[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>

diff --git a/drivers/scsi/libsas/sas_port.c b/drivers/scsi/libsas/sas_port.c
index e6ac59c023f199393b10eed05bb086f34a12fee4..fe8b74c706d21d4449887070133db3294d1b50ac 100644 (file)
--- 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",