[SCSI] libfc, fcoe: fixed locking issues with lport->lp_mutex around lport->link_status

The fcoe_xmit could call fc_pause in case the pending skb queue len is larger
than FCOE_MAX_QUEUE_DEPTH, the fc_pause was trying to grab lport->lp_muex to
change lport->link_status and that had these issues :-

1. The fcoe_xmit was getting called with bh disabled, thus causing
"BUG: scheduling while atomic" when grabbing lport->lp_muex with bh disabled.

2. fc_linkup and fc_linkdown function calls lport_enter function with
lport->lp_mutex held and these enter function in turn calls fcoe_xmit to send
lport related FC frame, e.g. fc_linkup => fc_lport_enter_flogi to send flogi
req. In this case grabbing the same lport->lp_mutex again in fc_puase from
fcoe_xmit would cause deadlock.

The lport->lp_mutex was used for setting FC_PAUSE in fcoe_xmit path but
FC_PAUSE bit was not used anywhere beside just setting and clear this
bit in lport->link_status, instead used a separate field qfull in fc_lport
to eliminate need for lport->lp_mutex to track pending queue full condition
and in turn avoid above described two locking issues.

Also added check for lp->qfull in fc_fcp_lport_queue_ready to trigger
SCSI_MLQUEUE_HOST_BUSY when lp->qfull is set to prevent more scsi-ml cmds
while lp->qfull is set.

This patch eliminated FC_LINK_UP and FC_PAUSE and instead used dedicated
fields in fc_lport for this, this simplified all related conditional
code.

Also removed fc_pause and fc_unpause functions and instead used newly added
lport->qfull directly in fcoe.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

2 files changed, 8 insertions, 32 deletions

diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index 404e63ff46b8..f440aaca39c2 100644
--- a/drivers/scsi/libfc/fc_fcp.c
+++ b/drivers/scsi/libfc/fc_fcp.c
@@ -1621,7 +1621,7 @@ out:
 static inline int fc_fcp_lport_queue_ready(struct fc_lport *lp)
 {
 	/* lock ? */
-	return (lp->state == LPORT_ST_READY) && (lp->link_status & FC_LINK_UP);
+	return (lp->state == LPORT_ST_READY) && lp->link_up && !lp->qfull;
 }
 
 /**
@@ -1890,7 +1890,7 @@ int fc_eh_abort(struct scsi_cmnd *sc_cmd)
 	lp = shost_priv(sc_cmd->device->host);
 	if (lp->state != LPORT_ST_READY)
 		return rc;
-	else if (!(lp->link_status & FC_LINK_UP))
+	else if (!lp->link_up)
 		return rc;
 
 	spin_lock_irqsave(lp->host->host_lock, flags);
diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index 5db223ce3b25..a6ab692f5f51 100644
--- a/drivers/scsi/libfc/fc_lport.c
+++ b/drivers/scsi/libfc/fc_lport.c
@@ -250,7 +250,7 @@ void fc_get_host_port_state(struct Scsi_Host *shost)
 {
 	struct fc_lport *lp = shost_priv(shost);
 
-	if ((lp->link_status & FC_LINK_UP) == FC_LINK_UP)
+	if (lp->link_up)
 		fc_host_port_state(shost) = FC_PORTSTATE_ONLINE;
 	else
 		fc_host_port_state(shost) = FC_PORTSTATE_OFFLINE;
@@ -577,8 +577,8 @@ void fc_linkup(struct fc_lport *lport)
 		       fc_host_port_id(lport->host));
 
 	mutex_lock(&lport->lp_mutex);
-	if ((lport->link_status & FC_LINK_UP) != FC_LINK_UP) {
-		lport->link_status |= FC_LINK_UP;
+	if (!lport->link_up) {
+		lport->link_up = 1;
 
 		if (lport->state == LPORT_ST_RESET)
 			fc_lport_enter_flogi(lport);
@@ -597,8 +597,8 @@ void fc_linkdown(struct fc_lport *lport)
 	FC_DEBUG_LPORT("Link is down for port (%6x)\n",
 		       fc_host_port_id(lport->host));
 
-	if ((lport->link_status & FC_LINK_UP) == FC_LINK_UP) {
-		lport->link_status &= ~(FC_LINK_UP);
+	if (lport->link_up) {
+		lport->link_up = 0;
 		fc_lport_enter_reset(lport);
 		lport->tt.fcp_cleanup(lport);
 	}
@@ -607,30 +607,6 @@ void fc_linkdown(struct fc_lport *lport)
 EXPORT_SYMBOL(fc_linkdown);
 
 /**
- * fc_pause - Pause the flow of frames
- * @lport: The lport to be paused
- */
-void fc_pause(struct fc_lport *lport)
-{
-	mutex_lock(&lport->lp_mutex);
-	lport->link_status |= FC_PAUSE;
-	mutex_unlock(&lport->lp_mutex);
-}
-EXPORT_SYMBOL(fc_pause);
-
-/**
- * fc_unpause - Unpause the flow of frames
- * @lport: The lport to be unpaused
- */
-void fc_unpause(struct fc_lport *lport)
-{
-	mutex_lock(&lport->lp_mutex);
-	lport->link_status &= ~(FC_PAUSE);
-	mutex_unlock(&lport->lp_mutex);
-}
-EXPORT_SYMBOL(fc_unpause);
-
-/**
  * fc_fabric_logoff - Logout of the fabric
  * @lport:	      fc_lport pointer to logoff the fabric
  *
@@ -977,7 +953,7 @@ static void fc_lport_enter_reset(struct fc_lport *lport)
 	fc_host_fabric_name(lport->host) = 0;
 	fc_host_port_id(lport->host) = 0;
 
-	if ((lport->link_status & FC_LINK_UP) == FC_LINK_UP)
+	if (lport->link_up)
 		fc_lport_enter_flogi(lport);
 }