[SCSI] fcoe: modifies fcoe_hostlist_lock uses as prep work to add shared offload EM

Modifies fcoe_hostlist_lock uses such that a new EM allocation in
fcoe_em_config and adding new fcoe_softc using fcoe_hostlist_add
are atomic, this is to ensure that a shared offload EM gets allocated
only once per eth device for its all lports.

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>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 18 insertions, 8 deletions

diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index ebf2e20370d7..86410b9a30c3 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -419,6 +419,8 @@ static int fcoe_shost_config(struct fc_lport *lp, struct Scsi_Host *shost,
  * fcoe_em_config() - allocates em for this lport
  * @lp: the port that em is to allocated for
  *
+ * Called with write fcoe_hostlist_lock held.
+ *
  * Returns : 0 on success
  */
 static inline int fcoe_em_config(struct fc_lport *lp)
@@ -607,6 +609,13 @@ static int fcoe_if_create(struct net_device *netdev)
                 goto out_lp_destroy;
         }
 
+        /*
+         * fcoe_em_alloc() and fcoe_hostlist_add() both
+         * need to be atomic under fcoe_hostlist_lock
+         * since fcoe_em_alloc() looks for an existing EM
+         * instance on host list updated by fcoe_hostlist_add().
+         */
+        write_lock(&fcoe_hostlist_lock);
         /* lport exch manager allocation */
         rc = fcoe_em_config(lp);
         if (rc) {
@@ -617,6 +626,7 @@ static int fcoe_if_create(struct net_device *netdev)
 
         /* add to lports list */
         fcoe_hostlist_add(lp);
+        write_unlock(&fcoe_hostlist_lock);
 
         lp->boot_time = jiffies;
 
@@ -1720,6 +1730,8 @@ int fcoe_reset(struct Scsi_Host *shost)
  * fcoe_hostlist_lookup_softc() - find the corresponding lport by a given device
  * @dev: this is currently ptr to net_device
  *
+ * Called with fcoe_hostlist_lock held.
+ *
  * Returns: NULL or the located fcoe_softc
  */
 static struct fcoe_softc *
@@ -1727,14 +1739,10 @@ fcoe_hostlist_lookup_softc(const struct net_device *dev)
 {
         struct fcoe_softc *fc;
 
-        read_lock(&fcoe_hostlist_lock);
         list_for_each_entry(fc, &fcoe_hostlist, list) {
-                if (fc->real_dev == dev) {
-                        read_unlock(&fcoe_hostlist_lock);
+                if (fc->real_dev == dev)
                         return fc;
-                }
         }
-        read_unlock(&fcoe_hostlist_lock);
         return NULL;
 }
 
@@ -1748,7 +1756,9 @@ struct fc_lport *fcoe_hostlist_lookup(const struct net_device *netdev)
 {
         struct fcoe_softc *fc;
 
+        read_lock(&fcoe_hostlist_lock);
         fc = fcoe_hostlist_lookup_softc(netdev);
+        read_unlock(&fcoe_hostlist_lock);
 
         return (fc) ? fc->ctlr.lp : NULL;
 }
@@ -1757,6 +1767,8 @@ struct fc_lport *fcoe_hostlist_lookup(const struct net_device *netdev)
  * fcoe_hostlist_add() - Add a lport to lports list
  * @lp: ptr to the fc_lport to be added
  *
+ * Called with write fcoe_hostlist_lock held.
+ *
  * Returns: 0 for success
  */
 int fcoe_hostlist_add(const struct fc_lport *lp)
@@ -1766,9 +1778,7 @@ int fcoe_hostlist_add(const struct fc_lport *lp)
         fc = fcoe_hostlist_lookup_softc(fcoe_netdev(lp));
         if (!fc) {
                 fc = lport_priv(lp);
-                write_lock_bh(&fcoe_hostlist_lock);
                 list_add_tail(&fc->list, &fcoe_hostlist);
-                write_unlock_bh(&fcoe_hostlist_lock);
         }
         return 0;
 }
@@ -1783,9 +1793,9 @@ int fcoe_hostlist_remove(const struct fc_lport *lp)
 {
         struct fcoe_softc *fc;
 
+        write_lock_bh(&fcoe_hostlist_lock);
         fc = fcoe_hostlist_lookup_softc(fcoe_netdev(lp));
         BUG_ON(!fc);
-        write_lock_bh(&fcoe_hostlist_lock);
         list_del(&fc->list);
         write_unlock_bh(&fcoe_hostlist_lock);