[PATCHv2] libfc: Update rport reference counting

[Hannes Reinecke <hare@suse.de>]

Originally libfc would just be initializing the refcount to '1',
and using the disc_mutex to synchronize if and when the final put
should be happening.
This has a race condition as the mutex might be delayed, causing
other threads to access an invalid structure.
This patch updates the rport reference counting to increase the
reference every time 'rport_lookup' is called, and decreases
the reference correspondingly.
This removes the need to hold 'disc_mutex' when removing the
structure, and avoids the above race condition.

Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/fcoe/fcoe_ctlr.c |  7 +------
 drivers/scsi/libfc/fc_lport.c | 19 ++++++++++-------
 drivers/scsi/libfc/fc_rport.c | 49 ++++++++++++++++++++++---------------------
 3 files changed, 38 insertions(+), 37 deletions(-)

diff --git a/drivers/scsi/fcoe/fcoe_ctlr.c b/drivers/scsi/fcoe/fcoe_ctlr.c
index 3e83d48..ada4bde 100644
--- a/drivers/scsi/fcoe/fcoe_ctlr.c
+++ b/drivers/scsi/fcoe/fcoe_ctlr.c
@@ -2496,14 +2496,13 @@ static int fcoe_ctlr_vn_lookup(struct fcoe_ctlr *fip, u32 port_id, u8 *mac)
 	struct fcoe_rport *frport;
 	int ret = -1;
 
-	rcu_read_lock();
 	rdata = lport->tt.rport_lookup(lport, port_id);
 	if (rdata) {
 		frport = fcoe_ctlr_rport(rdata);
 		memcpy(mac, frport->enode_mac, ETH_ALEN);
 		ret = 0;
+		kref_put(&rdata->kref, lport->tt.rport_destroy);
 	}
-	rcu_read_unlock();
 	return ret;
 }
 
@@ -2585,11 +2584,7 @@ static void fcoe_ctlr_vn_beacon(struct fcoe_ctlr *fip,
 		fcoe_ctlr_vn_send(fip, FIP_SC_VN_PROBE_REQ, fcoe_all_vn2vn, 0);
 		return;
 	}
-	mutex_lock(&lport->disc.disc_mutex);
 	rdata = lport->tt.rport_lookup(lport, new->ids.port_id);
-	if (rdata)
-		kref_get(&rdata->kref);
-	mutex_unlock(&lport->disc.disc_mutex);
 	if (rdata) {
 		if (rdata->ids.node_name == new->ids.node_name &&
 		    rdata->ids.port_name == new->ids.port_name) {
diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index e01a298..b9b44da 100644
--- a/drivers/scsi/libfc/fc_lport.c
+++ b/drivers/scsi/libfc/fc_lport.c
@@ -2090,7 +2090,7 @@ int fc_lport_bsg_request(struct fc_bsg_job *job)
 	struct fc_rport *rport;
 	struct fc_rport_priv *rdata;
 	int rc = -EINVAL;
-	u32 did;
+	u32 did, tov;
 
 	job->reply->reply_payload_rcv_len = 0;
 	if (rsp)
@@ -2121,15 +2121,20 @@ int fc_lport_bsg_request(struct fc_bsg_job *job)
 
 	case FC_BSG_HST_CT:
 		did = ntoh24(job->request->rqst_data.h_ct.port_id);
-		if (did == FC_FID_DIR_SERV)
+		if (did == FC_FID_DIR_SERV) {
 			rdata = lport->dns_rdata;
-		else
+			if (!rdata)
+				break;
+			tov = rdata->e_d_tov;
+		} else {
 			rdata = lport->tt.rport_lookup(lport, did);
+			if (!rdata)
+				break;
+			tov = rdata->e_d_tov;
+			kref_put(&rdata->kref, lport->tt.rport_destroy);
+		}
 
