[SCSI] libsas: reuse the original port when hotplugging phys in wide ports

There's a hotplug problem in the way libsas allocates ports: it loops over the
available ports first trying to add to an existing for a wide port and
otherwise allocating the next free port.  This scheme only works if the port
array is packed from zero, which fails if a port gets hot unplugged and the
array becomes sparse.  In that case, a new port is formed even if there's a
wide port it should be part of.  Fix this by creating two loops over all the
ports:  the first to see if the phy should be part of a wide port and the
second to form a new port in an empty port slot.

Signed-off-by: Tom Peng <tom_peng@usish.com>
Signed-off-by: Jack Wang <jack_wang@usish.com>
Signed-off-by: Lindar Liu <lindar_liu@usish.com>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 15 insertions, 4 deletions

diff --git a/drivers/scsi/libsas/sas_port.c b/drivers/scsi/libsas/sas_port.c
index e6ac59c023f1..fe8b74c706d2 100644
--- a/drivers/scsi/libsas/sas_port.c
+++ b/drivers/scsi/libsas/sas_port.c
@@ -56,7 +56,7 @@ static void sas_form_port(struct asd_sas_phy *phy)
                 }
         }
 
-        /* find a port */
+        /* see if the phy should be part of a wide port */
         spin_lock_irqsave(&sas_ha->phy_port_lock, flags);
         for (i = 0; i < sas_ha->num_phys; i++) {
                 port = sas_ha->sas_port[i];
@@ -69,12 +69,23 @@ static void sas_form_port(struct asd_sas_phy *phy)
                         SAS_DPRINTK("phy%d matched wide port%d\n", phy->id,
                                     port->id);
                         break;
-                } else if (*(u64 *) port->sas_addr == 0 && port->num_phys==0) {
-                        memcpy(port->sas_addr, phy->sas_addr, SAS_ADDR_SIZE);
-                        break;
                 }
                 spin_unlock(&port->phy_list_lock);
         }
+        /* The phy does not match any existing port, create a new one */
+        if (i == sas_ha->num_phys) {
+                for (i = 0; i < sas_ha->num_phys; i++) {
+                        port = sas_ha->sas_port[i];
+                        spin_lock(&port->phy_list_lock);
+                        if (*(u64 *)port->sas_addr == 0
+                                && port->num_phys == 0) {
+                                memcpy(port->sas_addr, phy->sas_addr,
+                                        SAS_ADDR_SIZE);
+                                break;
+                        }
+                        spin_unlock(&port->phy_list_lock);
+                }
+        }
 
         if (i >= sas_ha->num_phys) {
                 printk(KERN_NOTICE "%s: couldn't find a free port, bug?\n",