net/smc: use a workqueue to defer llc send

SMC handles deferred work in tasklets. As tasklets cannot sleep this
can result in rare EBUSY conditions, so defer this work in a work queue.
The high level api functions do not defer work because they can sleep
until the llc send is actually completed.

Signed-off-by: Karsten Graul <[e-mail]>
Signed-off-by: Ursula Braun <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/smc/smc_core.c

···
 		smc_ib_setup_per_ibdev(smcibdev);
 	get_random_bytes(rndvec, sizeof(rndvec));
 	lnk->psn_initial = rndvec[0] + (rndvec[1] << 8) + (rndvec[2] << 16);
-	smc_llc_link_init(lnk);
-	rc = smc_wr_alloc_link_mem(lnk);
+	rc = smc_llc_link_init(lnk);
 	if (rc)
 		goto free_lgr;
+	rc = smc_wr_alloc_link_mem(lnk);
+	if (rc)
+		goto clear_llc_lnk;
 	rc = smc_ib_create_protection_domain(lnk);
 	if (rc)
 		goto free_link_mem;
···
 	smc_ib_dealloc_protection_domain(lnk);
 free_link_mem:
 	smc_wr_free_link_mem(lnk);
+clear_llc_lnk:
+	smc_llc_link_clear(lnk);
 free_lgr:
 	kfree(lgr);
 out:
···
 static void smc_link_clear(struct smc_link *lnk)
 {
 	lnk->peer_qpn = 0;
+	smc_llc_link_clear(lnk);
 	smc_ib_modify_qp_reset(lnk);
 	smc_wr_free_link(lnk);
 	smc_ib_destroy_queue_pair(lnk);
···
 /* remove a link group */
 void smc_lgr_free(struct smc_link_group *lgr)
 {
-	smc_llc_link_flush(&lgr->lnk[SMC_SINGLE_LINK]);
 	smc_lgr_free_bufs(lgr);
 	smc_link_clear(&lgr->lnk[SMC_SINGLE_LINK]);
 	kfree(lgr);

net/smc/smc_core.h

···
 	u8			link_id;	/* unique # within link group */
 
 	enum smc_link_state	state;		/* state of link */
+	struct workqueue_struct *llc_wq;	/* single thread work queue */
 	struct completion	llc_confirm;	/* wait for rx of conf link */
 	struct completion	llc_confirm_resp; /* wait 4 rx of cnf lnk rsp */
 	int			llc_confirm_rc; /* rc from confirm link msg */

net/smc/smc_llc.c

···
 	return rc;
 }
 
+/* prepare an add link message */
+static void smc_llc_prep_add_link(struct smc_llc_msg_add_link *addllc,
+				  struct smc_link *link, u8 mac[],
+				  union ib_gid *gid,
+				  enum smc_llc_reqresp reqresp)
+{
+	memset(addllc, 0, sizeof(*addllc));
+	addllc->hd.common.type = SMC_LLC_ADD_LINK;
+	addllc->hd.length = sizeof(struct smc_llc_msg_add_link);
+	if (reqresp == SMC_LLC_RESP) {
+		addllc->hd.flags |= SMC_LLC_FLAG_RESP;
+		/* always reject more links for now */
+		addllc->hd.flags |= SMC_LLC_FLAG_ADD_LNK_REJ;
+		addllc->hd.add_link_rej_rsn = SMC_LLC_REJ_RSN_NO_ALT_PATH;
+	}
+	memcpy(addllc->sender_mac, mac, ETH_ALEN);
+	memcpy(addllc->sender_gid, gid, SMC_GID_SIZE);
+}
+
 /* send ADD LINK request or response */
 int smc_llc_send_add_link(struct smc_link *link, u8 mac[],
 			  union ib_gid *gid,
···
 	if (rc)
 		return rc;
 	addllc = (struct smc_llc_msg_add_link *)wr_buf;
-	memset(addllc, 0, sizeof(*addllc));
-	addllc->hd.common.type = SMC_LLC_ADD_LINK;
-	addllc->hd.length = sizeof(struct smc_llc_msg_add_link);
-	if (reqresp == SMC_LLC_RESP) {
-		addllc->hd.flags |= SMC_LLC_FLAG_RESP;
-		/* always reject more links for now */
-		addllc->hd.flags |= SMC_LLC_FLAG_ADD_LNK_REJ;
-		addllc->hd.add_link_rej_rsn = SMC_LLC_REJ_RSN_NO_ALT_PATH;
-	}
-	memcpy(addllc->sender_mac, mac, ETH_ALEN);
-	memcpy(addllc->sender_gid, gid, SMC_GID_SIZE);
+	smc_llc_prep_add_link(addllc, link, mac, gid, reqresp);
 	/* send llc message */
 	rc = smc_wr_tx_send(link, pend);
 	return rc;
+}
+
+/* prepare a delete link message */
+static void smc_llc_prep_delete_link(struct smc_llc_msg_del_link *delllc,
+				     struct smc_link *link,
+				     enum smc_llc_reqresp reqresp)
+{
+	memset(delllc, 0, sizeof(*delllc));
+	delllc->hd.common.type = SMC_LLC_DELETE_LINK;
+	delllc->hd.length = sizeof(struct smc_llc_msg_add_link);
+	if (reqresp == SMC_LLC_RESP)
+		delllc->hd.flags |= SMC_LLC_FLAG_RESP;
+	/* DEL_LINK_ALL because only 1 link supported */
+	delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ALL;
+	delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ORDERLY;
+	delllc->link_num = link->link_id;
 }
 
