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From: Chuck Lever <chuck.lever@oracle.com>
To: trondmy@hammerspace.com
Cc: linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org
Subject: [PATCH v3 10/26] xprtrdma: Fix cwnd update ordering
Date: Mon, 19 Apr 2021 14:02:41 -0400	[thread overview]
Message-ID: <161885536143.38598.9604745938847259595.stgit@manet.1015granger.net> (raw)
In-Reply-To: <161885481568.38598.16682844600209775665.stgit@manet.1015granger.net>

After a reconnect, the reply handler is opening the cwnd (and thus
enabling more RPC Calls to be sent) /before/ rpcrdma_post_recvs()
can post enough Receive WRs to receive their replies. This causes an
RNR and the new connection is lost immediately.

The race is most clearly exposed when KASAN and disconnect injection
are enabled. This slows down rpcrdma_rep_create() enough to allow
the send side to post a bunch of RPC Calls before the Receive
completion handler can invoke ib_post_recv().

Fixes: 2ae50ad68cd7 ("xprtrdma: Close window between waking RPC senders and posting Receives")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/rpc_rdma.c  |    3 ++-
 net/sunrpc/xprtrdma/verbs.c     |   10 +++++-----
 net/sunrpc/xprtrdma/xprt_rdma.h |    2 +-
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 292f066d006e..21ddd78a8c35 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -1430,9 +1430,10 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *rep)
 		credits = 1;	/* don't deadlock */
 	else if (credits > r_xprt->rx_ep->re_max_requests)
 		credits = r_xprt->rx_ep->re_max_requests;
+	rpcrdma_post_recvs(r_xprt, credits + (buf->rb_bc_srv_max_requests << 1),
+			   false);
 	if (buf->rb_credits != credits)
 		rpcrdma_update_cwnd(r_xprt, credits);
-	rpcrdma_post_recvs(r_xprt, false);
 
 	req = rpcr_to_rdmar(rqst);
 	if (unlikely(req->rl_reply))
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 0ade69501061..5a2871c4561f 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -544,7 +544,7 @@ int rpcrdma_xprt_connect(struct rpcrdma_xprt *r_xprt)
 	 * outstanding Receives.
 	 */
 	rpcrdma_ep_get(ep);
-	rpcrdma_post_recvs(r_xprt, true);
+	rpcrdma_post_recvs(r_xprt, 1, true);
 
 	rc = rdma_connect(ep->re_id, &ep->re_remote_cma);
 	if (rc)
@@ -1395,21 +1395,21 @@ int rpcrdma_post_sends(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 /**
  * rpcrdma_post_recvs - Refill the Receive Queue
  * @r_xprt: controlling transport instance
- * @temp: mark Receive buffers to be deleted after use
+ * @needed: current credit grant
+ * @temp: mark Receive buffers to be deleted after one use
  *
  */
-void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp)
+void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, int needed, bool temp)
 {
 	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
 	struct rpcrdma_ep *ep = r_xprt->rx_ep;
 	struct ib_recv_wr *wr, *bad_wr;
 	struct rpcrdma_rep *rep;
-	int needed, count, rc;
+	int count, rc;
 
 	rc = 0;
 	count = 0;
 
-	needed = buf->rb_credits + (buf->rb_bc_srv_max_requests << 1);
 	if (likely(ep->re_receive_count > needed))
 		goto out;
 	needed -= ep->re_receive_count;
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 31404326f29f..2504f67af63e 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -462,7 +462,7 @@ int rpcrdma_xprt_connect(struct rpcrdma_xprt *r_xprt);
 void rpcrdma_xprt_disconnect(struct rpcrdma_xprt *r_xprt);
 
 int rpcrdma_post_sends(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req);
-void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, bool temp);
+void rpcrdma_post_recvs(struct rpcrdma_xprt *r_xprt, int needed, bool temp);
 
