1 files changed, 263 insertions, 174 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7044ef76a19d..99a0dd58602e 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -53,35 +53,45 @@ struct nbd_sock {
 	int fallback_index;
 };
 
+struct recv_thread_args {
+	struct work_struct work;
+	struct nbd_device *nbd;
+	int index;
+};
+
 #define NBD_TIMEDOUT			0
 #define NBD_DISCONNECT_REQUESTED	1
 #define NBD_DISCONNECTED		2
-#define NBD_RUNNING			3
+#define NBD_HAS_PID_FILE		3
 
-struct nbd_device {
+struct nbd_config {
 	u32 flags;
 	unsigned long runtime_flags;
-	struct nbd_sock **socks;
-	int magic;
-
-	struct blk_mq_tag_set tag_set;
 
-	struct mutex config_lock;
-	struct gendisk *disk;
+	struct nbd_sock **socks;
 	int num_connections;
+
 	atomic_t recv_threads;
 	wait_queue_head_t recv_wq;
 	loff_t blksize;
 	loff_t bytesize;
-
-	struct task_struct *task_recv;
-	struct task_struct *task_setup;
-
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 	struct dentry *dbg_dir;
 #endif
 };
 
+struct nbd_device {
+	struct blk_mq_tag_set tag_set;
+
+	refcount_t config_refs;
+	struct nbd_config *config;
+	struct mutex config_lock;
+	struct gendisk *disk;
+
+	struct task_struct *task_recv;
+	struct task_struct *task_setup;
+};
+
 struct nbd_cmd {
 	struct nbd_device *nbd;
 	int index;
@@ -103,7 +113,7 @@ static int part_shift;
 
 static int nbd_dev_dbg_init(struct nbd_device *nbd);
 static void nbd_dev_dbg_close(struct nbd_device *nbd);
-
+static void nbd_config_put(struct nbd_device *nbd);
 
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
 {
@@ -127,6 +137,20 @@ static const char *nbdcmd_to_ascii(int cmd)
 	return "invalid";
 }
 
+static ssize_t pid_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
+
+	return sprintf(buf, "%d\n", task_pid_nr(nbd->task_recv));
+}
+
+static struct device_attribute pid_attr = {
+	.attr = { .name = "pid", .mode = S_IRUGO},
+	.show = pid_show,
+};
+
 static void nbd_mark_nsock_dead(struct nbd_sock *nsock)
 {
 	if (!nsock->dead)
@@ -138,28 +162,32 @@ static void nbd_mark_nsock_dead(struct nbd_sock *nsock)
 
 static int nbd_size_clear(struct nbd_device *nbd, struct block_device *bdev)
 {
-	if (bdev->bd_openers <= 1)
-		bd_set_size(bdev, 0);
-	set_capacity(nbd->disk, 0);
-	kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
+	if (nbd->config->bytesize) {
+		if (bdev->bd_openers <= 1)
+			bd_set_size(bdev, 0);
+		set_capacity(nbd->disk, 0);
+		kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
+	}
 
 	return 0;
 }
 
 static void nbd_size_update(struct nbd_device *nbd, struct block_device *bdev)
 {
-	blk_queue_logical_block_size(nbd->disk->queue, nbd->blksize);
-	blk_queue_physical_block_size(nbd->disk->queue, nbd->blksize);
-	bd_set_size(bdev, nbd->bytesize);
-	set_capacity(nbd->disk, nbd->bytesize >> 9);
+	struct nbd_config *config = nbd->config;
+	blk_queue_logical_block_size(nbd->disk->queue, config->blksize);
+	blk_queue_physical_block_size(nbd->disk->queue, config->blksize);
+	bd_set_size(bdev, config->bytesize);
+	set_capacity(nbd->disk, config->bytesize >> 9);
 	kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
 }
 
 static void nbd_size_set(struct nbd_device *nbd, struct block_device *bdev,
 			loff_t blocksize, loff_t nr_blocks)
 {
-	nbd->blksize = blocksize;
-	nbd->bytesize = blocksize * nr_blocks;
+	struct nbd_config *config = nbd->config;
+	config->blksize = blocksize;
+	config->bytesize = blocksize * nr_blocks;
 	if (nbd_is_connected(nbd))
 		nbd_size_update(nbd, bdev);
 }
@@ -181,17 +209,19 @@ static void nbd_end_request(struct nbd_cmd *cmd)
  */
 static void sock_shutdown(struct nbd_device *nbd)
 {
+	struct nbd_config *config = nbd->config;
 	int i;
 
