[PATCH 1/3] svcrdma: Grant credits from the clamped sc_max_requests

[Chuck Lever <cel@kernel.org>]

svc_rdma_accept() computes sc_fc_credits from sc_max_requests before
the Receive Queue depth is checked against the device's max_qp_wr.
When that check lowers sc_max_requests, the credit grant keeps the
original value, so the server advertises more credits than it has
Receives posted. A client that uses the full grant overruns the
Receive Queue, and the connection is lost with an RNR error.

Set sc_fc_credits after the clamp so the grant matches the number
of Receives the server posts.

Fixes: fc2e69db82c1 ("svcrdma: Clean up comment in svc_rdma_accept()")
Signed-off-by: Chuck Lever <cel@kernel.org>
---
 net/sunrpc/xprtrdma/svc_rdma_transport.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 927269598ac2..f949601b2144 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -471,7 +471,6 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
 	newxprt->sc_max_requests = svcrdma_max_requests;
 	newxprt->sc_max_bc_requests = svcrdma_max_bc_requests;
 	newxprt->sc_recv_batch = RPCRDMA_MAX_RECV_BATCH;
-	newxprt->sc_fc_credits = cpu_to_be32(newxprt->sc_max_requests);
 
 	/* Qualify the transport's resource defaults with the
 	 * capabilities of this particular device.
@@ -492,6 +491,8 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
 		newxprt->sc_max_bc_requests = 2;
 	}
 
+	newxprt->sc_fc_credits = cpu_to_be32(newxprt->sc_max_requests);
+
 	/* Estimate the needed number of rdma_rw contexts. The maximum
 	 * Read and Write chunks have one segment each. Each request
 	 * can involve one Read chunk and either a Write chunk or Reply
-- 
2.54.0