[SCSI] libfc: Enhanced exchange ID selection mechanism and fix related EMA selection logic.

Problem:

In case of exchange responder case, EMA selection was defaulted to the
last EMA from EMA list (lport.ema_list).  If exchange ID is selected
from offload pool and not setup DDP, resulting into incorrect
selection of EMA, and eventually dropping the packet because unable to
find exchange.

Fix:

Enhanced the exchange ID selection (depending upon request type and
exchange responder) Made necessary enhancement in EMA selection
algorithm.

Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 43 insertions, 21 deletions

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index a3d640289dcc..08bf5fa6afd4 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -2281,16 +2281,45 @@ void fc_exch_mgr_free(struct fc_lport *lport)
 EXPORT_SYMBOL(fc_exch_mgr_free);
 
 /**
+ * fc_find_ema() - Lookup and return appropriate Exchange Manager Anchor depending
+ * upon 'xid'.
+ * @f_ctl: f_ctl
+ * @lport: The local port the frame was received on
+ * @fh: The received frame header
+ */
+static struct fc_exch_mgr_anchor *fc_find_ema(u32 f_ctl,
+                                              struct fc_lport *lport,
+                                              struct fc_frame_header *fh)
+{
+        struct fc_exch_mgr_anchor *ema;
+        u16 xid;
+
+        if (f_ctl & FC_FC_EX_CTX)
+                xid = ntohs(fh->fh_ox_id);
+        else {
+                xid = ntohs(fh->fh_rx_id);
+                if (xid == FC_XID_UNKNOWN)
+                        return list_entry(lport->ema_list.prev,
+                                          typeof(*ema), ema_list);
+        }
+
+        list_for_each_entry(ema, &lport->ema_list, ema_list) {
+                if ((xid >= ema->mp->min_xid) &&
+                    (xid <= ema->mp->max_xid))
+                        return ema;
+        }
+        return NULL;
+}
+/**
  * fc_exch_recv() - Handler for received frames
  * @lport: The local port the frame was received on
- * @fp:    The received frame
+ * @fp: The received frame
  */
 void fc_exch_recv(struct fc_lport *lport, struct fc_frame *fp)
 {
         struct fc_frame_header *fh = fc_frame_header_get(fp);
         struct fc_exch_mgr_anchor *ema;
-        u32 f_ctl, found = 0;
-        u16 oxid;
+        u32 f_ctl;
 
         /* lport lock ? */
         if (!lport || lport->state == LPORT_ST_DISABLED) {
@@ -2301,24 +2330,17 @@ void fc_exch_recv(struct fc_lport *lport, struct fc_frame *fp)
         }
 
         f_ctl = ntoh24(fh->fh_f_ctl);
-        oxid = ntohs(fh->fh_ox_id);
-        if (f_ctl & FC_FC_EX_CTX) {
-                list_for_each_entry(ema, &lport->ema_list, ema_list) {
-                        if ((oxid >= ema->mp->min_xid) &&
-                            (oxid <= ema->mp->max_xid)) {
-                                found = 1;
-                                break;
-                        }
-                }
-
-                if (!found) {
-                        FC_LPORT_DBG(lport, "Received response for out "
-                                     "of range oxid:%hx\n", oxid);
-                        fc_frame_free(fp);
-                        return;
-                }
-        } else
-                ema = list_entry(lport->ema_list.prev, typeof(*ema), ema_list);
+        ema = fc_find_ema(f_ctl, lport, fh);
+        if (!ema) {
+                FC_LPORT_DBG(lport, "Unable to find Exchange Manager Anchor,"
+                                    "fc_ctl <0x%x>, xid <0x%x>\n",
+                                     f_ctl,
+                                     (f_ctl & FC_FC_EX_CTX) ?
+                                     ntohs(fh->fh_ox_id) :
+                                     ntohs(fh->fh_rx_id));
+                fc_frame_free(fp);
+                return;
+        }
 
         /*
          * If frame is marked invalid, just drop it.