target: simplify backend driver registration

Rewrite the backend driver registration based on what we did to the fabric
drivers:  introduce a read-only struct target_bakckend_ops that the driver
registers, which is then instanciate as a struct target_backend by the
core.  This allows the ops vector to be smaller and allows us to mark it
const.  At the same time the registration function can set up the
configfs attributes, avoiding the need to add additional boilerplate code
for that to the drivers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 54 insertions, 42 deletions

diff --git a/drivers/target/target_core_hba.c b/drivers/target/target_core_hba.c
index e6e496ff9546..62ea4e8e70a8 100644
--- a/drivers/target/target_core_hba.c
+++ b/drivers/target/target_core_hba.c
@@ -39,63 +39,75 @@
 
 #include "target_core_internal.h"
 
-static LIST_HEAD(subsystem_list);
-static DEFINE_MUTEX(subsystem_mutex);
+static LIST_HEAD(backend_list);
+static DEFINE_MUTEX(backend_mutex);
 
 static u32 hba_id_counter;
 
 static DEFINE_SPINLOCK(hba_lock);
 static LIST_HEAD(hba_list);
 
-int transport_subsystem_register(struct se_subsystem_api *sub_api)
-{
-	struct se_subsystem_api *s;
-
-	INIT_LIST_HEAD(&sub_api->sub_api_list);
 
-	mutex_lock(&subsystem_mutex);
-	list_for_each_entry(s, &subsystem_list, sub_api_list) {
-		if (!strcmp(s->name, sub_api->name)) {
-			pr_err("%p is already registered with"
-				" duplicate name %s, unable to process"
-				" request\n", s, s->name);
-			mutex_unlock(&subsystem_mutex);
+int transport_backend_register(const struct target_backend_ops *ops)
+{
+	struct target_backend *tb, *old;
+
+	tb = kzalloc(sizeof(*tb), GFP_KERNEL);
+	if (!tb)
+		return -ENOMEM;
+	tb->ops = ops;
+
+	mutex_lock(&backend_mutex);
+	list_for_each_entry(old, &backend_list, list) {
+		if (!strcmp(old->ops->name, ops->name)) {
+			pr_err("backend %s already registered.\n", ops->name);
+			mutex_unlock(&backend_mutex);
+			kfree(tb);
 			return -EEXIST;
 		}
 	}
-	list_add_tail(&sub_api->sub_api_list, &subsystem_list);
-	mutex_unlock(&subsystem_mutex);
+	target_setup_backend_cits(tb);
+	list_add_tail(&tb->list, &backend_list);
+	mutex_unlock(&backend_mutex);
 
-	pr_debug("TCM: Registered subsystem plugin: %s struct module:"
-			" %p\n", sub_api->name, sub_api->owner);
+	pr_debug("TCM: Registered subsystem plugin: %s struct module: %p\n",
+			ops->name, ops->owner);
 	return 0;
 }
-EXPORT_SYMBOL(transport_subsystem_register);
+EXPORT_SYMBOL(transport_backend_register);
 
-void transport_subsystem_release(struct se_subsystem_api *sub_api)
+void target_backend_unregister(const struct target_backend_ops *ops)
 {
-	mutex_lock(&subsystem_mutex);
-	list_del(&sub_api->sub_api_list);
-	mutex_unlock(&subsystem_mutex);
+	struct target_backend *tb;
+
+	mutex_lock(&backend_mutex);
+	list_for_each_entry(tb, &backend_list, list) {
+		if (tb->ops == ops) {
+			list_del(&tb->list);
+			kfree(tb);
+			break;
+		}
+	}
+	mutex_unlock(&backend_mutex);
 }
-EXPORT_SYMBOL(transport_subsystem_release);
+EXPORT_SYMBOL(target_backend_unregister);
 
-static struct se_subsystem_api *core_get_backend(const char *sub_name)
+static struct target_backend *core_get_backend(const char *name)
 {
-	struct se_subsystem_api *s;
+	struct target_backend *tb;
 
-	mutex_lock(&subsystem_mutex);
-	list_for_each_entry(s, &subsystem_list, sub_api_list) {
-		if (!strcmp(s->name, sub_name))
+	mutex_lock(&backend_mutex);
+	list_for_each_entry(tb, &backend_list, list) {
+		if (!strcmp(tb->ops->name, name))
 			goto found;
 	}
-	mutex_unlock(&subsystem_mutex);
+	mutex_unlock(&backend_mutex);
 	return NULL;
 found:
-	if (s->owner && !try_module_get(s->owner))
-		s = NULL;
-	mutex_unlock(&subsystem_mutex);
-	return s;
+	if (tb->ops->owner && !try_module_get(tb->ops->owner))
+		tb = NULL;
+	mutex_unlock(&backend_mutex);
+	return tb;
 }
 
 struct se_hba *
@@ -116,13 +128,13 @@ core_alloc_hba(const char *plugin_name, u32 plugin_dep_id, u32 hba_flags)
 	hba->hba_index = scsi_get_new_index(SCSI_INST_INDEX);
 	hba->hba_flags |= hba_flags;
 
-	hba->transport = core_get_backend(plugin_name);
-	if (!hba->transport) {
+	hba->backend = core_get_backend(plugin_name);
+	if (!hba->backend) {
 		ret = -EINVAL;
 		goto out_free_hba;
 	}
 
-	ret = hba->transport->attach_hba(hba, plugin_dep_id);
+	ret = hba->backend->ops->attach_hba(hba, plugin_dep_id);
 	if (ret < 0)
 		goto out_module_put;
 
@@ -137,8 +149,8 @@ core_alloc_hba(const char *plugin_name, u32 plugin_dep_id, u32 hba_flags)
 	return hba;
 
 out_module_put:
-	module_put(hba->transport->owner);
-	hba->transport = NULL;
+	module_put(hba->backend->ops->owner);
+	hba->backend = NULL;
 out_free_hba:
 	kfree(hba);
 	return ERR_PTR(ret);
@@ -149,7 +161,7 @@ core_delete_hba(struct se_hba *hba)
 {
 	WARN_ON(hba->dev_count);
 
-	hba->transport->detach_hba(hba);
+	hba->backend->ops->detach_hba(hba);
 
 	spin_lock(&hba_lock);
 	list_del(&hba->hba_node);
@@ -158,9 +170,9 @@ core_delete_hba(struct se_hba *hba)
 	pr_debug("CORE_HBA[%d] - Detached HBA from Generic Target"
 			" Core\n", hba->hba_id);
 
-	module_put(hba->transport->owner);
+	module_put(hba->backend->ops->owner);
 
-	hba->transport = NULL;
+	hba->backend = NULL;
 	kfree(hba);
 	return 0;
 }