[SCSI] libsas: fix sas_find_local_phy(), take phy references

In the direct-attached case this routine returns the phy on which this
device was first discovered.  Which is broken if we want to support
wide-targets, as this phy reference can become stale even though the
port is still active.

In the expander-attached case this routine tries to lookup the phy by
scanning the attached sas addresses of the parent expander, and BUG_ONs
if it can't find it.  However since eh and the libsas workqueue run
independently we can still be attempting device recovery via eh after
libsas has recorded the device as detached.  This is even easier to hit
now that eh is blocked while device domain rediscovery takes place, and
that libata is fed more timed out commands increasing the chances that
it will try to recover the ata device.

Arrange for dev->phy to always point to a last known good phy, it may be
stale after the port is torn down, but it will catch up for wide port
reconfigurations, and never be NULL.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

6 files changed, 55 insertions, 27 deletions

diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index 5fdb63ad94b7..92f7e78a096c 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -284,9 +284,10 @@ static int smp_ata_check_ready(struct ata_link *link)
         struct ata_port *ap = link->ap;
         struct domain_device *dev = ap->private_data;
         struct domain_device *ex_dev = dev->parent;
-        struct sas_phy *phy = sas_find_local_phy(dev);
+        struct sas_phy *phy = sas_get_local_phy(dev);
 
         res = sas_get_phy_attached_sas_addr(ex_dev, phy->number, addr);
+        sas_put_local_phy(phy);
         /* break the wait early if the expander is unreachable,
          * otherwise keep polling
          */
@@ -319,10 +320,10 @@ static int sas_ata_hard_reset(struct ata_link *link, unsigned int *class,
                               unsigned long deadline)
 {
         int ret = 0, res;
+        struct sas_phy *phy;
         struct ata_port *ap = link->ap;
         int (*check_ready)(struct ata_link *link);
         struct domain_device *dev = ap->private_data;
-        struct sas_phy *phy = sas_find_local_phy(dev);
         struct sas_internal *i = dev_to_sas_internal(dev);
 
         res = i->dft->lldd_I_T_nexus_reset(dev);
@@ -330,10 +331,12 @@ static int sas_ata_hard_reset(struct ata_link *link, unsigned int *class,
         if (res != TMF_RESP_FUNC_COMPLETE)
                 SAS_DPRINTK("%s: Unable to reset ata device?\n", __func__);
 
+        phy = sas_get_local_phy(dev);
         if (scsi_is_sas_phy_local(phy))
                 check_ready = local_ata_check_ready;
         else
                 check_ready = smp_ata_check_ready;
+        sas_put_local_phy(phy);
 
         ret = ata_wait_after_reset(link, deadline, check_ready);
         if (ret && ret != -EAGAIN)
diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index c56cc6400819..789b50861bb9 100644
--- a/drivers/scsi/libsas/sas_discover.c
+++ b/drivers/scsi/libsas/sas_discover.c
@@ -147,6 +147,7 @@ static int sas_get_port_device(struct asd_sas_port *port)
         memset(port->disc.eeds_a, 0, SAS_ADDR_SIZE);
         memset(port->disc.eeds_b, 0, SAS_ADDR_SIZE);
         port->disc.max_level = 0;
+        sas_device_set_phy(dev, port->port);
 
         dev->rphy = rphy;
 
@@ -234,6 +235,9 @@ void sas_free_device(struct kref *kref)
         if (dev->parent)
                 sas_put_device(dev->parent);
 
+        sas_port_put_phy(dev->phy);
+        dev->phy = NULL;
+
         /* remove the phys and ports, everything else should be gone */
         if (dev->dev_type == EDGE_DEV || dev->dev_type == FANOUT_DEV)
                 kfree(dev->ex_dev.ex_phy);
@@ -308,6 +312,26 @@ void sas_unregister_domain_devices(struct asd_sas_port *port)
 
 }
 
+void sas_device_set_phy(struct domain_device *dev, struct sas_port *port)
+{
+        struct sas_ha_struct *ha;
+        struct sas_phy *new_phy;
+
+        if (!dev)
+                return;
+
+        ha = dev->port->ha;
+        new_phy = sas_port_get_phy(port);
+
+        /* pin and record last seen phy */
+        spin_lock_irq(&ha->phy_port_lock);
+        if (new_phy) {
+                sas_port_put_phy(dev->phy);
+                dev->phy = new_phy;
+        }
+        spin_unlock_irq(&ha->phy_port_lock);
+}
+
 /* ---------- Discovery and Revalidation ---------- */
 
 /**
diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 6fb1f3afd1e0..68a80a00f73f 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -723,6 +723,7 @@ static struct domain_device *sas_ex_discover_end_dev(
                 }
         }
         sas_ex_get_linkrate(parent, child, phy);
+        sas_device_set_phy(child, phy->port);
 
