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    Subject[PATCH 5.4 419/475] SUNRPC: Fix socket waits for write buffer space
    Date
    From: Trond Myklebust <trond.myklebust@hammerspace.com>

    [ Upstream commit 7496b59f588dd52886fdbac7633608097543a0a5 ]

    The socket layer requires that we use the socket lock to protect changes
    to the sock->sk_write_pending field and others.

    Reported-by: Chuck Lever <chuck.lever@oracle.com>
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/sunrpc/xprtsock.c | 54 +++++++++++++++++++++++++++++++------------
    1 file changed, 39 insertions(+), 15 deletions(-)

    diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
    index 8ffc54b6661f..480e879e74ae 100644
    --- a/net/sunrpc/xprtsock.c
    +++ b/net/sunrpc/xprtsock.c
    @@ -872,12 +872,12 @@ static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen,
    /**
    * xs_nospace - handle transmit was incomplete
    * @req: pointer to RPC request
    + * @transport: pointer to struct sock_xprt
    *
    */
    -static int xs_nospace(struct rpc_rqst *req)
    +static int xs_nospace(struct rpc_rqst *req, struct sock_xprt *transport)
    {
    - struct rpc_xprt *xprt = req->rq_xprt;
    - struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
    + struct rpc_xprt *xprt = &transport->xprt;
    struct sock *sk = transport->inet;
    int ret = -EAGAIN;

    @@ -891,25 +891,49 @@ static int xs_nospace(struct rpc_rqst *req)

    /* Don't race with disconnect */
    if (xprt_connected(xprt)) {
    + struct socket_wq *wq;
    +
    + rcu_read_lock();
    + wq = rcu_dereference(sk->sk_wq);
    + set_bit(SOCKWQ_ASYNC_NOSPACE, &wq->flags);
    + rcu_read_unlock();
    +
    /* wait for more buffer space */
    + set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
    sk->sk_write_pending++;
    xprt_wait_for_buffer_space(xprt);
    } else
    ret = -ENOTCONN;

    spin_unlock(&xprt->transport_lock);
    + return ret;
    +}

    - /* Race breaker in case memory is freed before above code is called */
    - if (ret == -EAGAIN) {
    - struct socket_wq *wq;
    +static int xs_sock_nospace(struct rpc_rqst *req)
    +{
    + struct sock_xprt *transport =
    + container_of(req->rq_xprt, struct sock_xprt, xprt);
    + struct sock *sk = transport->inet;
    + int ret = -EAGAIN;

    - rcu_read_lock();
    - wq = rcu_dereference(sk->sk_wq);
    - set_bit(SOCKWQ_ASYNC_NOSPACE, &wq->flags);
    - rcu_read_unlock();
    + lock_sock(sk);
    + if (!sock_writeable(sk))
    + ret = xs_nospace(req, transport);
    + release_sock(sk);
    + return ret;
    +}

    - sk->sk_write_space(sk);
    - }
    +static int xs_stream_nospace(struct rpc_rqst *req)
    +{
    + struct sock_xprt *transport =
    + container_of(req->rq_xprt, struct sock_xprt, xprt);
    + struct sock *sk = transport->inet;
    + int ret = -EAGAIN;
    +
    + lock_sock(sk);
    + if (!sk_stream_memory_free(sk))
    + ret = xs_nospace(req, transport);
    + release_sock(sk);
    return ret;
    }

    @@ -996,7 +1020,7 @@ static int xs_local_send_request(struct rpc_rqst *req)
    case -ENOBUFS:
    break;
    case -EAGAIN:
    - status = xs_nospace(req);
    + status = xs_stream_nospace(req);
    break;
    default:
    dprintk("RPC: sendmsg returned unrecognized error %d\n",
    @@ -1068,7 +1092,7 @@ static int xs_udp_send_request(struct rpc_rqst *req)
    /* Should we call xs_close() here? */
    break;
    case -EAGAIN:
    - status = xs_nospace(req);
    + status = xs_sock_nospace(req);
    break;
    case -ENETUNREACH:
    case -ENOBUFS:
    @@ -1181,7 +1205,7 @@ static int xs_tcp_send_request(struct rpc_rqst *req)
    /* Should we call xs_close() here? */
    break;
    case -EAGAIN:
    - status = xs_nospace(req);
    + status = xs_stream_nospace(req);
    break;
    case -ECONNRESET:
    case -ECONNREFUSED:
    --
    2.35.1


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