-	if (nbd->num_connections == 0)
+	if (config->num_connections == 0)
 		return;
-	if (test_and_set_bit(NBD_DISCONNECTED, &nbd->runtime_flags))
+	if (test_and_set_bit(NBD_DISCONNECTED, &config->runtime_flags))
 		return;
 
-	for (i = 0; i < nbd->num_connections; i++) {
-		struct nbd_sock *nsock = nbd->socks[i];
+	for (i = 0; i < config->num_connections; i++) {
+		struct nbd_sock *nsock = config->socks[i];
 		mutex_lock(&nsock->tx_lock);
 		kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
+		nbd_mark_nsock_dead(nsock);
 		mutex_unlock(&nsock->tx_lock);
 	}
 	dev_warn(disk_to_dev(nbd->disk), "shutting down sockets\n");
@@ -202,38 +232,43 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
 {
 	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
 	struct nbd_device *nbd = cmd->nbd;
+	struct nbd_config *config;
+
+	if (!refcount_inc_not_zero(&nbd->config_refs)) {
+		req->errors = -EIO;
+		return BLK_EH_HANDLED;
+	}
 
-	if (nbd->num_connections > 1) {
+	config = nbd->config;
+
+	if (config->num_connections > 1) {
 		dev_err_ratelimited(nbd_to_dev(nbd),
 				    "Connection timed out, retrying\n");
-		mutex_lock(&nbd->config_lock);
 		/*
 		 * Hooray we have more connections, requeue this IO, the submit
 		 * path will put it on a real connection.
 		 */
-		if (nbd->socks && nbd->num_connections > 1) {
-			if (cmd->index < nbd->num_connections) {
+		if (config->socks && config->num_connections > 1) {
+			if (cmd->index < config->num_connections) {
 				struct nbd_sock *nsock =
-					nbd->socks[cmd->index];
+					config->socks[cmd->index];
 				mutex_lock(&nsock->tx_lock);
 				nbd_mark_nsock_dead(nsock);
 				mutex_unlock(&nsock->tx_lock);
 			}
-			mutex_unlock(&nbd->config_lock);
 			blk_mq_requeue_request(req, true);
+			nbd_config_put(nbd);
 			return BLK_EH_NOT_HANDLED;
 		}
-		mutex_unlock(&nbd->config_lock);
 	} else {
 		dev_err_ratelimited(nbd_to_dev(nbd),
 				    "Connection timed out\n");
 	}
-	set_bit(NBD_TIMEDOUT, &nbd->runtime_flags);
+	set_bit(NBD_TIMEDOUT, &config->runtime_flags);
 	req->errors = -EIO;
-
-	mutex_lock(&nbd->config_lock);
 	sock_shutdown(nbd);
-	mutex_unlock(&nbd->config_lock);
+	nbd_config_put(nbd);
+
 	return BLK_EH_HANDLED;
 }
 
