libfc: Reduce exchange lock contention in fc_exch_recv_abts()

Reduce the time during which the exchange lock is held by allocating
a frame before obtaining the exchange lock.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>

1 files changed, 10 insertions, 8 deletions

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 2a7fd5afecca..47ebc7b1e143 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -1307,9 +1307,16 @@ static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)
 
         if (!ep)
                 goto reject;
+
+        fp = fc_frame_alloc(ep->lp, sizeof(*ap));
+        if (!fp)
+                goto free;
+
         spin_lock_bh(&ep->ex_lock);
         if (ep->esb_stat & ESB_ST_COMPLETE) {
                 spin_unlock_bh(&ep->ex_lock);
+
+                fc_frame_free(fp);
                 goto reject;
         }
         if (!(ep->esb_stat & ESB_ST_REC_QUAL)) {
@@ -1317,12 +1324,6 @@ static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)
                 fc_exch_hold(ep);               /* hold for REC_QUAL */
         }
         fc_exch_timer_set_locked(ep, ep->r_a_tov);
-
-        fp = fc_frame_alloc(ep->lp, sizeof(*ap));
-        if (!fp) {
-                spin_unlock_bh(&ep->ex_lock);
-                goto free;
-        }
         fh = fc_frame_header_get(fp);
         ap = fc_frame_payload_get(fp, sizeof(*ap));
         memset(ap, 0, sizeof(*ap));
@@ -1338,13 +1339,14 @@ static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)
         fc_seq_send_last(sp, fp, FC_RCTL_BA_ACC, FC_TYPE_BLS);
         ep->esb_stat |= ESB_ST_ABNORMAL;
         spin_unlock_bh(&ep->ex_lock);
+
+free:
         fc_frame_free(rx_fp);
         return;
 
 reject:
         fc_exch_send_ba_rjt(rx_fp, FC_BA_RJT_UNABLE, FC_BA_RJT_INV_XID);
-free:
-        fc_frame_free(rx_fp);
+        goto free;
 }
 
 /**