net/packet: constify prb_lookup_block() and __tpacket_v3_has_room()

Goal is to be able to use __tpacket_v3_has_room() without holding
a lock.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 273bffd2130d36cceb9947540a8511a51895874a..5ef63d0c3ad0a184a03429fdd52cad26349647d1 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1082,10 +1082,10 @@ static void *packet_current_rx_frame(struct packet_sock *po,
        }
 }
 
-static void *prb_lookup_block(struct packet_sock *po,
-                                    struct packet_ring_buffer *rb,
-                                    unsigned int idx,
-                                    int status)
+static void *prb_lookup_block(const struct packet_sock *po,
+                             const struct packet_ring_buffer *rb,
+                             unsigned int idx,
+                             int status)
 {
        struct tpacket_kbdq_core *pkc  = GET_PBDQC_FROM_RB(rb);
        struct tpacket_block_desc *pbd = GET_PBLOCK_DESC(pkc, idx);
@@ -1211,12 +1211,12 @@ static bool __tpacket_has_room(const struct packet_sock *po, int pow_off)
        return packet_lookup_frame(po, &po->rx_ring, idx, TP_STATUS_KERNEL);
 }
 
-static bool __tpacket_v3_has_room(struct packet_sock *po, int pow_off)
+static bool __tpacket_v3_has_room(const struct packet_sock *po, int pow_off)
 {
        int idx, len;
 
-       len = po->rx_ring.prb_bdqc.knum_blocks;
-       idx = po->rx_ring.prb_bdqc.kactive_blk_num;
+       len = READ_ONCE(po->rx_ring.prb_bdqc.knum_blocks);
+       idx = READ_ONCE(po->rx_ring.prb_bdqc.kactive_blk_num);
        if (pow_off)
                idx += len >> pow_off;
        if (idx >= len)