xprtrdma: Fix rpcrdma_reqs_reset()

Avoid FastReg operations getting MW_BIND_ERR after a reconnect.

rpcrdma_reqs_reset() is called on transport tear-down to get each
rpcrdma_req back into a clean state.

MRs on req->rl_registered are waiting for a FastReg, are already
registered, or are waiting for invalidation. If the transport is
being torn down when reqs_reset() is called, the matching LocalInv
might never be posted. That leaves these MR registered /and/ on
req->rl_free_mrs, where they can be re-used for the next
connection.

Since xprtrdma does not keep specific track of the MR state, it's
not possible to know what state these MRs are in, so the only safe
thing to do is release them immediately.

Fixes: 5de55ce9 ("xprtrdma: Release in-flight MRs on disconnect")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/frwr_ops.c

@@ -92,7 +92,8 @@ static void frwr_mr_put(struct rpcrdma_mr *mr)
 	rpcrdma_mr_push(mr, &mr->mr_req->rl_free_mrs);
 }
 
-/* frwr_reset - Place MRs back on the free list
+/**
+ * frwr_reset - Place MRs back on @req's free list
  * @req: request to reset
  *
  * Used after a failed marshal. For FRWR, this means the MRs

net/sunrpc/xprtrdma/verbs.c

@@ -897,6 +897,8 @@ static int rpcrdma_reqs_setup(struct rpcrdma_xprt *r_xprt)
 
 static void rpcrdma_req_reset(struct rpcrdma_req *req)
 {
+	struct rpcrdma_mr *mr;
+
 	/* Credits are valid for only one connection */
 	req->rl_slot.rq_cong = 0;
 
@@ -906,7 +908,19 @@ static void rpcrdma_req_reset(struct rpcrdma_req *req)
 	rpcrdma_regbuf_dma_unmap(req->rl_sendbuf);
 	rpcrdma_regbuf_dma_unmap(req->rl_recvbuf);
 
-	frwr_reset(req);
+	/* The verbs consumer can't know the state of an MR on the
+	 * req->rl_registered list unless a successful completion
+	 * has occurred, so they cannot be re-used.
+	 */
+	while ((mr = rpcrdma_mr_pop(&req->rl_registered))) {
+		struct rpcrdma_buffer *buf = &mr->mr_xprt->rx_buf;
+
+		spin_lock(&buf->rb_lock);
+		list_del(&mr->mr_all);
+		spin_unlock(&buf->rb_lock);
+
+		frwr_mr_release(mr);
+	}
 }
 
 /* ASSUMPTION: the rb_allreqs list is stable for the duration,