 /* send DELETE LINK request or response */
···
 	if (rc)
 		return rc;
 	delllc = (struct smc_llc_msg_del_link *)wr_buf;
-	memset(delllc, 0, sizeof(*delllc));
-	delllc->hd.common.type = SMC_LLC_DELETE_LINK;
-	delllc->hd.length = sizeof(struct smc_llc_msg_add_link);
-	if (reqresp == SMC_LLC_RESP)
-		delllc->hd.flags |= SMC_LLC_FLAG_RESP;
-	/* DEL_LINK_ALL because only 1 link supported */
-	delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ALL;
-	delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ORDERLY;
-	delllc->link_num = link->link_id;
+	smc_llc_prep_delete_link(delllc, link, reqresp);
 	/* send llc message */
 	rc = smc_wr_tx_send(link, pend);
 	return rc;
···
 	return rc;
 }
 
-/* send a prepared message */
-static int smc_llc_send_message(struct smc_link *link, void *llcbuf, int llclen)
+struct smc_llc_send_work {
+	struct work_struct work;
+	struct smc_link *link;
+	int llclen;
+	union smc_llc_msg llcbuf;
+};
+
+/* worker that sends a prepared message */
+static void smc_llc_send_message_work(struct work_struct *work)
 {
+	struct smc_llc_send_work *llcwrk = container_of(work,
+						struct smc_llc_send_work, work);
 	struct smc_wr_tx_pend_priv *pend;
 	struct smc_wr_buf *wr_buf;
 	int rc;
 
-	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
+	if (llcwrk->link->state == SMC_LNK_INACTIVE)
+		goto out;
+	rc = smc_llc_add_pending_send(llcwrk->link, &wr_buf, &pend);
 	if (rc)
-		return rc;
-	memcpy(wr_buf, llcbuf, llclen);
-	/* send llc message */
-	rc = smc_wr_tx_send(link, pend);
-	return rc;
+		goto out;
+	memcpy(wr_buf, &llcwrk->llcbuf, llcwrk->llclen);
+	smc_wr_tx_send(llcwrk->link, pend);
+out:
+	kfree(llcwrk);
+}
+
+/* copy llcbuf and schedule an llc send on link */
+static int smc_llc_send_message(struct smc_link *link, void *llcbuf, int llclen)
+{
+	struct smc_llc_send_work *wrk = kmalloc(sizeof(*wrk), GFP_ATOMIC);
+
+	if (!wrk)
+		return -ENOMEM;
+	INIT_WORK(&wrk->work, smc_llc_send_message_work);
+	wrk->link = link;
+	wrk->llclen = llclen;
+	memcpy(&wrk->llcbuf, llcbuf, llclen);
+	queue_work(link->llc_wq, &wrk->work);
+	return 0;
 }
 
