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>

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 2a7fd5afecca5328affe2cad44c6ada97e278485..47ebc7b1e143024ad90871c4d715c0f8d49ab5d9 100644 (file)
--- 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;
 }
 
 /**