bdev: make module init asynchronous again

bdev_virtio requires us to do SCSI inquiry for
each device and wait for a response. It currently
polls inline for this response, taking up entire
reactor exclusively. Making it async would allow
other pollers to run while bdev_virtio still has
to wait.

Change-Id: Iefc88e0a2efb5b791ffe23b2e623b7c50d759084
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/375573
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>

include/spdk_internal/bdev.h

@@ -115,10 +115,10 @@ struct spdk_bdev_module_if {
 	void (*examine)(struct spdk_bdev *bdev);
 
 	/**
-	 * Count of bdev examinations in progress.  Used by generic bdev layer and must
+	 * Count of bdev inits/examinations in progress. Used by generic bdev
-	 * not be modified by bdev modules.
+	 * layer and must not be modified by bdev modules.
 	 */
-	uint32_t examine_in_progress;
+	uint32_t action_in_progress;
 
 	TAILQ_ENTRY(spdk_bdev_module_if) tailq;
 };
@@ -384,7 +384,7 @@ void spdk_vbdev_register(struct spdk_bdev *vbdev, struct spdk_bdev **base_bdevs,
 void spdk_vbdev_unregister(struct spdk_bdev *vbdev);
 
 void spdk_bdev_module_examine_done(struct spdk_bdev_module_if *module);
-
+void spdk_bdev_module_init_done(struct spdk_bdev_module_if *module);
 int spdk_bdev_module_claim_bdev(struct spdk_bdev *bdev, struct spdk_bdev_desc *desc,
 				struct spdk_bdev_module_if *module);
 void spdk_bdev_module_release_bdev(struct spdk_bdev *bdev);
@@ -451,7 +451,17 @@ spdk_bdev_io_from_ctx(void *ctx)
 	    spdk_bdev_module_list_add(&_name ## _if);                  				\
 	}
 
-#define SPDK_GET_BDEV_MODULE(name) &name ## _if
+#define SPDK_GET_BDEV_MODULE(name) (&name ## _if)
+
+/*
+ * Set module initialization to be asynchronous. After using this macro, the module
+ * initialization has to be explicitly finished by calling spdk_bdev_module_init_done().
+ */
+#define SPDK_BDEV_MODULE_ASYNC_INIT(name)							\
+	__attribute__((constructor)) static void name ## _async_init(void)			\
+	{											\
+		SPDK_GET_BDEV_MODULE(name)->action_in_progress = 1;				\
+	}
 
 /*
  * Modules are not required to use this macro.  It allows modules to reference the module with

lib/bdev/bdev.c

@@ -366,24 +366,53 @@ spdk_bdev_module_action_complete(void)
 	struct spdk_bdev_module_if *m;
 
 	/*
-	 * Check all bdev modules for an examinations in progress.  If any
+	 * Don't finish bdev subsystem initialization if
+	 * module pre-initialization is still in progress, or
+	 * the subsystem been already initialized.
+	 */
+	if (!g_bdev_mgr.module_init_complete || g_bdev_mgr.init_complete) {
+		return;
+	}
+
+	/*
+	 * Check all bdev modules for inits/examinations in progress. If any
 	 * exist, return immediately since we cannot finish bdev subsystem
 	 * initialization until all are completed.
 	 */
 	TAILQ_FOREACH(m, &g_bdev_mgr.bdev_modules, tailq) {
-		if (m->examine_in_progress > 0) {
+		if (m->action_in_progress > 0) {
 			return;
 		}
 	}
 
 	/*
 	 * Modules already finished initialization - now that all
-	 * the bdev moduless have finished their asynchronous I/O
+	 * the bdev modules have finished their asynchronous I/O
 	 * processing, the entire bdev layer can be marked as complete.
 	 */
 	spdk_bdev_init_complete(0);
 }
 
+static void
+spdk_bdev_module_action_done(struct spdk_bdev_module_if *module)
+{
+	assert(module->action_in_progress > 0);
+	module->action_in_progress--;
+	spdk_bdev_module_action_complete();
+}
+
+void
+spdk_bdev_module_init_done(struct spdk_bdev_module_if *module)
+{
+	spdk_bdev_module_action_done(module);
+}
+
+void
+spdk_bdev_module_examine_done(struct spdk_bdev_module_if *module)
+{
+	spdk_bdev_module_action_done(module);
+}
+
 static int
 spdk_bdev_modules_init(void)
 {
@@ -1433,7 +1462,7 @@ _spdk_bdev_register(struct spdk_bdev *bdev)
 
 	TAILQ_FOREACH(module, &g_bdev_mgr.bdev_modules, tailq) {
 		if (module->examine) {
-			module->examine_in_progress++;
+			module->action_in_progress++;
 			module->examine(bdev);
 		}
 	}
@@ -1510,24 +1539,6 @@ spdk_vbdev_unregister(struct spdk_bdev *vbdev)
 	spdk_bdev_unregister(vbdev);
 }
 
-void
-spdk_bdev_module_examine_done(struct spdk_bdev_module_if *module)
-{
-	assert(module->examine_in_progress > 0);
-	module->examine_in_progress--;
-
-	if (!g_bdev_mgr.module_init_complete || g_bdev_mgr.init_complete) {
-		/*
-		 * Don't finish bdev subsystem initialization if
-		 * module initialization is still in progress, or
-		 * the subsystem been already initialized.
-		 */
-		return;
-	}
-
-	spdk_bdev_module_action_complete();
-}
-
 int
 spdk_bdev_open(struct spdk_bdev *bdev, bool write, spdk_bdev_remove_cb_t remove_cb,
 	       void *remove_ctx, struct spdk_bdev_desc **_desc)