 /********************************* receive ***********************************/
···
 		}
 
 		if (lgr->role == SMC_SERV) {
-			smc_llc_send_add_link(link,
+			smc_llc_prep_add_link(llc, link,
 					link->smcibdev->mac[link->ibport - 1],
 					&link->smcibdev->gid[link->ibport - 1],
 					SMC_LLC_REQ);
 
 		} else {
-			smc_llc_send_add_link(link,
+			smc_llc_prep_add_link(llc, link,
 					link->smcibdev->mac[link->ibport - 1],
 					&link->smcibdev->gid[link->ibport - 1],
 					SMC_LLC_RESP);
 		}
+		smc_llc_send_message(link, llc, sizeof(*llc));
 	}
 }
 
···
 	} else {
 		if (lgr->role == SMC_SERV) {
 			smc_lgr_forget(lgr);
-			smc_llc_send_delete_link(link, SMC_LLC_REQ);
+			smc_llc_prep_delete_link(llc, link, SMC_LLC_REQ);
+			smc_llc_send_message(link, llc, sizeof(*llc));
 		} else {
-			smc_llc_send_delete_link(link, SMC_LLC_RESP);
+			smc_llc_prep_delete_link(llc, link, SMC_LLC_RESP);
+			smc_llc_send_message(link, llc, sizeof(*llc));
 			smc_lgr_terminate(lgr);
 		}
 	}
···
 	}
 	next_interval = link->llc_testlink_time;
 out:
-	schedule_delayed_work(&link->llc_testlink_wrk, next_interval);
+	queue_delayed_work(link->llc_wq, &link->llc_testlink_wrk,
+			   next_interval);
 }
 
-void smc_llc_link_init(struct smc_link *link)
+int smc_llc_link_init(struct smc_link *link)
 {
+	struct smc_link_group *lgr = container_of(link, struct smc_link_group,
+						  lnk[SMC_SINGLE_LINK]);
+	link->llc_wq = alloc_ordered_workqueue("llc_wq-%x:%x)", WQ_MEM_RECLAIM,
+					       *((u32 *)lgr->id),
+					       link->link_id);
+	if (!link->llc_wq)
+		return -ENOMEM;
 	init_completion(&link->llc_confirm);
 	init_completion(&link->llc_confirm_resp);
 	init_completion(&link->llc_add);
···
 	init_completion(&link->llc_confirm_rkey);
 	init_completion(&link->llc_testlink_resp);
 	INIT_DELAYED_WORK(&link->llc_testlink_wrk, smc_llc_testlink_work);
+	return 0;
 }
 
 void smc_llc_link_active(struct smc_link *link, int testlink_time)
···
 	link->state = SMC_LNK_ACTIVE;
 	if (testlink_time) {
 		link->llc_testlink_time = testlink_time * HZ;
-		schedule_delayed_work(&link->llc_testlink_wrk,
-				      link->llc_testlink_time);
+		queue_delayed_work(link->llc_wq, &link->llc_testlink_wrk,
+				   link->llc_testlink_time);
 	}
 }
 
···
 }
 
 /* called in worker context */
-void smc_llc_link_flush(struct smc_link *link)
+void smc_llc_link_clear(struct smc_link *link)
 {
-	cancel_delayed_work_sync(&link->llc_testlink_wrk);
+	flush_workqueue(link->llc_wq);
+	destroy_workqueue(link->llc_wq);
 }
 
 /* register a new rtoken at the remote peer */

net/smc/smc_llc.h

···
 			  enum smc_llc_reqresp reqresp);
 int smc_llc_send_delete_link(struct smc_link *link,
 			     enum smc_llc_reqresp reqresp);
-void smc_llc_link_init(struct smc_link *link);
+int smc_llc_link_init(struct smc_link *link);
 void smc_llc_link_active(struct smc_link *link, int testlink_time);
 void smc_llc_link_inactive(struct smc_link *link);
-void smc_llc_link_flush(struct smc_link *link);
+void smc_llc_link_clear(struct smc_link *link);
 int smc_llc_do_confirm_rkey(struct smc_link *link,
 			    struct smc_buf_desc *rmb_desc);
 int smc_llc_init(void) __init;