[PATCH v2 net-next 1/2] net: prepare (struct ubuf_info)->refcnt conversion

[Eric Dumazet]

In order to convert this atomic_t refcnt to refcount_t,
we need to init the refcount to one to not trigger
a 0 -> 1 transition.

This also removes one atomic operation in fast path.

v2: removed dead code in sock_zerocopy_put_abort()
as suggested by Willem.

Signed-off-by: Eric Dumazet <eduma...@google.com>
---
 net/core/skbuff.c | 10 ++--------
 net/ipv4/tcp.c    |  2 --
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 
917da73d3ab3b82163cf0a9ee944da09cb5a391f..1a754d7896ceac1eb85e3b13c1422b4d6a88fedf
 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -963,7 +963,7 @@ struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, 
size_t size)
        uarg->len = 1;
        uarg->bytelen = size;
        uarg->zerocopy = 1;
-       atomic_set(&uarg->refcnt, 0);
+       atomic_set(&uarg->refcnt, 1);
        sock_hold(sk);
 
        return uarg;
@@ -1005,6 +1005,7 @@ struct ubuf_info *sock_zerocopy_realloc(struct sock *sk, 
size_t size,
                        uarg->len++;
                        uarg->bytelen = bytelen;
                        atomic_set(&sk->sk_zckey, ++next);
+                       sock_zerocopy_get(uarg);
                        return uarg;
                }
        }
@@ -1102,13 +1103,6 @@ void sock_zerocopy_put_abort(struct ubuf_info *uarg)
                atomic_dec(&sk->sk_zckey);
                uarg->len--;
 
-               /* sock_zerocopy_put expects a ref. Most sockets take one per
-                * skb, which is zero on abort. tcp_sendmsg holds one extra, to
-                * avoid an skb send inside the main loop triggering uarg free.
-                */
-               if (sk->sk_type != SOCK_STREAM)
-                       atomic_inc(&uarg->refcnt);
-
                sock_zerocopy_put(uarg);
        }
 }
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 
21ca2df274c5130a13d31a391a1408d779af34af..fff4d7bc3b8b46174e7bd0a04d7c212307e55cb5
 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1190,8 +1190,6 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr 
*msg, size_t size)
                        goto out_err;
                }
 
-               /* skb may be freed in main loop, keep extra ref on uarg */
-               sock_zerocopy_get(uarg);
                if (!(sk_check_csum_caps(sk) && sk->sk_route_caps & NETIF_F_SG))
                        uarg->zerocopy = 0;
        }
-- 
2.14.1.581.gf28d330327-goog