[SCSI] libsas: fix domain_device leak

Arrange for the deallocation of a struct domain_device object when it no
longer has:
1/ any children
2/ references by any scsi_targets
3/ references by a lldd

The comment about domain_device lifetime in
Documentation/scsi/libsas.txt is stale as it appears mainline never had
a version of a struct domain_device that was registered as a kobject.
We now manage domain_device reference counts on behalf of external
agents.

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

6 files changed, 56 insertions, 41 deletions

diff --git a/Documentation/scsi/libsas.txt b/Documentation/scsi/libsas.txt
index aa54f54c4a50..3cc9c7843e15 100644
--- a/Documentation/scsi/libsas.txt
+++ b/Documentation/scsi/libsas.txt
@@ -398,21 +398,6 @@ struct sas_task {
         task_done -- callback when the task has finished execution
 };
 
-When an external entity, entity other than the LLDD or the
-SAS Layer, wants to work with a struct domain_device, it
-_must_ call kobject_get() when getting a handle on the
-device and kobject_put() when it is done with the device.
-
-This does two things:
-     A) implements proper kfree() for the device;
-     B) increments/decrements the kref for all players:
-     domain_device
-        all domain_device's ... (if past an expander)
-            port
-                host adapter
-                     pci device
-                         and up the ladder, etc.
-
 DISCOVERY
 ---------
 
diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
index 54a5199ceb56..4e649306ef4e 100644
--- a/drivers/scsi/libsas/sas_discover.c
+++ b/drivers/scsi/libsas/sas_discover.c
@@ -36,8 +36,6 @@
 
 void sas_init_dev(struct domain_device *dev)
 {
-        INIT_LIST_HEAD(&dev->siblings);
-        INIT_LIST_HEAD(&dev->dev_list_node);
         switch (dev->dev_type) {
         case SAS_END_DEV:
                 break;
@@ -73,14 +71,14 @@ static int sas_get_port_device(struct asd_sas_port *port)
         struct sas_rphy *rphy;
         struct domain_device *dev;
 
-        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+        dev = sas_alloc_device();
         if (!dev)
                 return -ENOMEM;
 
         spin_lock_irqsave(&port->phy_list_lock, flags);
         if (list_empty(&port->phy_list)) {
                 spin_unlock_irqrestore(&port->phy_list_lock, flags);
-                kfree(dev);
+                sas_put_device(dev);
                 return -ENODEV;
         }
         phy = container_of(port->phy_list.next, struct asd_sas_phy, port_phy_el);
@@ -130,7 +128,7 @@ static int sas_get_port_device(struct asd_sas_port *port)
         }
 
         if (!rphy) {
-                kfree(dev);
+                sas_put_device(dev);
                 return -ENODEV;
         }
         rphy->identify.phy_identifier = phy->phy->identify.phy_identifier;
@@ -173,6 +171,7 @@ int sas_notify_lldd_dev_found(struct domain_device *dev)
                                dev_name(sas_ha->dev),
                                SAS_ADDR(dev->sas_addr), res);
                 }
+                kref_get(&dev->kref);
         }
         return res;
 }
@@ -184,8 +183,10 @@ void sas_notify_lldd_dev_gone(struct domain_device *dev)
         struct Scsi_Host *shost = sas_ha->core.shost;
         struct sas_internal *i = to_sas_internal(shost->transportt);
 
-        if (i->dft->lldd_dev_gone)
+        if (i->dft->lldd_dev_gone) {
                 i->dft->lldd_dev_gone(dev);
+                sas_put_device(dev);
+        }
 }
 
 /* ---------- Common/dispatchers ---------- */
@@ -219,6 +220,20 @@ out_err2:
 
 /* ---------- Device registration and unregistration ---------- */
 
+void sas_free_device(struct kref *kref)
+{
+        struct domain_device *dev = container_of(kref, typeof(*dev), kref);
+
+        if (dev->parent)
+                sas_put_device(dev->parent);
+
+        /* 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);
+
+        kfree(dev);
+}
+
 static void sas_unregister_common_dev(struct asd_sas_port *port, struct domain_device *dev)
 {
         sas_notify_lldd_dev_gone(dev);
@@ -230,6 +245,8 @@ static void sas_unregister_common_dev(struct asd_sas_port *port, struct domain_d
         spin_lock_irq(&port->dev_list_lock);
         list_del_init(&dev->dev_list_node);
         spin_unlock_irq(&port->dev_list_lock);
+
+        sas_put_device(dev);
 }
 
 void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev)
@@ -239,11 +256,6 @@ void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev)
                 sas_rphy_delete(dev->rphy);
                 dev->rphy = NULL;
         }
-        if (dev->dev_type == EDGE_DEV || dev->dev_type == FANOUT_DEV) {
-                /* remove the phys and ports, everything else should be gone */
-                kfree(dev->ex_dev.ex_phy);
-                dev->ex_dev.ex_phy = NULL;
-        }
         sas_unregister_common_dev(port, dev);
 }
 
@@ -322,7 +334,7 @@ static void sas_discover_domain(struct work_struct *work)
                 list_del_init(&dev->dev_list_node);
                 spin_unlock_irq(&port->dev_list_lock);
 
