mm/page_alloc.c: use a single function to free page

There are multiple places of freeing a page, they all do the same things
so a common function can be used to reduce code duplicate.

It also avoids bug fixed in one function but left in another.

Link: http://lkml.kernel.org/r/20181119134834.17765-3-aaron.lu@intel.comSigned-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Pankaj gupta <pagupta@redhat.com>
Cc: Pawel Staszewski <pstaszewski@itcare.pl>
Cc: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -4427,16 +4427,19 @@ unsigned long get_zeroed_page(gfp_t gfp_mask)
 }
 EXPORT_SYMBOL(get_zeroed_page);
 
-void __free_pages(struct page *page, unsigned int order)
+static inline void free_the_page(struct page *page, unsigned int order)
 {
-	if (put_page_testzero(page)) {
-		if (order == 0)
+	if (order == 0)		/* Via pcp? */
 		free_unref_page(page);
 	else
 		__free_pages_ok(page, order);
-	}
 }
 
+void __free_pages(struct page *page, unsigned int order)
+{
+	if (put_page_testzero(page))
+		free_the_page(page, order);
+}
 EXPORT_SYMBOL(__free_pages);
 
 void free_pages(unsigned long addr, unsigned int order)
@@ -4485,14 +4488,8 @@ void __page_frag_cache_drain(struct page *page, unsigned int count)
 {
 	VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
 
-	if (page_ref_sub_and_test(page, count)) {
-		unsigned int order = compound_order(page);
-
-		if (order == 0)
-			free_unref_page(page);
-		else
-			__free_pages_ok(page, order);
-	}
+	if (page_ref_sub_and_test(page, count))
+		free_the_page(page, compound_order(page));
 }
 EXPORT_SYMBOL(__page_frag_cache_drain);
 
@@ -4557,14 +4554,8 @@ void page_frag_free(void *addr)
 {
 	struct page *page = virt_to_head_page(addr);
 
-	if (unlikely(put_page_testzero(page))) {
-		unsigned int order = compound_order(page);
-
-		if (order == 0)		/* Via pcp? */
-			free_unref_page(page);
-		else
-			__free_pages_ok(page, order);
-	}
+	if (unlikely(put_page_testzero(page)))
+		free_the_page(page, compound_order(page));
 }
 EXPORT_SYMBOL(page_frag_free);