From 2acc5cae292355f5f18ad377a2a966e7f03c8fec Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Mon, 15 Jun 2020 09:20:52 -0400 Subject: [PATCH] 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 Signed-off-by: Anna Schumaker --- net/sunrpc/xprtrdma/verbs.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c index 2ae348377806ab..b021baa4b28df0 100644 --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -84,7 +84,8 @@ static void rpcrdma_rep_destroy(struct rpcrdma_rep *rep); static void rpcrdma_reps_unmap(struct rpcrdma_xprt *r_xprt); static void rpcrdma_mrs_create(struct rpcrdma_xprt *r_xprt); static void rpcrdma_mrs_destroy(struct rpcrdma_xprt *r_xprt); -static int rpcrdma_ep_destroy(struct rpcrdma_ep *ep); +static void rpcrdma_ep_get(struct rpcrdma_ep *ep); +static int rpcrdma_ep_put(struct rpcrdma_ep *ep); static struct rpcrdma_regbuf * rpcrdma_regbuf_alloc(size_t size, enum dma_data_direction direction, gfp_t flags); @@ -97,7 +98,8 @@ static void rpcrdma_regbuf_free(struct rpcrdma_regbuf *rb); */ static void rpcrdma_xprt_drain(struct rpcrdma_xprt *r_xprt) { - struct rdma_cm_id *id = r_xprt->rx_ep->re_id; + struct rpcrdma_ep *ep = r_xprt->rx_ep; + struct rdma_cm_id *id = ep->re_id; /* Flush Receives, then wait for deferred Reply work * to complete. @@ -108,6 +110,8 @@ static void rpcrdma_xprt_drain(struct rpcrdma_xprt *r_xprt) * local invalidations. */ ib_drain_sq(id->qp); + + rpcrdma_ep_put(ep); } /** @@ -266,7 +270,7 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event) xprt_force_disconnect(xprt); goto disconnected; case RDMA_CM_EVENT_ESTABLISHED: - kref_get(&ep->re_kref); + rpcrdma_ep_get(ep); ep->re_connect_status = 1; rpcrdma_update_cm_private(ep, &event->param.conn); trace_xprtrdma_inline_thresh(ep); @@ -289,7 +293,7 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event) ep->re_connect_status = -ECONNABORTED; disconnected: xprt_force_disconnect(xprt); - return rpcrdma_ep_destroy(ep); + return rpcrdma_ep_put(ep); default: break; } @@ -345,7 +349,7 @@ static struct rdma_cm_id *rpcrdma_create_id(struct rpcrdma_xprt *r_xprt, return ERR_PTR(rc); } -static void rpcrdma_ep_put(struct kref *kref) +static void rpcrdma_ep_destroy(struct kref *kref) { struct rpcrdma_ep *ep = container_of(kref, struct rpcrdma_ep, re_kref); @@ -369,13 +373,18 @@ static void rpcrdma_ep_put(struct kref *kref) module_put(THIS_MODULE); } +static noinline void rpcrdma_ep_get(struct rpcrdma_ep *ep) +{ + kref_get(&ep->re_kref); +} + /* Returns: * %0 if @ep still has a positive kref count, or * %1 if @ep was destroyed successfully. */ -static int rpcrdma_ep_destroy(struct rpcrdma_ep *ep) +static noinline int rpcrdma_ep_put(struct rpcrdma_ep *ep) { - return kref_put(&ep->re_kref, rpcrdma_ep_put); + return kref_put(&ep->re_kref, rpcrdma_ep_destroy); } static int rpcrdma_ep_create(struct rpcrdma_xprt *r_xprt) @@ -492,7 +501,7 @@ static int rpcrdma_ep_create(struct rpcrdma_xprt *r_xprt) return 0; out_destroy: - rpcrdma_ep_destroy(ep); + rpcrdma_ep_put(ep); rdma_destroy_id(id); out_free: kfree(ep); @@ -521,8 +530,12 @@ int rpcrdma_xprt_connect(struct rpcrdma_xprt *r_xprt) ep->re_connect_status = 0; xprt_clear_connected(xprt); - rpcrdma_reset_cwnd(r_xprt); + + /* Bump the ep's reference count while there are + * outstanding Receives. + */ + rpcrdma_ep_get(ep); rpcrdma_post_recvs(r_xprt, true); rc = rpcrdma_sendctxs_create(r_xprt); @@ -587,7 +600,7 @@ void rpcrdma_xprt_disconnect(struct rpcrdma_xprt *r_xprt) rpcrdma_mrs_destroy(r_xprt); rpcrdma_sendctxs_destroy(r_xprt); - if (rpcrdma_ep_destroy(ep)) + if (rpcrdma_ep_put(ep)) rdma_destroy_id(id); r_xprt->rx_ep = NULL;