@@ -243,7 +278,8 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
 static int sock_xmit(struct nbd_device *nbd, int index, int send,
 		     struct iov_iter *iter, int msg_flags, int *sent)
 {
-	struct socket *sock = nbd->socks[index]->sock;
+	struct nbd_config *config = nbd->config;
+	struct socket *sock = config->socks[index]->sock;
 	int result;
 	struct msghdr msg;
 	unsigned long pflags = current->flags;
@@ -289,7 +325,8 @@ static int sock_xmit(struct nbd_device *nbd, int index, int send,
 static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
-	struct nbd_sock *nsock = nbd->socks[index];
+	struct nbd_config *config = nbd->config;
+	struct nbd_sock *nsock = config->socks[index];
 	int result;
 	struct nbd_request request = {.magic = htonl(NBD_REQUEST_MAGIC)};
 	struct kvec iov = {.iov_base = &request, .iov_len = sizeof(request)};
@@ -320,7 +357,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
 	}
 
 	if (rq_data_dir(req) == WRITE &&
-	    (nbd->flags & NBD_FLAG_READ_ONLY)) {
+	    (config->flags & NBD_FLAG_READ_ONLY)) {
 		dev_err_ratelimited(disk_to_dev(nbd->disk),
 				    "Write on read-only\n");
 		return -EIO;
@@ -426,15 +463,16 @@ out:
 	return 0;
 }
 
-static int nbd_disconnected(struct nbd_device *nbd)
+static int nbd_disconnected(struct nbd_config *config)
 {
-	return test_bit(NBD_DISCONNECTED, &nbd->runtime_flags) ||
-		test_bit(NBD_DISCONNECT_REQUESTED, &nbd->runtime_flags);
+	return test_bit(NBD_DISCONNECTED, &config->runtime_flags) ||
+		test_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags);
 }
 
 /* NULL returned = something went wrong, inform userspace */
 static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
 {
+	struct nbd_config *config = nbd->config;
 	int result;
 	struct nbd_reply reply;
 	struct nbd_cmd *cmd;
@@ -448,7 +486,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
 	iov_iter_kvec(&to, READ | ITER_KVEC, &iov, 1, sizeof(reply));
 	result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL);
 	if (result <= 0) {
-		if (!nbd_disconnected(nbd))
+		if (!nbd_disconnected(config))
 			dev_err(disk_to_dev(nbd->disk),
 				"Receive control failed (result %d)\n", result);
 		return ERR_PTR(result);
@@ -498,8 +536,8 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
 				 * and let the timeout stuff handle resubmitting
 				 * this request onto another connection.
 				 */
-				if (nbd_disconnected(nbd) ||
-				    nbd->num_connections <= 1) {
+				if (nbd_disconnected(config) ||
+				    config->num_connections <= 1) {
 					req->errors = -EIO;
 					return cmd;
 				}
@@ -515,40 +553,20 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
 	return cmd;
 }
 
-static ssize_t pid_show(struct device *dev,
-			struct device_attribute *attr, char *buf)
-{
-	struct gendisk *disk = dev_to_disk(dev);
-	struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
-
-	return sprintf(buf, "%d\n", task_pid_nr(nbd->task_recv));
-}
-
-static struct device_attribute pid_attr = {
-	.attr = { .name = "pid", .mode = S_IRUGO},
-	.show = pid_show,
-};
-
-struct recv_thread_args {
-	struct work_struct work;
-	struct nbd_device *nbd;
-	int index;
-};
-
 static void recv_work(struct work_struct *work)
 {
 	struct recv_thread_args *args = container_of(work,
 						     struct recv_thread_args,
 						     work);
 	struct nbd_device *nbd = args->nbd;
+	struct nbd_config *config = nbd->config;
 	struct nbd_cmd *cmd;
 	int ret = 0;
 
-	BUG_ON(nbd->magic != NBD_MAGIC);
 	while (1) {
 		cmd = nbd_read_stat(nbd, args->index);
 		if (IS_ERR(cmd)) {
-			struct nbd_sock *nsock = nbd->socks[args->index];
+			struct nbd_sock *nsock = config->socks[args->index];
 
 			mutex_lock(&nsock->tx_lock);
 			nbd_mark_nsock_dead(nsock);
@@ -559,8 +577,10 @@ static void recv_work(struct work_struct *work)
 
 		nbd_end_request(cmd);
 	}
-	atomic_dec(&nbd->recv_threads);
-	wake_up(&nbd->recv_wq);
+	atomic_dec(&config->recv_threads);
+	wake_up(&config->recv_wq);
+	nbd_config_put(nbd);
+	kfree(args);
 }
 
