[SCSI] libfc: add hook for FC-4 provider registration

Allow FC-4 provider modules to hook into libfc, mostly for targets.
This should allow any FC-4 module to handle PRLI requests and maintain
process-association states.

Each provider registers its ops with libfc and then will be called for
any incoming PRLI for that FC-4 type on any instance.   The provider
can decide whether to handle that particular instance using any method
it likes, such as ACLs or other configuration information.

A count is kept of the number of successful PRLIs from the remote port.
Providers are called back with an implicit PRLO when the remote port
is about to be deleted or has been reset.

fc_lport_recv_req() now sends incoming FC-4 requests to FC-4 providers,
and there is a built-in provider always registered for handling
incoming ELS requests.

The call to provider recv() routines uses rcu_read_lock()
so that providers aren't removed during the call.  That lock is very
cheap and shouldn't affect any performance on ELS requests.
Providers can rely on the RCU lock to protect a session lookup as well.

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>

1 files changed, 56 insertions, 9 deletions

diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index c5a10f9..e2cd087 100644
--- a/drivers/scsi/libfc/fc_lport.c
+++ b/drivers/scsi/libfc/fc_lport.c
@@ -849,7 +849,7 @@ out:
 }
 
 /**
- * fc_lport_recv_req() - The generic lport request handler
+ * fc_lport_recv_els_req() - The generic lport ELS request handler
  * @lport: The local port that received the request
  * @fp:	   The request frame
  *
@@ -859,9 +859,9 @@ out:
  * Locking Note: This function should not be called with the lport
  *		 lock held becuase it will grab the lock.
  */
-static void fc_lport_recv_req(struct fc_lport *lport, struct fc_frame *fp)
+static void fc_lport_recv_els_req(struct fc_lport *lport,
+				  struct fc_frame *fp)
 {
-	struct fc_frame_header *fh = fc_frame_header_get(fp);
 	void (*recv)(struct fc_lport *, struct fc_frame *);
 
 	mutex_lock(&lport->lp_mutex);
@@ -873,8 +873,7 @@ static void fc_lport_recv_req(struct fc_lport *lport, struct fc_frame *fp)
 	 */
 	if (!lport->link_up)
 		fc_frame_free(fp);
-	else if (fh->fh_type == FC_TYPE_ELS &&
-		 fh->fh_r_ctl == FC_RCTL_ELS_REQ) {
+	else {
 		/*
 		 * Check opcode.
 		 */
@@ -903,14 +902,62 @@ static void fc_lport_recv_req(struct fc_lport *lport, struct fc_frame *fp)
 		}
 
 		recv(lport, fp);
-	} else {
-		FC_LPORT_DBG(lport, "dropping invalid frame (eof %x)\n",
-			     fr_eof(fp));
-		fc_frame_free(fp);
 	}
 	mutex_unlock(&lport->lp_mutex);
 }
 
+static int fc_lport_els_prli(struct fc_rport_priv *rdata, u32 spp_len,
+			     const struct fc_els_spp *spp_in,
+			     struct fc_els_spp *spp_out)
+{
+	return FC_SPP_RESP_INVL;
+}
+
+struct fc4_prov fc_lport_els_prov = {
+	.prli = fc_lport_els_prli,
+	.recv = fc_lport_recv_els_req,
+};
+
+/**
+ * fc_lport_recv_req() - The generic lport request handler
+ * @lport: The lport that received the request
+ * @fp: The frame the request is in
+ *
+ * Locking Note: This function should not be called with the lport
+ *		 lock held becuase it may grab the lock.
+ */
+static void fc_lport_recv_req(struct fc_lport *lport,
+			      struct fc_frame *fp)
+{
+	struct fc_frame_header *fh = fc_frame_header_get(fp);
+	struct fc_seq *sp = fr_seq(fp);
+	struct fc4_prov *prov;
+
+	/*
+	 * Use RCU read lock and module_lock to be sure module doesn't
+	 * deregister and get unloaded while we're calling it.
+	 * try_module_get() is inlined and accepts a NULL parameter.
+	 * Only ELSes and FCP target ops should come through here.
+	 * The locking is unfortunate, and a better scheme is being sought.
+	 */
+
+	rcu_read_lock();
+	if (fh->fh_type >= FC_FC4_PROV_SIZE)
+		goto drop;
+	prov = rcu_dereference(fc_passive_prov[fh->fh_type]);
+	if (!prov || !try_module_get(prov->module))
+		goto drop;
+	rcu_read_unlock();
+	prov->recv(lport, fp);
+	module_put(prov->module);
+	return;
+drop:
+	rcu_read_unlock();
+	FC_LPORT_DBG(lport, "dropping unexpected frame type %x\n", fh->fh_type);
+	fc_frame_free(fp);
+	lport->tt.exch_done(sp);
+}
+
 /**
  * fc_lport_reset() - Reset a local port
  * @lport: The local port which should be reset