net/smc: allow fallback after clc timeouts

If connection initialization fails for the LLC CONFIRM LINK or the
LLC ADD LINK step, fallback to TCP should be enabled. Thus
the negative return code -EAGAIN should switch to a positive timeout
reason code in these cases, and the internal CLC socket should
not have a set sk_err.
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/af_smc.c

@@ -336,7 +336,7 @@ static int smc_clnt_conf_first_link(struct smc_sock *smc)
 
 		rc = smc_clc_wait_msg(smc, &dclc, sizeof(dclc),
 				      SMC_CLC_DECLINE);
-		return rc;
+		return rc == -EAGAIN ? SMC_CLC_DECL_TIMEOUT_CL : rc;
 	}
 
 	if (link->llc_confirm_rc)
@@ -364,7 +364,7 @@ static int smc_clnt_conf_first_link(struct smc_sock *smc)
 
 		rc = smc_clc_wait_msg(smc, &dclc, sizeof(dclc),
 				      SMC_CLC_DECLINE);
-		return rc;
+		return rc == -EAGAIN ? SMC_CLC_DECL_TIMEOUT_AL : rc;
 	}
 
 	/* send add link reject message, only one link supported for now */
@@ -966,7 +966,7 @@ static int smc_serv_conf_first_link(struct smc_sock *smc)
 
 		rc = smc_clc_wait_msg(smc, &dclc, sizeof(dclc),
 				      SMC_CLC_DECLINE);
-		return rc;
+		return rc == -EAGAIN ? SMC_CLC_DECL_TIMEOUT_CL : rc;
 	}
 
 	if (link->llc_confirm_resp_rc)
@@ -987,7 +987,7 @@ static int smc_serv_conf_first_link(struct smc_sock *smc)
 
 		rc = smc_clc_wait_msg(smc, &dclc, sizeof(dclc),
 				      SMC_CLC_DECLINE);
-		return rc;
+		return rc == -EAGAIN ? SMC_CLC_DECL_TIMEOUT_AL : rc;
 	}
 
 	smc_llc_link_active(link, net->ipv4.sysctl_tcp_keepalive_time);

net/smc/smc_clc.c

@@ -297,6 +297,10 @@ int smc_clc_wait_msg(struct smc_sock *smc, void *buf, int buflen,
 	}
 	if (clc_sk->sk_err) {
 		reason_code = -clc_sk->sk_err;
+		if (clc_sk->sk_err == EAGAIN &&
+		    expected_type == SMC_CLC_DECLINE)
+			clc_sk->sk_err = 0; /* reset for fallback usage */
+		else
 			smc->sk.sk_err = clc_sk->sk_err;
 		goto out;
 	}
@@ -306,6 +310,7 @@ int smc_clc_wait_msg(struct smc_sock *smc, void *buf, int buflen,
 		goto out;
 	}
 	if (len < 0) {
+		if (len != -EAGAIN || expected_type != SMC_CLC_DECLINE)
 			smc->sk.sk_err = -len;
 		reason_code = len;
 		goto out;