netdev - [PATCH v2 2/2] mm/page_alloc: use a single function to free page

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Date:   Tue, 6 Nov 2018 13:30:37 +0800
From:   Aaron Lu <aaron.lu@...el.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Paweł Staszewski <pstaszewski@...are.pl>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Yoel Caspersen <yoel@...knet.dk>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>
Subject: [PATCH v2 2/2] mm/page_alloc: use a single function to free page

We have multiple places of freeing a page, most of them doing similar
things and a common function can be used to reduce code duplicate.

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

Signed-off-by: Aaron Lu <aaron.lu@...el.com>
---
v2: move comments close to code as suggested by Dave.

 mm/page_alloc.c | 36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 91a9a6af41a2..4faf6b7bf225 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4425,9 +4425,17 @@ 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, int nr)
 {
-	if (put_page_testzero(page)) {
+	VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
+
+	/*
+	 * Free a page by reducing its ref count by @nr.
+	 * If its refcount reaches 0, then according to its order:
+	 * order0: send to PCP;
+	 * high order: directly send to Buddy.
+	 */
+	if (page_ref_sub_and_test(page, nr)) {
 		if (order == 0)
 			free_unref_page(page);
 		else
@@ -4435,6 +4443,10 @@ void __free_pages(struct page *page, unsigned int order)
 	}
 }
 
+void __free_pages(struct page *page, unsigned int order)
+{
+	free_the_page(page, order, 1);
+}
 EXPORT_SYMBOL(__free_pages);
 
 void free_pages(unsigned long addr, unsigned int order)
@@ -4481,16 +4493,7 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 
 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);
-	}
+	free_the_page(page, compound_order(page), count);
 }
 EXPORT_SYMBOL(__page_frag_cache_drain);
 
@@ -4555,14 +4558,7 @@ 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)
-			free_unref_page(page);
-		else
-			__free_pages_ok(page, order);
-	}
+	free_the_page(page, compound_order(page), 1);
 }
 EXPORT_SYMBOL(page_frag_free);
 
-- 
2.17.2