netdev - [PATCH net-next v7 2/4] page_pool: halve BIAS_MAX for multiple user references of a fragment

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Date: Wed,  6 Dec 2023 18:54:17 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	hawk@...nel.org,
	ilias.apalodimas@...aro.org,
	linyunsheng@...wei.com
Cc: netdev@...r.kernel.org,
	linux-mm@...ck.org,
	jasowang@...hat.com,
	liangchen.linux@...il.com
Subject: [PATCH net-next v7 2/4] page_pool: halve BIAS_MAX for multiple user references of a fragment

Referring to patch [1], in order to support multiple users referencing the
same fragment and prevent overflow from pp_ref_count growing, the initial
value of pp_ref_count is halved, leaving room for pp_ref_count to increment
before the page is drained.

[1]
https://lore.kernel.org/all/20211009093724.10539-3-linyunsheng@huawei.com/

Signed-off-by: Liang Chen <liangchen.linux@...il.com>
Reviewed-by: Yunsheng Lin <linyunsheng@...wei.com>
---
 net/core/page_pool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 106220b1f89c..436f7ffea7b4 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -26,7 +26,7 @@
 #define DEFER_TIME (msecs_to_jiffies(1000))
 #define DEFER_WARN_INTERVAL (60 * HZ)
 
-#define BIAS_MAX	LONG_MAX
+#define BIAS_MAX	(LONG_MAX >> 1)
 
 #ifdef CONFIG_PAGE_POOL_STATS
 /* alloc_stat_inc is intended to be used in softirq context */
-- 
2.31.1