> On Aug 14, 2017, at 3:16 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
>
> Instead add a mechanism to ensure that the request doesn't disappear
> from underneath us while copying from the socket. We do this by
> preventing xprt_release() from freeing the XDR buffers until the
> flag RPC_TASK_MSG_RECV has been cleared from the request.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> include/linux/sunrpc/sched.h | 2 ++
> include/linux/sunrpc/xprt.h | 2 ++
> net/sunrpc/xprt.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> net/sunrpc/xprtsock.c | 27 ++++++++++++++++++++++-----
> 4 files changed, 68 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
> index 15bc1cd6ee5c..e972d9e05426 100644
> --- a/include/linux/sunrpc/sched.h
> +++ b/include/linux/sunrpc/sched.h
> @@ -141,6 +141,8 @@ struct rpc_task_setup {
> #define RPC_TASK_ACTIVE 2
> #define RPC_TASK_MSG_XMIT 3
> #define RPC_TASK_MSG_XMIT_WAIT 4
> +#define RPC_TASK_MSG_RECV 5
> +#define RPC_TASK_MSG_RECV_WAIT 6
>
> #define RPC_IS_RUNNING(t) test_bit(RPC_TASK_RUNNING, &(t)->tk_runstate)
> #define rpc_set_running(t) set_bit(RPC_TASK_RUNNING, &(t)->tk_runstate)
> diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
> index eab1c749e192..65b9e0224753 100644
> --- a/include/linux/sunrpc/xprt.h
> +++ b/include/linux/sunrpc/xprt.h
> @@ -372,6 +372,8 @@ void xprt_write_space(struct rpc_xprt *xprt);
> void xprt_adjust_cwnd(struct rpc_xprt *xprt, struct rpc_task *task, int result);
> struct rpc_rqst * xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid);
> void xprt_complete_rqst(struct rpc_task *task, int copied);
> +void xprt_pin_rqst(struct rpc_rqst *req);
> +void xprt_unpin_rqst(struct rpc_rqst *req);
> void xprt_release_rqst_cong(struct rpc_task *task);
> void xprt_disconnect_done(struct rpc_xprt *xprt);
> void xprt_force_disconnect(struct rpc_xprt *xprt);
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index 788c1b6138c2..62c379865f7c 100644
> --- a/net/sunrpc/xprt.c
> +++ b/net/sunrpc/xprt.c
> @@ -844,6 +844,47 @@ struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)
> }
> EXPORT_SYMBOL_GPL(xprt_lookup_rqst);
>
> +/**
> + * xprt_pin_rqst - Pin a request on the transport receive list
> + * @req: Request to pin
> + *
> + * Caller must ensure this is atomic with the call to xprt_lookup_rqst()
> + * so should be holding the xprt transport lock.
> + */
> +void xprt_pin_rqst(struct rpc_rqst *req)
> +{
> + set_bit(RPC_TASK_MSG_RECV, &req->rq_task->tk_runstate);
> +}
> +
> +/**
> + * xprt_unpin_rqst - Unpin a request on the transport receive list
> + * @req: Request to pin
> + *
> + * Caller should be holding the xprt transport lock.
> + */
> +void xprt_unpin_rqst(struct rpc_rqst *req)
> +{
> + struct rpc_task *task = req->rq_task;
> +
> + clear_bit(RPC_TASK_MSG_RECV, &task->tk_runstate);
> + if (test_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate))
> + wake_up_bit(&task->tk_runstate, RPC_TASK_MSG_RECV);
> +}
> +
> +static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)
> +__must_hold(&req->rq_xprt->transport_lock)
> +{
> + struct rpc_task *task = req->rq_task;
> + if (test_bit(RPC_TASK_MSG_RECV, &task->tk_runstate)) {
> + spin_unlock_bh(&req->rq_xprt->transport_lock);
> + set_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
> + wait_on_bit(&task->tk_runstate, RPC_TASK_MSG_RECV,
> + TASK_UNINTERRUPTIBLE);
> + clear_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
> + spin_lock_bh(&req->rq_xprt->transport_lock);
> + }
> +}
> +
> static void xprt_update_rtt(struct rpc_task *task)
> {
> struct rpc_rqst *req = task->tk_rqstp;
> @@ -1301,6 +1342,7 @@ void xprt_release(struct rpc_task *task)
> list_del(&req->rq_list);
> xprt->last_used = jiffies;
> xprt_schedule_autodisconnect(xprt);
> + xprt_wait_on_pinned_rqst(req);
> spin_unlock_bh(&xprt->transport_lock);
Is it OK to call wait_on_bit(TASK_UNINTERRUPTIBLE) while holding
a BH spin lock? This could be prone to deadlock.
