[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>

1 files changed, 2 insertions, 10 deletions

diff --git a/include/scsi/libfc.h b/include/scsi/libfc.h
index 042f4ade..b9e6c1c 100644
--- a/include/scsi/libfc.h
+++ b/include/scsi/libfc.h
@@ -68,9 +68,6 @@
 /*
  * FC HBA status
  */
-#define FC_PAUSE		    (1 << 1)
-#define FC_LINK_UP		    (1 << 0)
-
 enum fc_lport_state {
 	LPORT_ST_NONE = 0,
 	LPORT_ST_FLOGI,
@@ -603,7 +600,8 @@ struct fc_lport {
 
 	/* Operational Information */
 	struct libfc_function_template tt;
-	u16			link_status;
+	u8			link_up;
+	u8			qfull;
 	enum fc_lport_state	state;
 	unsigned long		boot_time;
 
@@ -704,12 +702,6 @@ void fc_linkup(struct fc_lport *);
 void fc_linkdown(struct fc_lport *);
 
 /*
- * Pause and unpause traffic.
- */
-void fc_pause(struct fc_lport *);
-void fc_unpause(struct fc_lport *);
-
-/*
  * Configure the local port.
  */
 int fc_lport_config(struct fc_lport *);