[RFC PATCH 09/26] mm: page_alloc: move expand() above compaction_capture()

[Johannes Weiner <hannes@cmpxchg.org>]

The next patch will allow compaction to capture from
larger-than-requested page blocks and free the remainder.

Rearrange the code in advance to make the diff more readable. No
functional change.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/page_alloc.c | 186 ++++++++++++++++++++++++------------------------
 1 file changed, 93 insertions(+), 93 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8e5996f8b4b4..cd86f80d7bbe 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -950,61 +950,6 @@ static inline void set_buddy_order(struct page *page, unsigned int order)
 	__SetPageBuddy(page);
 }
 
-#ifdef CONFIG_COMPACTION
-static inline struct capture_control *task_capc(struct zone *zone)
-{
-	struct capture_control *capc = current->capture_control;
-
-	return unlikely(capc && capc->cc) &&
-		!(current->flags & PF_KTHREAD) &&
-		!capc->page &&
-		capc->cc->zone == zone ? capc : NULL;
-}
-
-static inline bool
-compaction_capture(struct capture_control *capc, struct page *page,
-		   int order, int migratetype)
-{
-	if (!capc || order != capc->cc->order)
-		return false;
-
-	/* Do not accidentally pollute CMA or isolated regions*/
-	if (is_migrate_cma(migratetype) ||
-	    is_migrate_isolate(migratetype))
-		return false;
-
-	if (order >= pageblock_order) {
-		migratetype = capc->migratetype;
-		change_pageblock_range(page, order, migratetype);
-	} else if (migratetype == MIGRATE_MOVABLE) {
-		/*
-		 * Do not let lower order allocations pollute a
-		 * movable pageblock.  This might let an unmovable
-		 * request use a reclaimable pageblock and vice-versa
-		 * but no more than normal fallback logic which can
-		 * have trouble finding a high-order free page.
-		 */
-		return false;
-	}
-
-	capc->page = page;
-	return true;
-}
-
-#else
-static inline struct capture_control *task_capc(struct zone *zone)
-{
-	return NULL;
-}
-
-static inline bool
-compaction_capture(struct capture_control *capc, struct page *page,
-		   int order, int migratetype)
-{
-	return false;
-}
-#endif /* CONFIG_COMPACTION */
-
 static inline void account_freepages(struct page *page, struct zone *zone,
 				     int nr_pages, int migratetype)
 {
@@ -1072,6 +1017,99 @@ static inline void del_page_from_free_list(struct page *page, struct zone *zone,
 	account_freepages(page, zone, -(1 << order), migratetype);
 }
 
+/*
+ * The order of subdivision here is critical for the IO subsystem.
+ * Please do not alter this order without good reasons and regression
+ * testing. Specifically, as large blocks of memory are subdivided,
+ * the order in which smaller blocks are delivered depends on the order
+ * they're subdivided in this function. This is the primary factor
+ * influencing the order in which pages are delivered to the IO
+ * subsystem according to empirical testing, and this is also justified
+ * by considering the behavior of a buddy system containing a single
+ * large block of memory acted on by a series of small allocations.
+ * This behavior is a critical factor in sglist merging's success.
+ *
+ * -- nyc
+ */
+static inline void expand(struct zone *zone, struct page *page,
+	int low, int high, int migratetype)
+{
+	unsigned long size = 1 << high;
+
+	while (high > low) {
+		high--;
+		size >>= 1;
+		VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
+
+		/*
+		 * Mark as guard pages (or page), that will allow to
+		 * merge back to allocator when buddy will be freed.
+		 * Corresponding page table entries will not be touched,
+		 * pages will stay not present in virtual address space
+		 */
+		if (set_page_guard(zone, &page[size], high))
+			continue;
+
+		add_to_free_list(&page[size], zone, high, migratetype, false);
+		set_buddy_order(&page[size], high);
+	}
+}
+
+#ifdef CONFIG_COMPACTION
+static inline struct capture_control *task_capc(struct zone *zone)
+{
+	struct capture_control *capc = current->capture_control;
+
+	return unlikely(capc && capc->cc) &&
+		!(current->flags & PF_KTHREAD) &&
+		!capc->page &&
+		capc->cc->zone == zone ? capc : NULL;
+}
+
+static inline bool
+compaction_capture(struct capture_control *capc, struct page *page,
+		   int order, int migratetype)
+{
+	if (!capc || order != capc->cc->order)
+		return false;
+
+	/* Do not accidentally pollute CMA or isolated regions*/
+	if (is_migrate_cma(migratetype) ||
+	    is_migrate_isolate(migratetype))
+		return false;
+
+	if (order >= pageblock_order) {
+		migratetype = capc->migratetype;
+		change_pageblock_range(page, order, migratetype);
+	} else if (migratetype == MIGRATE_MOVABLE) {
+		/*
+		 * Do not let lower order allocations pollute a
+		 * movable pageblock.  This might let an unmovable
+		 * request use a reclaimable pageblock and vice-versa
+		 * but no more than normal fallback logic which can
+		 * have trouble finding a high-order free page.
+		 */
+		return false;
+	}
+
+	capc->page = page;
+	return true;
+}
+
+#else
+static inline struct capture_control *task_capc(struct zone *zone)
+{
+	return NULL;
+}
+
+static inline bool
+compaction_capture(struct capture_control *capc, struct page *page,
+		   int order, int migratetype)
+{
+	return false;
+}
+#endif /* CONFIG_COMPACTION */
+
 /*
  * If this is not the largest possible page, check if the buddy
  * of the next-highest order is free. If it is, it's possible
@@ -2345,44 +2383,6 @@ void __init init_cma_reserved_pageblock(struct page *page)
 }
 #endif
 
-/*
- * The order of subdivision here is critical for the IO subsystem.
- * Please do not alter this order without good reasons and regression
- * testing. Specifically, as large blocks of memory are subdivided,
- * the order in which smaller blocks are delivered depends on the order
- * they're subdivided in this function. This is the primary factor
- * influencing the order in which pages are delivered to the IO
- * subsystem according to empirical testing, and this is also justified
- * by considering the behavior of a buddy system containing a single
- * large block of memory acted on by a series of small allocations.
- * This behavior is a critical factor in sglist merging's success.
- *
- * -- nyc
- */
-static inline void expand(struct zone *zone, struct page *page,
-	int low, int high, int migratetype)
-{
-	unsigned long size = 1 << high;
-
-	while (high > low) {
-		high--;
-		size >>= 1;
-		VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
-
-		/*
-		 * Mark as guard pages (or page), that will allow to
-		 * merge back to allocator when buddy will be freed.
-		 * Corresponding page table entries will not be touched,
-		 * pages will stay not present in virtual address space
-		 */
-		if (set_page_guard(zone, &page[size], high))
-			continue;
-
-		add_to_free_list(&page[size], zone, high, migratetype, false);
-		set_buddy_order(&page[size], high);
-	}
-}
-
 static void check_new_page_bad(struct page *page)
 {
 	if (unlikely(page->flags & __PG_HWPOISON)) {
-- 
2.39.2