-                kfree(dev); /* not kobject_register-ed yet */
+                sas_put_device(dev);
                 port->port_dev = NULL;
         }
 
diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 1b831c55ec6e..15d2239a378b 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -657,10 +657,11 @@ static struct domain_device *sas_ex_discover_end_dev(
         if (phy->attached_sata_host || phy->attached_sata_ps)
                 return NULL;
 
-        child = kzalloc(sizeof(*child), GFP_KERNEL);
+        child = sas_alloc_device();
         if (!child)
                 return NULL;
 
+        kref_get(&parent->kref);
         child->parent = parent;
         child->port   = parent->port;
         child->iproto = phy->attached_iproto;
@@ -762,7 +763,7 @@ static struct domain_device *sas_ex_discover_end_dev(
         sas_port_delete(phy->port);
  out_err:
         phy->port = NULL;
-        kfree(child);
+        sas_put_device(child);
         return NULL;
 }
 
@@ -809,7 +810,7 @@ static struct domain_device *sas_ex_discover_expander(
                             phy->attached_phy_id);
                 return NULL;
         }
-        child = kzalloc(sizeof(*child), GFP_KERNEL);
+        child = sas_alloc_device();
         if (!child)
                 return NULL;
 
@@ -835,6 +836,7 @@ static struct domain_device *sas_ex_discover_expander(
         child->rphy = rphy;
         edev = rphy_to_expander_device(rphy);
         child->dev_type = phy->attached_dev_type;
+        kref_get(&parent->kref);
         child->parent = parent;
         child->port = port;
         child->iproto = phy->attached_iproto;
@@ -858,7 +860,7 @@ static struct domain_device *sas_ex_discover_expander(
                 spin_lock_irq(&parent->port->dev_list_lock);
                 list_del(&child->dev_list_node);
                 spin_unlock_irq(&parent->port->dev_list_lock);
-                kfree(child);
+                sas_put_device(child);
                 return NULL;
         }
         list_add_tail(&child->siblings, &parent->ex_dev.children);
diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
index 14e21b5fb8ba..0d43408196f9 100644
--- a/drivers/scsi/libsas/sas_internal.h
+++ b/drivers/scsi/libsas/sas_internal.h
@@ -76,6 +76,8 @@ struct domain_device *sas_find_dev_by_rphy(struct sas_rphy *rphy);
 
 void sas_hae_reset(struct work_struct *work);
 
+void sas_free_device(struct kref *kref);
+
 #ifdef CONFIG_SCSI_SAS_HOST_SMP
 extern int sas_smp_host_handler(struct Scsi_Host *shost, struct request *req,
                                 struct request *rsp);
@@ -161,4 +163,21 @@ static inline void sas_add_parent_port(struct domain_device *dev, int phy_id)
         sas_port_add_phy(ex->parent_port, ex_phy->phy);
 }
 
+static inline struct domain_device *sas_alloc_device(void)
+{
+        struct domain_device *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+
+        if (dev) {
+                INIT_LIST_HEAD(&dev->siblings);
+                INIT_LIST_HEAD(&dev->dev_list_node);
+                kref_init(&dev->kref);
+        }
+        return dev;
+}
+
+static inline void sas_put_device(struct domain_device *dev)
+{
+        kref_put(&dev->kref, sas_free_device);
+}
+
 #endif /* _SAS_INTERNAL_H_ */
diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index e95e5e17bd88..2a163c73fd8b 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -737,16 +737,10 @@ struct domain_device *sas_find_dev_by_rphy(struct sas_rphy *rphy)
         return found_dev;
 }
 
-static inline struct domain_device *sas_find_target(struct scsi_target *starget)
-{
-        struct sas_rphy *rphy = dev_to_rphy(starget->dev.parent);
-
-        return sas_find_dev_by_rphy(rphy);
-}
-
 int sas_target_alloc(struct scsi_target *starget)
 {
-        struct domain_device *found_dev = sas_find_target(starget);
+        struct sas_rphy *rphy = dev_to_rphy(starget->dev.parent);
+        struct domain_device *found_dev = sas_find_dev_by_rphy(rphy);
         int res;
 
         if (!found_dev)
@@ -758,6 +752,7 @@ int sas_target_alloc(struct scsi_target *starget)
                         return res;
         }
 
+        kref_get(&found_dev->kref);
         starget->hostdata = found_dev;
         return 0;
 }
@@ -1047,7 +1042,7 @@ int sas_slave_alloc(struct scsi_device *scsi_dev)
 
 void sas_target_destroy(struct scsi_target *starget)
 {
-        struct domain_device *found_dev = sas_find_target(starget);
+        struct domain_device *found_dev = starget->hostdata;
 
         if (!found_dev)
                 return;
@@ -1055,7 +1050,8 @@ void sas_target_destroy(struct scsi_target *starget)
         if (dev_is_sata(found_dev))
                 ata_sas_port_destroy(found_dev->sata_dev.ap);
 
-        return;
+        starget->hostdata = NULL;
+        sas_put_device(found_dev);
 }
 
 static void sas_parse_addr(u8 *sas_addr, const char *p)
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index 2b14348336d6..7ecb5c1c0851 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -206,6 +206,7 @@ struct domain_device {
 
         void *lldd_dev;
         int gone;
+        struct kref kref;
 };
 
 struct sas_discovery_event {