mm/page_ext: move functions around for minor cleanups to page_ext

1. move page_ext_get and page_ext_put down to remove forward
   declaration of lookup_page_ext.

2. move page_ext_init_flatmem_late down to existing non SPARS block to
   remove a new non SPARS block and to keep code for non SPARS tight.

Link: https://lkml.kernel.org/r/20230714114749.1743032-4-shikemeng@huaweicloud.comSigned-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_ext.c

@@ -90,7 +90,6 @@ static struct page_ext_operations *page_ext_ops[] __initdata = {
 unsigned long page_ext_size;
 
 static unsigned long total_usage;
-static struct page_ext *lookup_page_ext(const struct page *page);
 
 bool early_page_ext __meminitdata;
 static int __init setup_early_page_ext(char *str)
@@ -137,62 +136,16 @@ static void __init invoke_init_callbacks(void)
 	}
 }
 
-#ifndef CONFIG_SPARSEMEM
-void __init page_ext_init_flatmem_late(void)
-{
-	invoke_init_callbacks();
-}
-#endif
-
 static inline struct page_ext *get_entry(void *base, unsigned long index)
 {
 	return base + page_ext_size * index;
 }
 
-/**
- * page_ext_get() - Get the extended information for a page.
- * @page: The page we're interested in.
- *
- * Ensures that the page_ext will remain valid until page_ext_put()
- * is called.
- *
- * Return: NULL if no page_ext exists for this page.
- * Context: Any context.  Caller may not sleep until they have called
- * page_ext_put().
- */
-struct page_ext *page_ext_get(struct page *page)
-{
-	struct page_ext *page_ext;
-
-	rcu_read_lock();
-	page_ext = lookup_page_ext(page);
-	if (!page_ext) {
-		rcu_read_unlock();
-		return NULL;
-	}
-
-	return page_ext;
-}
-
-/**
- * page_ext_put() - Working with page extended information is done.
- * @page_ext: Page extended information received from page_ext_get().
- *
- * The page extended information of the page may not be valid after this
- * function is called.
- *
- * Return: None.
- * Context: Any context with corresponding page_ext_get() is called.
- */
-void page_ext_put(struct page_ext *page_ext)
+#ifndef CONFIG_SPARSEMEM
+void __init page_ext_init_flatmem_late(void)
 {
-	if (unlikely(!page_ext))
-		return;
-
-	rcu_read_unlock();
+	invoke_init_callbacks();
 }
-#ifndef CONFIG_SPARSEMEM
-
 
 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
 {
@@ -536,3 +489,46 @@ void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
 }
 
 #endif
+
+/**
+ * page_ext_get() - Get the extended information for a page.
+ * @page: The page we're interested in.
+ *
+ * Ensures that the page_ext will remain valid until page_ext_put()
+ * is called.
+ *
+ * Return: NULL if no page_ext exists for this page.
+ * Context: Any context.  Caller may not sleep until they have called
+ * page_ext_put().
+ */
+struct page_ext *page_ext_get(struct page *page)
+{
+	struct page_ext *page_ext;
+
+	rcu_read_lock();
+	page_ext = lookup_page_ext(page);
+	if (!page_ext) {
+		rcu_read_unlock();
+		return NULL;
+	}
+
+	return page_ext;
+}
+
+/**
+ * page_ext_put() - Working with page extended information is done.
+ * @page_ext: Page extended information received from page_ext_get().
+ *
+ * The page extended information of the page may not be valid after this
+ * function is called.
+ *
+ * Return: None.
+ * Context: Any context with corresponding page_ext_get() is called.
+ */
+void page_ext_put(struct page_ext *page_ext)
+{
+	if (unlikely(!page_ext))
+		return;
+
+	rcu_read_unlock();
+}