-		if (!rdata)
-			break;
-
-		rc = fc_lport_ct_request(job, lport, did, rdata->e_d_tov);
+		rc = fc_lport_ct_request(job, lport, did, tov);
 		break;
 
 	case FC_BSG_HST_ELS_NOLOGIN:
diff --git a/drivers/scsi/libfc/fc_rport.c b/drivers/scsi/libfc/fc_rport.c
index 589ff9a..93f5961 100644
--- a/drivers/scsi/libfc/fc_rport.c
+++ b/drivers/scsi/libfc/fc_rport.c
@@ -95,17 +95,23 @@ static const char *fc_rport_state_names[] = {
  * @lport:   The local port to lookup the remote port on
  * @port_id: The remote port ID to look up
  *
- * The caller must hold either disc_mutex or rcu_read_lock().
+ * The reference count of the fc_rport_priv structure is
+ * increased by one.
  */
 static struct fc_rport_priv *fc_rport_lookup(const struct fc_lport *lport,
 					     u32 port_id)
 {
-	struct fc_rport_priv *rdata;
+	struct fc_rport_priv *rdata = NULL, *tmp_rdata;
 
-	list_for_each_entry_rcu(rdata, &lport->disc.rports, peers)
-		if (rdata->ids.port_id == port_id)
-			return rdata;
-	return NULL;
+	rcu_read_lock();
+	list_for_each_entry_rcu(tmp_rdata, &lport->disc.rports, peers)
+		if (tmp_rdata->ids.port_id == port_id &&
+		    kref_get_unless_zero(&tmp_rdata->kref)) {
+			rdata = tmp_rdata;
+			break;
+		}
+	rcu_read_unlock();
+	return rdata;
 }
 
 /**
@@ -340,7 +346,6 @@ static void fc_rport_work(struct work_struct *work)
 			fc_remote_port_delete(rport);
 		}
 
-		mutex_lock(&lport->disc.disc_mutex);
 		mutex_lock(&rdata->rp_mutex);
 		if (rdata->rp_state == RPORT_ST_DELETE) {
 			if (port_id == FC_FID_DIR_SERV) {
@@ -370,7 +375,6 @@ static void fc_rport_work(struct work_struct *work)
 				fc_rport_enter_ready(rdata);
 			mutex_unlock(&rdata->rp_mutex);
 		}
-		mutex_unlock(&lport->disc.disc_mutex);
 		break;
 
 	default:
@@ -702,7 +706,7 @@ out:
 err:
 	mutex_unlock(&rdata->rp_mutex);
 put:
-	kref_put(&rdata->kref, rdata->local_port->tt.rport_destroy);
+	kref_put(&rdata->kref, lport->tt.rport_destroy);
 	return;
 bad:
 	FC_RPORT_DBG(rdata, "Bad FLOGI response\n");
@@ -762,8 +766,6 @@ static void fc_rport_recv_flogi_req(struct fc_lport *lport,
 	FC_RPORT_ID_DBG(lport, sid, "Received FLOGI request\n");
 
 	disc = &lport->disc;
-	mutex_lock(&disc->disc_mutex);
-
 	if (!lport->point_to_multipoint) {
 		rjt_data.reason = ELS_RJT_UNSUP;
 		rjt_data.explan = ELS_EXPL_NONE;
@@ -808,7 +810,7 @@ static void fc_rport_recv_flogi_req(struct fc_lport *lport,
 		mutex_unlock(&rdata->rp_mutex);
 		rjt_data.reason = ELS_RJT_FIP;
 		rjt_data.explan = ELS_EXPL_NOT_NEIGHBOR;
-		goto reject;
+		goto reject_put;
 	case RPORT_ST_FLOGI:
 	case RPORT_ST_PLOGI_WAIT:
 	case RPORT_ST_PLOGI:
@@ -825,13 +827,13 @@ static void fc_rport_recv_flogi_req(struct fc_lport *lport,
 		mutex_unlock(&rdata->rp_mutex);
 		rjt_data.reason = ELS_RJT_BUSY;
 		rjt_data.explan = ELS_EXPL_NONE;
-		goto reject;
+		goto reject_put;
 	}
 	if (fc_rport_login_complete(rdata, fp)) {
 		mutex_unlock(&rdata->rp_mutex);
 		rjt_data.reason = ELS_RJT_LOGIC;
 		rjt_data.explan = ELS_EXPL_NONE;
-		goto reject;
+		goto reject_put;
 	}
 
