rbd: introduce a per-device ordered workqueue

This is going to be used for re-registering watch requests and
exclusive-lock tasks: acquire/request lock, notify-acquired, release
lock, notify-released.  Some refactoring in the map/unmap paths was
necessary to give this workqueue a meaningful name: "rbdX-tasks".
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>

drivers/block/rbd.c

@@ -128,11 +128,8 @@ static int atomic_dec_return_safe(atomic_t *v)
 /*
  * An RBD device name will be "rbd#", where the "rbd" comes from
  * RBD_DRV_NAME above, and # is a unique integer identifier.
- * MAX_INT_FORMAT_WIDTH is used in ensuring DEV_NAME_LEN is big
- * enough to hold all possible device names.
  */
 #define DEV_NAME_LEN		32
-#define MAX_INT_FORMAT_WIDTH	((5 * sizeof (int)) / 2 + 1)
 
 /*
  * block device image metadata (in-memory version)
@@ -353,10 +350,12 @@ struct rbd_device {
 	struct ceph_object_id	header_oid;
 	struct ceph_object_locator header_oloc;
 
-	struct ceph_file_layout	layout;
+	struct ceph_file_layout	layout;		/* used for all rbd requests */
 
 	struct ceph_osd_linger_request *watch_handle;
 
+	struct workqueue_struct	*task_wq;
+
 	struct rbd_spec		*parent_spec;
 	u64			parent_overlap;
 	atomic_t		parent_ref;
@@ -3944,11 +3943,8 @@ static void rbd_spec_free(struct kref *kref)
 	kfree(spec);
 }
 
-static void rbd_dev_release(struct device *dev)
+static void rbd_dev_free(struct rbd_device *rbd_dev)
 {
-	struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
-	bool need_put = !!rbd_dev->opts;
-
 	ceph_oid_destroy(&rbd_dev->header_oid);
 	ceph_oloc_destroy(&rbd_dev->header_oloc);
 
@@ -3956,6 +3952,19 @@ static void rbd_dev_release(struct device *dev)
 	rbd_spec_put(rbd_dev->spec);
 	kfree(rbd_dev->opts);
 	kfree(rbd_dev);
+}
+
+static void rbd_dev_release(struct device *dev)
+{
+	struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+	bool need_put = !!rbd_dev->opts;
+
+	if (need_put) {
+		destroy_workqueue(rbd_dev->task_wq);
+		ida_simple_remove(&rbd_dev_id_ida, rbd_dev->dev_id);
+	}
+
+	rbd_dev_free(rbd_dev);
 
 	/*
 	 * This is racy, but way better than putting module outside of
@@ -3966,19 +3975,16 @@ static void rbd_dev_release(struct device *dev)
 		module_put(THIS_MODULE);
 }
 
-static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
-					 struct rbd_spec *spec,
-					 struct rbd_options *opts)
+static struct rbd_device *__rbd_dev_create(struct rbd_client *rbdc,
+					   struct rbd_spec *spec)
 {
 	struct rbd_device *rbd_dev;
 
-	rbd_dev = kzalloc(sizeof (*rbd_dev), GFP_KERNEL);
+	rbd_dev = kzalloc(sizeof(*rbd_dev), GFP_KERNEL);
 	if (!rbd_dev)
 		return NULL;
 
 	spin_lock_init(&rbd_dev->lock);
-	rbd_dev->flags = 0;
-	atomic_set(&rbd_dev->parent_ref, 0);
 	INIT_LIST_HEAD(&rbd_dev->node);
 	init_rwsem(&rbd_dev->header_rwsem);
 
@@ -3992,9 +3998,6 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
 
 	rbd_dev->rbd_client = rbdc;
 	rbd_dev->spec = spec;
-	rbd_dev->opts = opts;
-
-	/* Initialize the layout used for all rbd requests */
 
 	rbd_dev->layout.stripe_unit = 1 << RBD_MAX_OBJ_ORDER;
 	rbd_dev->layout.stripe_count = 1;
@@ -4002,15 +4005,48 @@ static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
 	rbd_dev->layout.pool_id = spec->pool_id;
 	RCU_INIT_POINTER(rbd_dev->layout.pool_ns, NULL);
 
-	/*
-	 * If this is a mapping rbd_dev (as opposed to a parent one),
-	 * pin our module.  We have a ref from do_rbd_add(), so use
-	 * __module_get().
+	return rbd_dev;
+}
+
+/*
+ * Create a mapping rbd_dev.
  */
-	if (rbd_dev->opts)
+static struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
+					 struct rbd_spec *spec,
+					 struct rbd_options *opts)
+{
+	struct rbd_device *rbd_dev;
+
+	rbd_dev = __rbd_dev_create(rbdc, spec);
+	if (!rbd_dev)
+		return NULL;
+
+	rbd_dev->opts = opts;
+
+	/* get an id and fill in device name */
+	rbd_dev->dev_id = ida_simple_get(&rbd_dev_id_ida, 0,
+					 minor_to_rbd_dev_id(1 << MINORBITS),
+					 GFP_KERNEL);
+	if (rbd_dev->dev_id < 0)
+		goto fail_rbd_dev;
+
+	sprintf(rbd_dev->name, RBD_DRV_NAME "%d", rbd_dev->dev_id);
+	rbd_dev->task_wq = alloc_ordered_workqueue("%s-tasks", WQ_MEM_RECLAIM,
+						   rbd_dev->name);
+	if (!rbd_dev->task_wq)
+		goto fail_dev_id;
+
+	/* we have a ref from do_rbd_add() */
 	__module_get(THIS_MODULE);
 
