net/packet: constify packet_lookup_frame() and __tpacket_has_room()

Goal is to be able to use __tpacket_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 66fcfd5b51f82a861795e002e91d3cbc69ab545a..273bffd2130d36cceb9947540a8511a51895874a 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -460,10 +460,10 @@ static __u32 __packet_set_timestamp(struct packet_sock *po, void *frame,
        return ts_status;
 }
 
-static void *packet_lookup_frame(struct packet_sock *po,
-               struct packet_ring_buffer *rb,
-               unsigned int position,
-               int status)
+static void *packet_lookup_frame(const struct packet_sock *po,
+                                const struct packet_ring_buffer *rb,
+                                unsigned int position,
+                                int status)
 {
        unsigned int pg_vec_pos, frame_offset;
        union tpacket_uhdr h;
@@ -1198,12 +1198,12 @@ static void packet_free_pending(struct packet_sock *po)
 #define ROOM_LOW       0x1
 #define ROOM_NORMAL    0x2
 
-static bool __tpacket_has_room(struct packet_sock *po, int pow_off)
+static bool __tpacket_has_room(const struct packet_sock *po, int pow_off)
 {
        int idx, len;
 
-       len = po->rx_ring.frame_max + 1;
-       idx = po->rx_ring.head;
+       len = READ_ONCE(po->rx_ring.frame_max) + 1;
+       idx = READ_ONCE(po->rx_ring.head);
        if (pow_off)
                idx += len >> pow_off;
        if (idx >= len)