 	fp = fc_frame_alloc(lport, sizeof(*flp));
@@ -851,12 +853,13 @@ static void fc_rport_recv_flogi_req(struct fc_lport *lport,
 		fc_rport_state_enter(rdata, RPORT_ST_PLOGI_WAIT);
 out:
 	mutex_unlock(&rdata->rp_mutex);
-	mutex_unlock(&disc->disc_mutex);
+	kref_put(&rdata->kref, lport->tt.rport_destroy);
 	fc_frame_free(rx_fp);
 	return;
 
+reject_put:
+	kref_put(&rdata->kref, lport->tt.rport_destroy);
 reject:
-	mutex_unlock(&disc->disc_mutex);
 	lport->tt.seq_els_rsp_send(rx_fp, ELS_LS_RJT, &rjt_data);
 	fc_frame_free(rx_fp);
 }
@@ -923,7 +926,7 @@ out:
 	fc_frame_free(fp);
 err:
 	mutex_unlock(&rdata->rp_mutex);
-	kref_put(&rdata->kref, rdata->local_port->tt.rport_destroy);
+	kref_put(&rdata->kref, lport->tt.rport_destroy);
 }
 
 static bool
@@ -1477,14 +1480,11 @@ static void fc_rport_recv_els_req(struct fc_lport *lport, struct fc_frame *fp)
 	struct fc_rport_priv *rdata;
 	struct fc_seq_els_data els_data;
 
-	mutex_lock(&lport->disc.disc_mutex);
 	rdata = lport->tt.rport_lookup(lport, fc_frame_sid(fp));
-	if (!rdata) {
-		mutex_unlock(&lport->disc.disc_mutex);
+	if (!rdata)
 		goto reject;
-	}
+
 	mutex_lock(&rdata->rp_mutex);
-	mutex_unlock(&lport->disc.disc_mutex);
 
 	switch (rdata->rp_state) {
 	case RPORT_ST_PRLI:
@@ -1494,6 +1494,7 @@ static void fc_rport_recv_els_req(struct fc_lport *lport, struct fc_frame *fp)
 		break;
 	default:
 		mutex_unlock(&rdata->rp_mutex);
+		kref_put(&rdata->kref, lport->tt.rport_destroy);
 		goto reject;
 	}
 
@@ -1524,6 +1525,7 @@ static void fc_rport_recv_els_req(struct fc_lport *lport, struct fc_frame *fp)
 	}
 
 	mutex_unlock(&rdata->rp_mutex);
+	kref_put(&rdata->kref, rdata->local_port->tt.rport_destroy);
 	return;
 
 reject:
@@ -1907,7 +1909,6 @@ static void fc_rport_recv_logo_req(struct fc_lport *lport, struct fc_frame *fp)
 
 	sid = fc_frame_sid(fp);
 
-	mutex_lock(&lport->disc.disc_mutex);
 	rdata = lport->tt.rport_lookup(lport, sid);
 	if (rdata) {
 		mutex_lock(&rdata->rp_mutex);
@@ -1916,10 +1917,10 @@ static void fc_rport_recv_logo_req(struct fc_lport *lport, struct fc_frame *fp)
 
 		fc_rport_enter_delete(rdata, RPORT_EV_LOGO);
 		mutex_unlock(&rdata->rp_mutex);
+		kref_put(&rdata->kref, rdata->local_port->tt.rport_destroy);
 	} else
 		FC_RPORT_ID_DBG(lport, sid,
 				"Received LOGO from non-logged-in port\n");
-	mutex_unlock(&lport->disc.disc_mutex);
 	fc_frame_free(fp);
 }
 
-- 
1.8.5.6