+	dout("%s rbd_dev %p dev_id %d\n", __func__, rbd_dev, rbd_dev->dev_id);
 	return rbd_dev;
+
+fail_dev_id:
+	ida_simple_remove(&rbd_dev_id_ida, rbd_dev->dev_id);
+fail_rbd_dev:
+	rbd_dev_free(rbd_dev);
+	return NULL;
 }
 
 static void rbd_dev_destroy(struct rbd_device *rbd_dev)
@@ -4645,46 +4681,6 @@ static int rbd_dev_header_info(struct rbd_device *rbd_dev)
 	return rbd_dev_v2_header_info(rbd_dev);
 }
 
-/*
- * Get a unique rbd identifier for the given new rbd_dev, and add
- * the rbd_dev to the global list.
- */
-static int rbd_dev_id_get(struct rbd_device *rbd_dev)
-{
-	int new_dev_id;
-
-	new_dev_id = ida_simple_get(&rbd_dev_id_ida,
-				    0, minor_to_rbd_dev_id(1 << MINORBITS),
-				    GFP_KERNEL);
-	if (new_dev_id < 0)
-		return new_dev_id;
-
-	rbd_dev->dev_id = new_dev_id;
-
-	spin_lock(&rbd_dev_list_lock);
-	list_add_tail(&rbd_dev->node, &rbd_dev_list);
-	spin_unlock(&rbd_dev_list_lock);
-
-	dout("rbd_dev %p given dev id %d\n", rbd_dev, rbd_dev->dev_id);
-
-	return 0;
-}
-
-/*
- * Remove an rbd_dev from the global list, and record that its
- * identifier is no longer in use.
- */
-static void rbd_dev_id_put(struct rbd_device *rbd_dev)
-{
-	spin_lock(&rbd_dev_list_lock);
-	list_del_init(&rbd_dev->node);
-	spin_unlock(&rbd_dev_list_lock);
-
-	ida_simple_remove(&rbd_dev_id_ida, rbd_dev->dev_id);
-
-	dout("rbd_dev %p released dev id %d\n", rbd_dev, rbd_dev->dev_id);
-}
-
 /*
  * Skips over white space at *buf, and updates *buf to point to the
  * first found non-space character (if any). Returns the length of
@@ -5077,8 +5073,7 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev, int depth)
 		goto out_err;
 	}
 
-	parent = rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec,
-				NULL);
+	parent = __rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec);
 	if (!parent) {
 		ret = -ENOMEM;
 		goto out_err;
@@ -5113,22 +5108,12 @@ static int rbd_dev_device_setup(struct rbd_device *rbd_dev)
 {
 	int ret;
 
-	/* Get an id and fill in device name. */
-
-	ret = rbd_dev_id_get(rbd_dev);
-	if (ret)
-		goto err_out_unlock;
-
-	BUILD_BUG_ON(DEV_NAME_LEN
-			< sizeof (RBD_DRV_NAME) + MAX_INT_FORMAT_WIDTH);
-	sprintf(rbd_dev->name, "%s%d", RBD_DRV_NAME, rbd_dev->dev_id);
-
 	/* Record our major and minor device numbers. */
 
 	if (!single_major) {
 		ret = register_blkdev(0, rbd_dev->name);
 		if (ret < 0)
-			goto err_out_id;
+			goto err_out_unlock;
 
 		rbd_dev->major = ret;
 		rbd_dev->minor = 0;
@@ -5160,6 +5145,10 @@ static int rbd_dev_device_setup(struct rbd_device *rbd_dev)
 	set_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
 	up_write(&rbd_dev->header_rwsem);
 
+	spin_lock(&rbd_dev_list_lock);
+	list_add_tail(&rbd_dev->node, &rbd_dev_list);
+	spin_unlock(&rbd_dev_list_lock);
+
 	add_disk(rbd_dev->disk);
 	pr_info("%s: added with size 0x%llx\n", rbd_dev->disk->disk_name,
 		(unsigned long long) rbd_dev->mapping.size);
@@ -5173,8 +5162,6 @@ static int rbd_dev_device_setup(struct rbd_device *rbd_dev)
 err_out_blkdev:
 	if (!single_major)
 		unregister_blkdev(rbd_dev->major, rbd_dev->name);
-err_out_id:
-	rbd_dev_id_put(rbd_dev);
 err_out_unlock:
 	up_write(&rbd_dev->header_rwsem);
 	return ret;
@@ -5406,12 +5393,16 @@ static ssize_t rbd_add_single_major(struct bus_type *bus,
 static void rbd_dev_device_release(struct rbd_device *rbd_dev)
 {
 	rbd_free_disk(rbd_dev);
+
+	spin_lock(&rbd_dev_list_lock);
+	list_del_init(&rbd_dev->node);
+	spin_unlock(&rbd_dev_list_lock);
+
 	clear_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
 	device_del(&rbd_dev->dev);
 	rbd_dev_mapping_clear(rbd_dev);
 	if (!single_major)
 		unregister_blkdev(rbd_dev->major, rbd_dev->name);
-	rbd_dev_id_put(rbd_dev);
 }
 
 static void rbd_dev_remove_parent(struct rbd_device *rbd_dev)