netdev - [PATCH net-next 4/8] net/packet: constify __packet_rcv_has

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Message-Id: <20190612165233.109749-5-edumazet@google.com>
Date:   Wed, 12 Jun 2019 09:52:29 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Mahesh Bandewar <maheshb@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 4/8] net/packet: constify __packet_rcv_has_room()

Goal is use the helper without lock being held.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/packet/af_packet.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 5ef63d0c3ad0a184a03429fdd52cad26349647d1..a0564855ed9dca4be37f70ed81c6dee1b38aca39 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1224,15 +1224,18 @@ static bool __tpacket_v3_has_room(const struct packet_sock *po, int pow_off)
 	return prb_lookup_block(po, &po->rx_ring, idx, TP_STATUS_KERNEL);
 }
 
-static int __packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
+static int __packet_rcv_has_room(const struct packet_sock *po,
+				 const struct sk_buff *skb)
 {
-	struct sock *sk = &po->sk;
+	const struct sock *sk = &po->sk;
 	int ret = ROOM_NONE;
 
 	if (po->prot_hook.func != tpacket_rcv) {
-		int avail = sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)
-					  - (skb ? skb->truesize : 0);
-		if (avail > (sk->sk_rcvbuf >> ROOM_POW_OFF))
+		int rcvbuf = READ_ONCE(sk->sk_rcvbuf);
+		int avail = rcvbuf - atomic_read(&sk->sk_rmem_alloc)
+				   - (skb ? skb->truesize : 0);
+
+		if (avail > (rcvbuf >> ROOM_POW_OFF))
 			return ROOM_NORMAL;
 		else if (avail > 0)
 			return ROOM_LOW;
-- 
2.22.0.rc2.383.gf4fbbf30c2-goog