 static void nbd_clear_req(struct request *req, void *data, bool reserved)
@@ -576,39 +596,38 @@ static void nbd_clear_req(struct request *req, void *data, bool reserved)
 
 static void nbd_clear_que(struct nbd_device *nbd)
 {
-	BUG_ON(nbd->magic != NBD_MAGIC);
-
 	blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL);
 	dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n");
 }
 
 static int find_fallback(struct nbd_device *nbd, int index)
 {
+	struct nbd_config *config = nbd->config;
 	int new_index = -1;
-	struct nbd_sock *nsock = nbd->socks[index];
+	struct nbd_sock *nsock = config->socks[index];
 	int fallback = nsock->fallback_index;
 
-	if (test_bit(NBD_DISCONNECTED, &nbd->runtime_flags))
+	if (test_bit(NBD_DISCONNECTED, &config->runtime_flags))
 		return new_index;
 
-	if (nbd->num_connections <= 1) {
+	if (config->num_connections <= 1) {
 		dev_err_ratelimited(disk_to_dev(nbd->disk),
 				    "Attempted send on invalid socket\n");
 		return new_index;
 	}
 
-	if (fallback >= 0 && fallback < nbd->num_connections &&
-	    !nbd->socks[fallback]->dead)
+	if (fallback >= 0 && fallback < config->num_connections &&
+	    !config->socks[fallback]->dead)
 		return fallback;
 
 	if (nsock->fallback_index < 0 ||
-	    nsock->fallback_index >= nbd->num_connections ||
-	    nbd->socks[nsock->fallback_index]->dead) {
+	    nsock->fallback_index >= config->num_connections ||
+	    config->socks[nsock->fallback_index]->dead) {
 		int i;
-		for (i = 0; i < nbd->num_connections; i++) {
+		for (i = 0; i < config->num_connections; i++) {
 			if (i == index)
 				continue;
-			if (!nbd->socks[i]->dead) {
+			if (!config->socks[i]->dead) {
 				new_index = i;
 				break;
 			}
@@ -628,23 +647,34 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
 	struct nbd_device *nbd = cmd->nbd;
+	struct nbd_config *config;
 	struct nbd_sock *nsock;
 	int ret;
 
-	if (index >= nbd->num_connections) {
+	if (!refcount_inc_not_zero(&nbd->config_refs)) {
+		dev_err_ratelimited(disk_to_dev(nbd->disk),
+				    "Socks array is empty\n");
+		return -EINVAL;
+	}
+	config = nbd->config;
+
+	if (index >= config->num_connections) {
 		dev_err_ratelimited(disk_to_dev(nbd->disk),
 				    "Attempted send on invalid socket\n");
+		nbd_config_put(nbd);
 		return -EINVAL;
 	}
 	req->errors = 0;
 again:
-	nsock = nbd->socks[index];
+	nsock = config->socks[index];
 	mutex_lock(&nsock->tx_lock);
 	if (nsock->dead) {
 		index = find_fallback(nbd, index);
+		if (index < 0) {
+			ret = -EIO;
+			goto out;
+		}
 		mutex_unlock(&nsock->tx_lock);
-		if (index < 0)
-			return -EIO;
 		goto again;
 	}
 
@@ -672,6 +702,7 @@ again:
 	}
 out:
 	mutex_unlock(&nsock->tx_lock);
+	nbd_config_put(nbd);
 	return ret;
 }
 
@@ -711,6 +742,7 @@ static int nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
 static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
 			  unsigned long arg)
 {
+	struct nbd_config *config = nbd->config;
 	struct socket *sock;
 	struct nbd_sock **socks;
 	struct nbd_sock *nsock;
@@ -729,7 +761,7 @@ static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
 		return -EINVAL;
 	}
 
