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xprtrdma: Prevent dereferencing r_xprt->rx_ep after it is freed
r_xprt->rx_ep is known to be good while the transport's send lock is held. Otherwise additional references on rx_ep must be held when it is used outside of that lock's critical sections. For now, bump the rx_ep reference count once whenever there is at least one outstanding Receive WR. This avoids the memory bandwidth overhead of taking and releasing the reference count for every ib_post_recv() and Receive completion. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
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48778464bb
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2acc5cae29
@ -84,7 +84,8 @@ static void rpcrdma_rep_destroy(struct rpcrdma_rep *rep);
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static void rpcrdma_reps_unmap(struct rpcrdma_xprt *r_xprt);
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static void rpcrdma_mrs_create(struct rpcrdma_xprt *r_xprt);
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static void rpcrdma_mrs_destroy(struct rpcrdma_xprt *r_xprt);
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static int rpcrdma_ep_destroy(struct rpcrdma_ep *ep);
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static void rpcrdma_ep_get(struct rpcrdma_ep *ep);
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static int rpcrdma_ep_put(struct rpcrdma_ep *ep);
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static struct rpcrdma_regbuf *
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rpcrdma_regbuf_alloc(size_t size, enum dma_data_direction direction,
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gfp_t flags);
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@ -97,7 +98,8 @@ static void rpcrdma_regbuf_free(struct rpcrdma_regbuf *rb);
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*/
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static void rpcrdma_xprt_drain(struct rpcrdma_xprt *r_xprt)
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{
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struct rdma_cm_id *id = r_xprt->rx_ep->re_id;
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struct rpcrdma_ep *ep = r_xprt->rx_ep;
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struct rdma_cm_id *id = ep->re_id;
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/* Flush Receives, then wait for deferred Reply work
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* to complete.
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@ -108,6 +110,8 @@ static void rpcrdma_xprt_drain(struct rpcrdma_xprt *r_xprt)
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* local invalidations.
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*/
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ib_drain_sq(id->qp);
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rpcrdma_ep_put(ep);
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}
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/**
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@ -266,7 +270,7 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
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xprt_force_disconnect(xprt);
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goto disconnected;
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case RDMA_CM_EVENT_ESTABLISHED:
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kref_get(&ep->re_kref);
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rpcrdma_ep_get(ep);
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ep->re_connect_status = 1;
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rpcrdma_update_cm_private(ep, &event->param.conn);
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trace_xprtrdma_inline_thresh(ep);
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@ -289,7 +293,7 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
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ep->re_connect_status = -ECONNABORTED;
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disconnected:
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xprt_force_disconnect(xprt);
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return rpcrdma_ep_destroy(ep);
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return rpcrdma_ep_put(ep);
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default:
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break;
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}
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@ -345,7 +349,7 @@ out:
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return ERR_PTR(rc);
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}
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static void rpcrdma_ep_put(struct kref *kref)
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static void rpcrdma_ep_destroy(struct kref *kref)
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{
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struct rpcrdma_ep *ep = container_of(kref, struct rpcrdma_ep, re_kref);
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@ -369,13 +373,18 @@ static void rpcrdma_ep_put(struct kref *kref)
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module_put(THIS_MODULE);
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}
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static noinline void rpcrdma_ep_get(struct rpcrdma_ep *ep)
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{
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kref_get(&ep->re_kref);
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}
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/* Returns:
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* %0 if @ep still has a positive kref count, or
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* %1 if @ep was destroyed successfully.
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*/
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static int rpcrdma_ep_destroy(struct rpcrdma_ep *ep)
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static noinline int rpcrdma_ep_put(struct rpcrdma_ep *ep)
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{
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return kref_put(&ep->re_kref, rpcrdma_ep_put);
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return kref_put(&ep->re_kref, rpcrdma_ep_destroy);
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}
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static int rpcrdma_ep_create(struct rpcrdma_xprt *r_xprt)
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@ -492,7 +501,7 @@ static int rpcrdma_ep_create(struct rpcrdma_xprt *r_xprt)
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return 0;
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out_destroy:
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rpcrdma_ep_destroy(ep);
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rpcrdma_ep_put(ep);
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rdma_destroy_id(id);
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out_free:
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kfree(ep);
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@ -521,8 +530,12 @@ retry:
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ep->re_connect_status = 0;
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xprt_clear_connected(xprt);
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rpcrdma_reset_cwnd(r_xprt);
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/* Bump the ep's reference count while there are
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* outstanding Receives.
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*/
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rpcrdma_ep_get(ep);
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rpcrdma_post_recvs(r_xprt, true);
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rc = rpcrdma_sendctxs_create(r_xprt);
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@ -587,7 +600,7 @@ void rpcrdma_xprt_disconnect(struct rpcrdma_xprt *r_xprt)
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rpcrdma_mrs_destroy(r_xprt);
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rpcrdma_sendctxs_destroy(r_xprt);
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if (rpcrdma_ep_destroy(ep))
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if (rpcrdma_ep_put(ep))
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rdma_destroy_id(id);
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r_xprt->rx_ep = NULL;
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