 #ifdef CONFIG_SCSI_SAS_ATA
         if ((phy->attached_tproto & SAS_PROTOCOL_STP) || phy->attached_sata_dev) {
@@ -1810,7 +1811,7 @@ static void sas_unregister_devs_sas_addr(struct domain_device *parent,
 {
         struct expander_device *ex_dev = &parent->ex_dev;
         struct ex_phy *phy = &ex_dev->ex_phy[phy_id];
-        struct domain_device *child, *n;
+        struct domain_device *child, *n, *found = NULL;
         if (last) {
                 list_for_each_entry_safe(child, n,
                         &ex_dev->children, siblings) {
@@ -1822,6 +1823,7 @@ static void sas_unregister_devs_sas_addr(struct domain_device *parent,
                                         sas_unregister_ex_tree(parent->port, child);
                                 else
                                         sas_unregister_dev(parent->port, child);
+                                found = child;
                                 break;
                         }
                 }
@@ -1830,6 +1832,7 @@ static void sas_unregister_devs_sas_addr(struct domain_device *parent,
         memset(phy->attached_sas_addr, 0, SAS_ADDR_SIZE);
         if (phy->port) {
                 sas_port_delete_phy(phy->port, phy->phy);
+                sas_device_set_phy(found, phy->port);
                 if (phy->port->num_phys == 0)
                         sas_port_delete(phy->port);
                 phy->port = NULL;
diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
index a9a3bb94c1bc..c8febc71c40d 100644
--- a/drivers/scsi/libsas/sas_internal.h
+++ b/drivers/scsi/libsas/sas_internal.h
@@ -87,6 +87,7 @@ int sas_smp_phy_control(struct domain_device *dev, int phy_id,
                         enum phy_func phy_func, struct sas_phy_linkrates *);
 int sas_smp_get_phy_events(struct sas_phy *phy);
 
+void sas_device_set_phy(struct domain_device *dev, struct sas_port *port);
 struct domain_device *sas_find_dev_by_rphy(struct sas_rphy *rphy);
 struct domain_device *sas_ex_to_ata(struct domain_device *ex_dev, int phy_id);
 int sas_get_phy_attached_sas_addr(struct domain_device *dev, int phy_id,
diff --git a/drivers/scsi/libsas/sas_port.c b/drivers/scsi/libsas/sas_port.c
index 2980bde4e34a..31adcd1b4191 100644
--- a/drivers/scsi/libsas/sas_port.c
+++ b/drivers/scsi/libsas/sas_port.c
@@ -108,9 +108,6 @@ static void sas_form_port(struct asd_sas_phy *phy)
         port->num_phys++;
         port->phy_mask |= (1U << phy->id);
 
-        if (!port->phy)
-                port->phy = phy->phy;
-
         if (*(u64 *)port->attached_sas_addr == 0) {
                 port->class = phy->class;
                 memcpy(port->attached_sas_addr, phy->attached_sas_addr,
@@ -175,8 +172,10 @@ void sas_deform_port(struct asd_sas_phy *phy, int gone)
                 sas_unregister_domain_devices(port);
                 sas_port_delete(port->port);
                 port->port = NULL;
-        } else
+        } else {
                 sas_port_delete_phy(port->port, phy->phy);
+                sas_device_set_phy(dev, port->port);
+        }
 
         if (si->dft->lldd_port_deformed)
                 si->dft->lldd_port_deformed(phy);
diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index 5cc44fddfe95..94ef76316c31 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -439,30 +439,26 @@ static int sas_recover_I_T(struct domain_device *dev)
         return res;
 }
 
-/* Find the sas_phy that's attached to this device */
-struct sas_phy *sas_find_local_phy(struct domain_device *dev)
+/* take a reference on the last known good phy for this device */
+struct sas_phy *sas_get_local_phy(struct domain_device *dev)
 {
-        struct domain_device *pdev = dev->parent;
-        struct ex_phy *exphy = NULL;
-        int i;
+        struct sas_ha_struct *ha = dev->port->ha;
+        struct sas_phy *phy;
+        unsigned long flags;
 
-        /* Directly attached device */
-        if (!pdev)
-                return dev->port->phy;
+        /* a published domain device always has a valid phy, it may be
+         * stale, but it is never NULL
+         */
+        BUG_ON(!dev->phy);
 
-        /* Otherwise look in the expander */
-        for (i = 0; i < pdev->ex_dev.num_phys; i++)
-                if (!memcmp(dev->sas_addr,
-                            pdev->ex_dev.ex_phy[i].attached_sas_addr,
-                            SAS_ADDR_SIZE)) {
-                        exphy = &pdev->ex_dev.ex_phy[i];
-                        break;
-                }
+        spin_lock_irqsave(&ha->phy_port_lock, flags);
+        phy = dev->phy;
+        get_device(&phy->dev);
+        spin_unlock_irqrestore(&ha->phy_port_lock, flags);
 
-        BUG_ON(!exphy);
-        return exphy->phy;
+        return phy;
 }
-EXPORT_SYMBOL_GPL(sas_find_local_phy);
+EXPORT_SYMBOL_GPL(sas_get_local_phy);
 
 /* Attempt to send a LUN reset message to a device */
 int sas_eh_device_reset_handler(struct scsi_cmnd *cmd)
@@ -489,7 +485,7 @@ int sas_eh_device_reset_handler(struct scsi_cmnd *cmd)
 int sas_eh_bus_reset_handler(struct scsi_cmnd *cmd)
 {
         struct domain_device *dev = cmd_to_domain_dev(cmd);
-        struct sas_phy *phy = sas_find_local_phy(dev);
+        struct sas_phy *phy = sas_get_local_phy(dev);
         int res;
 
         res = sas_phy_reset(phy, 1);
@@ -497,6 +493,8 @@ int sas_eh_bus_reset_handler(struct scsi_cmnd *cmd)
                 SAS_DPRINTK("Bus reset of %s failed 0x%x\n",
                             kobject_name(&phy->dev.kobj),
                             res);
+        sas_put_local_phy(phy);
+
         if (res == TMF_RESP_FUNC_SUCC || res == TMF_RESP_FUNC_COMPLETE)
                 return SUCCESS;