linux-kernel - [RFC PATCH v1 05/50] net/rds/bind.c: Use prandom_u32

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Message-Id: <202003281643.02SGh78v026162@sdf.org>
Date:   Fri, 29 Nov 2019 17:42:15 -0500
From:   George Spelvin <lkml@....org>
To:     linux-kernel@...r.kernel.org, lkml@....org
Cc:     Ka-Cheong Poon <ka-cheong.poon@...cle.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        linux-rdma@...r.kernel.org, rds-devel@....oracle.com
Subject: [RFC PATCH v1 05/50] net/rds/bind.c: Use prandom_u32_max()

max_t(u16, prandom_u32(), 2) generates 2 three times as often as
any other value.  Operating modulo 65534 improves uniformity.

Signed-off-by: George Spelvin <lkml@....org>
Cc: Ka-Cheong Poon <ka-cheong.poon@...cle.com>
Cc: Santosh Shilimkar <santosh.shilimkar@...cle.com>
Cc: linux-rdma@...r.kernel.org
Cc: rds-devel@....oracle.com
---
 net/rds/bind.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/bind.c b/net/rds/bind.c
index 5b5fb4ca8d3e5..8293044767b83 100644
--- a/net/rds/bind.c
+++ b/net/rds/bind.c
@@ -104,7 +104,7 @@ static int rds_add_bound(struct rds_sock *rs, const struct in6_addr *addr,
 			return -EINVAL;
 		last = rover;
 	} else {
-		rover = max_t(u16, prandom_u32(), 2);
+		rover = 2 + prandom_u32_max(65534);
 		last = rover - 1;
 	}
 
-- 
2.26.0