[SCSI] libfc: fix a circular locking warning during sending RRQ

Currently the fc_exch_rrq is called with fc_exch's ex_lock held.
The fc_exch_rrq allocates new exch and that requires taking
ex_lock again after EM lock. This locking order causes warning,
see more details on this warning at :-

 http://www.open-fcoe.org/pipermail/devel/2009-July/003251.html

This patch fixes this by dropping the ex_lock before calling
fc_exch_rrq().

The fc_exch_rrq needs to grab ex_lock lock again to schedule
RRQ retry and in the meanwhile fc_exch_reset could occur before
ex_lock is grabbed inside fc_exch_rrq. So to handle this case,
this patch adds additional check to detect fc_exch_reset after
ex_lock acquired and in case the fc_exch_reset occurred then
abandons the RRQ retry and releases the exch.

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, 15 insertions, 8 deletions

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 2bc22be5f849..145ab9ba55ea 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -415,9 +415,9 @@ static void fc_exch_timeout(struct work_struct *work)
         e_stat = ep->esb_stat;
         if (e_stat & ESB_ST_COMPLETE) {
                 ep->esb_stat = e_stat & ~ESB_ST_REC_QUAL;
+                spin_unlock_bh(&ep->ex_lock);
                 if (e_stat & ESB_ST_REC_QUAL)
                         fc_exch_rrq(ep);
-                spin_unlock_bh(&ep->ex_lock);
                 goto done;
         } else {
                 resp = ep->resp;
@@ -1624,14 +1624,14 @@ static void fc_exch_rrq(struct fc_exch *ep)
         struct fc_lport *lp;
         struct fc_els_rrq *rrq;
         struct fc_frame *fp;
-        struct fc_seq *rrq_sp;
         u32 did;
 
         lp = ep->lp;
 
         fp = fc_frame_alloc(lp, sizeof(*rrq));
         if (!fp)
-                return;
+                goto retry;
+
         rrq = fc_frame_payload_get(fp, sizeof(*rrq));
         memset(rrq, 0, sizeof(*rrq));
         rrq->rrq_cmd = ELS_RRQ;
@@ -1647,13 +1647,20 @@ static void fc_exch_rrq(struct fc_exch *ep)
                        fc_host_port_id(lp->host), FC_TYPE_ELS,
                        FC_FC_FIRST_SEQ | FC_FC_END_SEQ | FC_FC_SEQ_INIT, 0);
 
-        rrq_sp = fc_exch_seq_send(lp, fp, fc_exch_rrq_resp, NULL, ep,
-                                  lp->e_d_tov);
-        if (!rrq_sp) {
-                ep->esb_stat |= ESB_ST_REC_QUAL;
-                fc_exch_timer_set_locked(ep, ep->r_a_tov);
+        if (fc_exch_seq_send(lp, fp, fc_exch_rrq_resp, NULL, ep, lp->e_d_tov))
+                return;
+
+retry:
+        spin_lock_bh(&ep->ex_lock);
+        if (ep->state & (FC_EX_RST_CLEANUP | FC_EX_DONE)) {
+                spin_unlock_bh(&ep->ex_lock);
+                /* drop hold for rec qual */
+                fc_exch_release(ep);
                 return;
         }
+        ep->esb_stat |= ESB_ST_REC_QUAL;
+        fc_exch_timer_set_locked(ep, ep->r_a_tov);
+        spin_unlock_bh(&ep->ex_lock);
 }