net/smc: mutex to protect the lgr against parallel reconfigurations

Introduce llc_conf_mutex in the link group which is used to protect the
buffers and lgr states against parallel link reconfiguration.
This ensures that new connections do not start to register buffers with
the links of a link group when link creation or termination is running.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 4 deletions

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index c905675017c7..4c3af05d76a5 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -448,11 +448,21 @@ out:
 static void smcr_buf_unuse(struct smc_buf_desc *rmb_desc,
 			   struct smc_link_group *lgr)
 {
+	int rc;
+
 	if (rmb_desc->is_conf_rkey && !list_empty(&lgr->list)) {
 		/* unregister rmb with peer */
-		smc_llc_do_delete_rkey(lgr, rmb_desc);
-		rmb_desc->is_conf_rkey = false;
+		rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY);
+		if (!rc) {
+			/* protect against smc_llc_cli_rkey_exchange() */
+			mutex_lock(&lgr->llc_conf_mutex);
+			smc_llc_do_delete_rkey(lgr, rmb_desc);
+			rmb_desc->is_conf_rkey = false;
+			mutex_unlock(&lgr->llc_conf_mutex);
+			smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl);
+		}
 	}
+
 	if (rmb_desc->is_reg_err) {
 		/* buf registration failed, reuse not possible */
 		mutex_lock(&lgr->rmbs_lock);
@@ -552,6 +562,7 @@ static void smcr_rtoken_clear_link(struct smc_link *lnk)
 	}
 }
 
+/* must be called under lgr->llc_conf_mutex lock */
 void smcr_link_clear(struct smc_link *lnk)
 {
 	struct smc_ib_device *smcibdev;
@@ -1170,7 +1181,9 @@ free_table:
 	return rc;
 }
 
-/* register a new rmb on IB device */
+/* register a new rmb on IB device,
+ * must be called under lgr->llc_conf_mutex lock
+ */
 int smcr_link_reg_rmb(struct smc_link *link, struct smc_buf_desc *rmb_desc)
 {
 	if (list_empty(&link->lgr->list))
@@ -1224,7 +1237,9 @@ int smcr_buf_map_lgr(struct smc_link *lnk)
 	return 0;
 }
 
-/* register all used buffers of lgr for a new link */
+/* register all used buffers of lgr for a new link,
+ * must be called under lgr->llc_conf_mutex lock
+ */
 int smcr_buf_reg_lgr(struct smc_link *lnk)
 {
 	struct smc_link_group *lgr = lnk->lgr;
@@ -1278,6 +1293,8 @@ static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
 {
 	int i, rc = 0;
 
+	/* protect against parallel link reconfiguration */
+	mutex_lock(&lgr->llc_conf_mutex);
 	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
 		struct smc_link *lnk = &lgr->lnk[i];
 
@@ -1289,6 +1306,7 @@ static int smcr_buf_map_usable_links(struct smc_link_group *lgr,
 		}
 	}
 out:
+	mutex_unlock(&lgr->llc_conf_mutex);
 	return rc;
 }