 /*
  * Buffer calls - xprtrdma/verbs.c



  parent reply	other threads:[~2021-04-19 18:02 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-19 18:01 [PATCH v3 00/26] NFS/RDMA client patches for next Chuck Lever
2021-04-19 18:01 ` [PATCH v3 01/26] SUNRPC: Move fault injection call sites Chuck Lever
2021-04-19 18:05   ` Chuck Lever III
2021-04-19 18:01 ` [PATCH v3 02/26] SUNRPC: Remove trace_xprt_transmit_queued Chuck Lever
2021-04-19 18:01 ` [PATCH v3 03/26] SUNRPC: Add tracepoint that fires when an RPC is retransmitted Chuck Lever
2021-04-19 18:02 ` [PATCH v3 04/26] xprtrdma: Avoid Receive Queue wrapping Chuck Lever
2021-04-19 18:02 ` [PATCH v3 05/26] xprtrdma: Do not refresh Receive Queue while it is draining Chuck Lever
2021-04-19 18:02 ` [PATCH v3 06/26] xprtrdma: Put flushed Receives on free list instead of destroying them Chuck Lever
2021-04-19 18:02 ` [PATCH v3 07/26] xprtrdma: Improve locking around rpcrdma_rep destruction Chuck Lever
2021-04-23 21:06   ` Trond Myklebust
2021-04-24 17:39     ` Chuck Lever III
2021-04-24 17:59       ` Trond Myklebust
2021-04-19 18:02 ` [PATCH v3 08/26] xprtrdma: Improve commentary around rpcrdma_reps_unmap() Chuck Lever
2021-04-19 18:02 ` [PATCH v3 09/26] xprtrdma: Improve locking around rpcrdma_rep creation Chuck Lever
2021-04-19 18:02 ` Chuck Lever [this message]
2021-04-19 18:02 ` [PATCH v3 11/26] xprtrdma: Delete rpcrdma_recv_buffer_put() Chuck Lever
2021-04-19 18:02 ` [PATCH v3 12/26] xprtrdma: rpcrdma_mr_pop() already does list_del_init() Chuck Lever
2021-04-19 18:03 ` [PATCH v3 13/26] xprtrdma: Rename frwr_release_mr() Chuck Lever
2021-04-19 18:03 ` [PATCH v3 14/26] xprtrdma: Clarify use of barrier in frwr_wc_localinv_done() Chuck Lever
2021-04-19 18:03 ` [PATCH v3 15/26] xprtrdma: Do not recycle MR after FastReg/LocalInv flushes Chuck Lever
2021-04-25 14:19   ` Dan Aloni
2021-04-25 16:21     ` Chuck Lever III
2021-04-25 17:00       ` Dan Aloni
2021-04-19 18:03 ` [PATCH v3 16/26] xprtrdma: Do not wake RPC consumer on a failed LocalInv Chuck Lever
2021-04-19 18:03 ` [PATCH v3 17/26] xprtrdma: Avoid Send Queue wrapping Chuck Lever
2021-04-19 18:03 ` [PATCH v3 18/26] xprtrdma: Add tracepoints showing FastReg WRs and remote invalidation Chuck Lever
2021-04-19 18:03 ` [PATCH v3 19/26] xprtrdma: Add an rpcrdma_mr_completion_class Chuck Lever
2021-04-19 18:03 ` [PATCH v3 20/26] xprtrdma: Don't display r_xprt memory addresses in tracepoints Chuck Lever
2021-04-19 18:03 ` [PATCH v3 21/26] xprtrdma: Remove the RPC/RDMA QP event handler Chuck Lever
2021-04-19 18:03 ` [PATCH v3 22/26] xprtrdma: Move fr_cid to struct rpcrdma_mr Chuck Lever
2021-04-19 18:04 ` [PATCH v3 23/26] xprtrdma: Move cqe " Chuck Lever
2021-04-19 18:04 ` [PATCH v3 24/26] xprtrdma: Move fr_linv_done field " Chuck Lever
2021-04-19 18:04 ` [PATCH v3 25/26] xprtrdma: Move the Work Request union " Chuck Lever
2021-04-19 18:04 ` [PATCH v3 26/26] xprtrdma: Move fr_mr field " Chuck Lever

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