-	socks = krealloc(nbd->socks, (nbd->num_connections + 1) *
+	socks = krealloc(config->socks, (config->num_connections + 1) *
 			 sizeof(struct nbd_sock *), GFP_KERNEL);
 	if (!socks) {
 		sockfd_put(sock);
@@ -741,7 +773,7 @@ static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
 		return -ENOMEM;
 	}
 
-	nbd->socks = socks;
+	config->socks = socks;
 
 	nsock->fallback_index = -1;
 	nsock->dead = false;
@@ -749,7 +781,7 @@ static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
 	nsock->sock = sock;
 	nsock->pending = NULL;
 	nsock->sent = 0;
-	socks[nbd->num_connections++] = nsock;
+	socks[config->num_connections++] = nsock;
 
 	if (max_part)
 		bdev->bd_invalidated = 1;
@@ -759,11 +791,7 @@ static int nbd_add_socket(struct nbd_device *nbd, struct block_device *bdev,
 /* Reset all properties of an NBD device */
 static void nbd_reset(struct nbd_device *nbd)
 {
-	nbd->runtime_flags = 0;
-	nbd->blksize = 1024;
-	nbd->bytesize = 0;
-	set_capacity(nbd->disk, 0);
-	nbd->flags = 0;
+	nbd->config = NULL;
 	nbd->tag_set.timeout = 0;
 	queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
 }
@@ -782,11 +810,12 @@ static void nbd_bdev_reset(struct block_device *bdev)
 
 static void nbd_parse_flags(struct nbd_device *nbd, struct block_device *bdev)
 {
-	if (nbd->flags & NBD_FLAG_READ_ONLY)
+	struct nbd_config *config = nbd->config;
+	if (config->flags & NBD_FLAG_READ_ONLY)
 		set_device_ro(bdev, true);
-	if (nbd->flags & NBD_FLAG_SEND_TRIM)
+	if (config->flags & NBD_FLAG_SEND_TRIM)
 		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
-	if (nbd->flags & NBD_FLAG_SEND_FLUSH)
+	if (config->flags & NBD_FLAG_SEND_FLUSH)
 		blk_queue_write_cache(nbd->disk->queue, true, false);
 	else
 		blk_queue_write_cache(nbd->disk->queue, false, false);
@@ -794,6 +823,7 @@ static void nbd_parse_flags(struct nbd_device *nbd, struct block_device *bdev)
 
 static void send_disconnects(struct nbd_device *nbd)
 {
+	struct nbd_config *config = nbd->config;
 	struct nbd_request request = {
 		.magic = htonl(NBD_REQUEST_MAGIC),
 		.type = htonl(NBD_CMD_DISC),
@@ -802,7 +832,7 @@ static void send_disconnects(struct nbd_device *nbd)
 	struct iov_iter from;
 	int i, ret;
 
-	for (i = 0; i < nbd->num_connections; i++) {
+	for (i = 0; i < config->num_connections; i++) {
 		iov_iter_kvec(&from, WRITE | ITER_KVEC, &iov, 1, sizeof(request));
 		ret = sock_xmit(nbd, i, 1, &from, 0, NULL);
 		if (ret <= 0)
@@ -813,20 +843,15 @@ static void send_disconnects(struct nbd_device *nbd)
 
 static int nbd_disconnect(struct nbd_device *nbd, struct block_device *bdev)
 {
-	dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
-	if (!nbd->socks)
-		return -EINVAL;
+	struct nbd_config *config = nbd->config;
 
+	dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
 	mutex_unlock(&nbd->config_lock);
 	fsync_bdev(bdev);
 	mutex_lock(&nbd->config_lock);
 
-	/* Check again after getting mutex back.  */
-	if (!nbd->socks)
-		return -EINVAL;
-
 	if (!test_and_set_bit(NBD_DISCONNECT_REQUESTED,
-			      &nbd->runtime_flags))
+			      &config->runtime_flags))
 		send_disconnects(nbd);
 	return 0;
 }
@@ -838,51 +863,63 @@ static int nbd_clear_sock(struct nbd_device *nbd, struct block_device *bdev)
 
