[SCSI] libfc: convert rport lookup to be RCU safe

To allow LLD to do lookups on rports without grabbing a mutex,
make them RCU-safe.  The caller of lport->tt.rport_lookup will
have the choice of holding disc_mutex or the rcu_read_lock().

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

2 files changed, 21 insertions, 7 deletions

diff --git a/drivers/scsi/libfc/fc_disc.c b/drivers/scsi/libfc/fc_disc.c
index c7985da88099..d0fa9a0ddc8d 100644
--- a/drivers/scsi/libfc/fc_disc.c
+++ b/drivers/scsi/libfc/fc_disc.c
@@ -63,12 +63,12 @@ static void fc_disc_restart(struct fc_disc *);
 void fc_disc_stop_rports(struct fc_disc *disc)
 {
         struct fc_lport *lport;
-        struct fc_rport_priv *rdata, *next;
+        struct fc_rport_priv *rdata;
 
         lport = disc->lport;
 
         mutex_lock(&disc->disc_mutex);
-        list_for_each_entry_safe(rdata, next, &disc->rports, peers)
+        list_for_each_entry_rcu(rdata, &disc->rports, peers)
                 lport->tt.rport_logoff(rdata);
         mutex_unlock(&disc->disc_mutex);
 }
@@ -292,7 +292,7 @@ static void fc_disc_done(struct fc_disc *disc, enum fc_disc_event event)
          * Skip ports which were never discovered.  These are the dNS port
          * and ports which were created by PLOGI.
          */
-        list_for_each_entry(rdata, &disc->rports, peers) {
+        list_for_each_entry_rcu(rdata, &disc->rports, peers) {
                 if (!rdata->disc_id)
                         continue;
                 if (rdata->disc_id == disc->disc_id)
diff --git a/drivers/scsi/libfc/fc_rport.c b/drivers/scsi/libfc/fc_rport.c
index 363cde30c940..6b569732f892 100644
--- a/drivers/scsi/libfc/fc_rport.c
+++ b/drivers/scsi/libfc/fc_rport.c
@@ -95,13 +95,15 @@ static const char *fc_rport_state_names[] = {
  * fc_rport_lookup() - Lookup a remote port by port_id
  * @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().
  */
 static struct fc_rport_priv *fc_rport_lookup(const struct fc_lport *lport,
                                              u32 port_id)
 {
         struct fc_rport_priv *rdata;
 
-        list_for_each_entry(rdata, &lport->disc.rports, peers)
+        list_for_each_entry_rcu(rdata, &lport->disc.rports, peers)
                 if (rdata->ids.port_id == port_id)
                         return rdata;
         return NULL;
@@ -146,11 +148,23 @@ static struct fc_rport_priv *fc_rport_create(struct fc_lport *lport,
         INIT_DELAYED_WORK(&rdata->retry_work, fc_rport_timeout);
         INIT_WORK(&rdata->event_work, fc_rport_work);
         if (port_id != FC_FID_DIR_SERV)
-                list_add(&rdata->peers, &lport->disc.rports);
+                list_add_rcu(&rdata->peers, &lport->disc.rports);
         return rdata;
 }
 
 /**
+ * fc_rport_free_rcu() - Free a remote port
+ * @rcu: The rcu_head structure inside the remote port
+ */
+static void fc_rport_free_rcu(struct rcu_head *rcu)
+{
+        struct fc_rport_priv *rdata;
+
+        rdata = container_of(rcu, struct fc_rport_priv, rcu);
+        kfree(rdata);
+}
+
+/**
  * fc_rport_destroy() - Free a remote port after last reference is released
  * @kref: The remote port's kref
  */
@@ -159,7 +173,7 @@ static void fc_rport_destroy(struct kref *kref)
         struct fc_rport_priv *rdata;
 
         rdata = container_of(kref, struct fc_rport_priv, kref);
-        kfree(rdata);
+        call_rcu(&rdata->rcu, fc_rport_free_rcu);
 }
 
 /**
@@ -334,7 +348,7 @@ static void fc_rport_work(struct work_struct *work)
                                 mutex_unlock(&rdata->rp_mutex);
                         } else {
                                 FC_RPORT_DBG(rdata, "work delete\n");
-                                list_del(&rdata->peers);
+                                list_del_rcu(&rdata->peers);
                                 mutex_unlock(&rdata->rp_mutex);
                                 kref_put(&rdata->kref, lport->tt.rport_destroy);
                         }