> if (req->rq_buffer)
> xprt->ops->buf_free(task);
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 4f154d388748..222993fbaf99 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -973,6 +973,8 @@ static void xs_local_data_read_skb(struct rpc_xprt *xprt,
> rovr = xprt_lookup_rqst(xprt, *xp);
> if (!rovr)
> goto out_unlock;
> + xprt_pin_rqst(rovr);
> + spin_unlock_bh(&xprt->transport_lock);
> task = rovr->rq_task;
>
> copied = rovr->rq_private_buf.buflen;
> @@ -981,11 +983,14 @@ static void xs_local_data_read_skb(struct rpc_xprt *xprt,
>
> if (xs_local_copy_to_xdr(&rovr->rq_private_buf, skb)) {
> dprintk("RPC: sk_buff copy failed\n");
> - goto out_unlock;
> + spin_lock_bh(&xprt->transport_lock);
> + goto out_unpin;
> }
>
> + spin_lock_bh(&xprt->transport_lock);
> xprt_complete_rqst(task, copied);
> -
> +out_unpin:
> + xprt_unpin_rqst(rovr);
> out_unlock:
> spin_unlock_bh(&xprt->transport_lock);
> }
> @@ -1054,6 +1059,8 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
> rovr = xprt_lookup_rqst(xprt, *xp);
> if (!rovr)
> goto out_unlock;
> + xprt_pin_rqst(rovr);
> + spin_unlock_bh(&xprt->transport_lock);
> task = rovr->rq_task;
>
> if ((copied = rovr->rq_private_buf.buflen) > repsize)
> @@ -1062,14 +1069,17 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
> /* Suck it into the iovec, verify checksum if not done by hw. */
> if (csum_partial_copy_to_xdr(&rovr->rq_private_buf, skb)) {
> __UDPX_INC_STATS(sk, UDP_MIB_INERRORS);
> - goto out_unlock;
> + spin_lock_bh(&xprt->transport_lock);
> + goto out_unpin;
> }
>
> __UDPX_INC_STATS(sk, UDP_MIB_INDATAGRAMS);
>
> + spin_lock_bh(&xprt->transport_lock);
> xprt_adjust_cwnd(xprt, task, copied);
> xprt_complete_rqst(task, copied);
> -
> +out_unpin:
> + xprt_unpin_rqst(rovr);
> out_unlock:
> spin_unlock_bh(&xprt->transport_lock);
> }
> @@ -1351,12 +1361,15 @@ static inline int xs_tcp_read_reply(struct rpc_xprt *xprt,
> spin_unlock_bh(&xprt->transport_lock);
> return -1;
> }
> + xprt_pin_rqst(req);
> + spin_unlock_bh(&xprt->transport_lock);
>
> xs_tcp_read_common(xprt, desc, req);
>
> + spin_lock_bh(&xprt->transport_lock);
> if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
> xprt_complete_rqst(req->rq_task, transport->tcp_copied);
> -
> + xprt_unpin_rqst(req);
> spin_unlock_bh(&xprt->transport_lock);
> return 0;
> }
> @@ -1385,12 +1398,16 @@ static int xs_tcp_read_callback(struct rpc_xprt *xprt,
> xprt_force_disconnect(xprt);
> return -1;
> }
> + xprt_pin_rqst(req);
> + spin_unlock_bh(&xprt->transport_lock);
>
> dprintk("RPC: read callback XID %08x\n", ntohl(req->rq_xid));
> xs_tcp_read_common(xprt, desc, req);
>
> + spin_lock_bh(&xprt->transport_lock);
> if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
> xprt_complete_bc_request(req, transport->tcp_copied);
> + xprt_unpin_rqst(req);
> spin_unlock_bh(&xprt->transport_lock);
>
> return 0;
> --
> 2.13.5
>
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--
Chuck Lever
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