 	__invalidate_device(bdev, true);
 	nbd_bdev_reset(bdev);
-	/*
-	 * We want to give the run thread a chance to wait for everybody
-	 * to clean up and then do it's own cleanup.
-	 */
-	if (!test_bit(NBD_RUNNING, &nbd->runtime_flags) &&
-	    nbd->num_connections) {
-		int i;
+	nbd->task_setup = NULL;
+	return 0;
+}
+
+static void nbd_config_put(struct nbd_device *nbd)
+{
+	if (refcount_dec_and_mutex_lock(&nbd->config_refs,
+					&nbd->config_lock)) {
+		struct block_device *bdev;
+		struct nbd_config *config = nbd->config;
 
-		for (i = 0; i < nbd->num_connections; i++) {
-			sockfd_put(nbd->socks[i]->sock);
-			kfree(nbd->socks[i]);
+		bdev = bdget_disk(nbd->disk, 0);
+		if (!bdev) {
+			mutex_unlock(&nbd->config_lock);
+			return;
 		}
-		kfree(nbd->socks);
-		nbd->socks = NULL;
-		nbd->num_connections = 0;
-	}
-	nbd->task_setup = NULL;
 
-	return 0;
+		nbd_dev_dbg_close(nbd);
+		nbd_size_clear(nbd, bdev);
+		if (test_and_clear_bit(NBD_HAS_PID_FILE,
+				       &config->runtime_flags))
+			device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
+		nbd->task_recv = NULL;
+		nbd_clear_sock(nbd, bdev);
+		if (config->num_connections) {
+			int i;
+			for (i = 0; i < config->num_connections; i++) {
+				sockfd_put(config->socks[i]->sock);
+				kfree(config->socks[i]);
+			}
+			kfree(config->socks);
+		}
+		nbd_reset(nbd);
+		mutex_unlock(&nbd->config_lock);
+		bdput(bdev);
+		module_put(THIS_MODULE);
+	}
 }
 
 static int nbd_start_device(struct nbd_device *nbd, struct block_device *bdev)
 {
-	struct recv_thread_args *args;
-	int num_connections = nbd->num_connections;
+	struct nbd_config *config = nbd->config;
+	int num_connections = config->num_connections;
 	int error = 0, i;
 
 	if (nbd->task_recv)
 		return -EBUSY;
-	if (!nbd->socks)
+	if (!config->socks)
 		return -EINVAL;
+
 	if (num_connections > 1 &&
-	    !(nbd->flags & NBD_FLAG_CAN_MULTI_CONN)) {
+	    !(config->flags & NBD_FLAG_CAN_MULTI_CONN)) {
 		dev_err(disk_to_dev(nbd->disk), "server does not support multiple connections per device.\n");
-		error = -EINVAL;
-		goto out_err;
+		return -EINVAL;
 	}
 
-	set_bit(NBD_RUNNING, &nbd->runtime_flags);
-	blk_mq_update_nr_hw_queues(&nbd->tag_set, nbd->num_connections);
-	args = kcalloc(num_connections, sizeof(*args), GFP_KERNEL);
-	if (!args) {
-		error = -ENOMEM;
-		goto out_err;
-	}
+	blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections);
 	nbd->task_recv = current;
 	mutex_unlock(&nbd->config_lock);
 
@@ -891,41 +928,40 @@ static int nbd_start_device(struct nbd_device *nbd, struct block_device *bdev)
 	error = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
 	if (error) {
 		dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
-		goto out_recv;
+		return error;
 	}
+	set_bit(NBD_HAS_PID_FILE, &config->runtime_flags);
 
 	nbd_size_update(nbd, bdev);
 
