */
-	if (unlikely(order)) {
-		bool compound = PageCompound(page);
-		int i;
-
-		VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
-
-		for (i = 1; i < (1 << order); i++) {
-			if (compound)
-				bad += free_tail_pages_check(page, page + i);
-			if (unlikely(free_pages_check(page + i))) {
-				bad++;
-				continue;
-			}
-			(page + i)->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
-		}
-	}
-	if (PageAnonHead(page))
-		page->mapping = NULL;
-	bad += free_pages_check(page);
-	if (bad)
-		return false;
-
-	page_cpupid_reset_last(page);
-	page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
-	reset_page_owner(page, order);
-
-	if (!PageHighMem(page)) {
-		debug_check_no_locks_freed(page_address(page),
-					   PAGE_SIZE << order);
-		debug_check_no_obj_freed(page_address(page),
-					   PAGE_SIZE << order);
-	}
-	arch_free_page(page, order);
-	kernel_poison_pages(page, 1 << order, 0);
-	kernel_map_pages(page, 1 << order, 0);
-
-	return true;
-}
-
 static void __free_pages_ok(struct page *page, unsigned int order)
 {
 	unsigned long flags;
 	int migratetype;
 	unsigned long pfn = page_to_pfn(page);
 
-	if (!free_pages_prepare(page, order))
+	if (!free_pages_prepare(page, order, true))
 		return;
 
 	migratetype = get_pfnblock_migratetype(page, pfn);