2 files changed, 47 insertions, 6 deletions

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 3a80f96c2919..f87d85659359 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -65,15 +65,17 @@ struct workqueue_struct *ib_comp_unbound_wq;
 struct workqueue_struct *ib_wq;
 EXPORT_SYMBOL_GPL(ib_wq);
 
-/* The device_list and client_list contain devices and clients after their
+/* The device_list and clients contain devices and clients after their
  * registration has completed, and the devices and clients are removed
  * during unregistration. */
 static LIST_HEAD(device_list);
 static LIST_HEAD(client_list);
+#define CLIENT_REGISTERED XA_MARK_1
+static DEFINE_XARRAY_FLAGS(clients, XA_FLAGS_ALLOC);
 
 /*
  * device_mutex and lists_rwsem protect access to both device_list and
- * client_list.  device_mutex protects writer access by device and client
+ * clients.  device_mutex protects writer access by device and client
  * registration / de-registration.  lists_rwsem protects reader access to
  * these lists.  Iterators of these lists must lock it for read, while updates
  * to the lists must be done with a write lock. A special case is when the
@@ -564,6 +566,7 @@ int ib_register_device(struct ib_device *device, const char *name)
 {
         int ret;
         struct ib_client *client;
+        unsigned long index;
 
         setup_dma_device(device);
 
@@ -608,7 +611,7 @@ int ib_register_device(struct ib_device *device, const char *name)
 
         refcount_set(&device->refcount, 1);
 
-        list_for_each_entry(client, &client_list, list)
+        xa_for_each_marked (&clients, index, client, CLIENT_REGISTERED)
                 if (!add_client_context(device, client) && client->add)
                         client->add(device);
 
@@ -680,6 +683,32 @@ void ib_unregister_device(struct ib_device *device)
 }
 EXPORT_SYMBOL(ib_unregister_device);
 
+static int assign_client_id(struct ib_client *client)
+{
+        int ret;
+
+        /*
+         * The add/remove callbacks must be called in FIFO/LIFO order. To
+         * achieve this we assign client_ids so they are sorted in
+         * registration order, and retain a linked list we can reverse iterate
+         * to get the LIFO order. The extra linked list can go away if xarray
+         * learns to reverse iterate.
+         */
+        if (list_empty(&client_list))
+                client->client_id = 0;
+        else
+                client->client_id =
+                        list_last_entry(&client_list, struct ib_client, list)
+                                ->client_id;
+        ret = xa_alloc(&clients, &client->client_id, INT_MAX, client,
+                       GFP_KERNEL);
+        if (ret)
+                goto out;
+
+out:
+        return ret;
+}
+
 /**
  * ib_register_client - Register an IB client
  * @client:Client to register
@@ -696,15 +725,21 @@ EXPORT_SYMBOL(ib_unregister_device);
 int ib_register_client(struct ib_client *client)
 {
         struct ib_device *device;
+        int ret;
 
         mutex_lock(&device_mutex);
+        ret = assign_client_id(client);
+        if (ret) {
+                mutex_unlock(&device_mutex);
+                return ret;
+        }
 
         list_for_each_entry(device, &device_list, core_list)
                 if (!add_client_context(device, client) && client->add)
                         client->add(device);
 
         down_write(&lists_rwsem);
-        list_add_tail(&client->list, &client_list);
+        xa_set_mark(&clients, client->client_id, CLIENT_REGISTERED);
         up_write(&lists_rwsem);
 
         mutex_unlock(&device_mutex);
@@ -729,7 +764,7 @@ void ib_unregister_client(struct ib_client *client)
         mutex_lock(&device_mutex);
 
         down_write(&lists_rwsem);
-        list_del(&client->list);
+        xa_clear_mark(&clients, client->client_id, CLIENT_REGISTERED);
         up_write(&lists_rwsem);
 
         list_for_each_entry(device, &device_list, core_list) {
@@ -765,6 +800,10 @@ void ib_unregister_client(struct ib_client *client)
                 kfree(found_context);
         }
 
+        down_write(&lists_rwsem);
+        list_del(&client->list);
+        xa_erase(&clients, client->client_id);
+        up_write(&lists_rwsem);
         mutex_unlock(&device_mutex);
 }
 EXPORT_SYMBOL(ib_unregister_client);
@@ -1422,6 +1461,7 @@ static void __exit ib_core_cleanup(void)
         destroy_workqueue(ib_comp_wq);
         /* Make sure that any pending umem accounting work is done. */
         destroy_workqueue(ib_wq);
+        WARN_ON(!xa_empty(&clients));
 }
 
 MODULE_ALIAS_RDMA_NETLINK(RDMA_NL_LS, 4);
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index d8ba987e8b29..cc15820513cd 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -2610,7 +2610,7 @@ struct ib_device {
 };
 
 struct ib_client {
-        char  *name;
+        const char *name;
         void (*add)   (struct ib_device *);
         void (*remove)(struct ib_device *, void *client_data);
 
@@ -2637,6 +2637,7 @@ struct ib_client {
                         const struct sockaddr *addr,
                         void *client_data);
         struct list_head list;
+        u32 client_id;
 
         /* kverbs are not required by the client */
         u8 no_kverbs_req:1;