net/smc: fix work request handling

Wait for pending sends only when smc_switch_conns() found a link to move
the connections to. Do not wait during link freeing, this can lead to
permanent hang situations. And refuse to provide a new tx slot on an
unusable link.

Fixes: c6f02ebe ("net/smc: switch connections to alternate link")
Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_llc.c

@@ -1241,7 +1241,7 @@ static void smc_llc_process_cli_delete_link(struct smc_link_group *lgr)
 	smc_llc_send_message(lnk, &qentry->msg); /* response */
 
 	if (smc_link_downing(&lnk_del->state)) {
-		smc_switch_conns(lgr, lnk_del, false);
+		if (smc_switch_conns(lgr, lnk_del, false))
 			smc_wr_tx_wait_no_pending_sends(lnk_del);
 	}
 	smcr_link_clear(lnk_del, true);
@@ -1316,7 +1316,7 @@ static void smc_llc_process_srv_delete_link(struct smc_link_group *lgr)
 		goto out; /* asymmetric link already deleted */
 
 	if (smc_link_downing(&lnk_del->state)) {
-		smc_switch_conns(lgr, lnk_del, false);
+		if (smc_switch_conns(lgr, lnk_del, false))
 			smc_wr_tx_wait_no_pending_sends(lnk_del);
 	}
 	if (!list_empty(&lgr->list)) {

net/smc/smc_wr.c

@@ -169,6 +169,8 @@ void smc_wr_tx_cq_handler(struct ib_cq *ib_cq, void *cq_context)
 static inline int smc_wr_tx_get_free_slot_index(struct smc_link *link, u32 *idx)
 {
 	*idx = link->wr_tx_cnt;
+	if (!smc_link_usable(link))
+		return -ENOLINK;
 	for_each_clear_bit(*idx, link->wr_tx_mask, link->wr_tx_cnt) {
 		if (!test_and_set_bit(*idx, link->wr_tx_mask))
 			return 0;
@@ -560,15 +562,15 @@ void smc_wr_free_link(struct smc_link *lnk)
 {
 	struct ib_device *ibdev;
 
+	if (!lnk->smcibdev)
+		return;
+	ibdev = lnk->smcibdev->ibdev;
+
 	if (smc_wr_tx_wait_no_pending_sends(lnk))
 		memset(lnk->wr_tx_mask, 0,
 		       BITS_TO_LONGS(SMC_WR_BUF_CNT) *
 						sizeof(*lnk->wr_tx_mask));
 
-	if (!lnk->smcibdev)
-		return;
-	ibdev = lnk->smcibdev->ibdev;
-
 	if (lnk->wr_rx_dma_addr) {
 		ib_dma_unmap_single(ibdev, lnk->wr_rx_dma_addr,
 				    SMC_WR_BUF_SIZE * lnk->wr_rx_cnt,