 	nbd_dev_dbg_init(nbd);
 	for (i = 0; i < num_connections; i++) {
-		sk_set_memalloc(nbd->socks[i]->sock->sk);
-		atomic_inc(&nbd->recv_threads);
-		INIT_WORK(&args[i].work, recv_work);
-		args[i].nbd = nbd;
-		args[i].index = i;
-		queue_work(recv_workqueue, &args[i].work);
+		struct recv_thread_args *args;
+
+		args = kzalloc(sizeof(*args), GFP_KERNEL);
+		if (!args) {
+			sock_shutdown(nbd);
+			return -ENOMEM;
+		}
+		sk_set_memalloc(config->socks[i]->sock->sk);
+		atomic_inc(&config->recv_threads);
+		refcount_inc(&nbd->config_refs);
+		INIT_WORK(&args->work, recv_work);
+		args->nbd = nbd;
+		args->index = i;
+		queue_work(recv_workqueue, &args->work);
 	}
-	wait_event_interruptible(nbd->recv_wq,
-				 atomic_read(&nbd->recv_threads) == 0);
-	for (i = 0; i < num_connections; i++)
-		flush_work(&args[i].work);
-	nbd_dev_dbg_close(nbd);
-	nbd_size_clear(nbd, bdev);
-	device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
-out_recv:
+	error = wait_event_interruptible(config->recv_wq,
+					 atomic_read(&config->recv_threads) == 0);
+	if (error)
+		sock_shutdown(nbd);
 	mutex_lock(&nbd->config_lock);
-	nbd->task_recv = NULL;
-out_err:
-	clear_bit(NBD_RUNNING, &nbd->runtime_flags);
-	nbd_clear_sock(nbd, bdev);
 
 	/* user requested, ignore socket errors */
-	if (test_bit(NBD_DISCONNECT_REQUESTED, &nbd->runtime_flags))
+	if (test_bit(NBD_DISCONNECT_REQUESTED, &config->runtime_flags))
 		error = 0;
-	if (test_bit(NBD_TIMEDOUT, &nbd->runtime_flags))
+	if (test_bit(NBD_TIMEDOUT, &config->runtime_flags))
 		error = -ETIMEDOUT;
-
-	nbd_reset(nbd);
 	return error;
 }
 
@@ -933,6 +969,8 @@ out_err:
 static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		       unsigned int cmd, unsigned long arg)
 {
+	struct nbd_config *config = nbd->config;
+
 	switch (cmd) {
 	case NBD_DISCONNECT:
 		return nbd_disconnect(nbd, bdev);
@@ -942,14 +980,14 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		return nbd_add_socket(nbd, bdev, arg);
 	case NBD_SET_BLKSIZE:
 		nbd_size_set(nbd, bdev, arg,
-			     div_s64(nbd->bytesize, arg));
+			     div_s64(config->bytesize, arg));
 		return 0;
 	case NBD_SET_SIZE:
-		nbd_size_set(nbd, bdev, nbd->blksize,
-			     div_s64(arg, nbd->blksize));
+		nbd_size_set(nbd, bdev, config->blksize,
+			     div_s64(arg, config->blksize));
 		return 0;
 	case NBD_SET_SIZE_BLOCKS:
-		nbd_size_set(nbd, bdev, nbd->blksize, arg);
+		nbd_size_set(nbd, bdev, config->blksize, arg);
 		return 0;
 	case NBD_SET_TIMEOUT:
 		if (arg) {
@@ -959,7 +997,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		return 0;
 
 	case NBD_SET_FLAGS:
-		nbd->flags = arg;
+		config->flags = arg;
 		return 0;
 	case NBD_DO_IT:
 		return nbd_start_device(nbd, bdev);
@@ -988,18 +1026,70 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	BUG_ON(nbd->magic != NBD_MAGIC);
-
 	mutex_lock(&nbd->config_lock);
 	error = __nbd_ioctl(bdev, nbd, cmd, arg);
 	mutex_unlock(&nbd->config_lock);
-
 	return error;
 }
 
+static struct nbd_config *nbd_alloc_config(void)
+{
+	struct nbd_config *config;
+
+	config = kzalloc(sizeof(struct nbd_config), GFP_NOFS);
+	if (!config)
+		return NULL;
+	atomic_set(&config->recv_threads, 0);
+	init_waitqueue_head(&config->recv_wq);
+	config->blksize = 1024;
+	try_module_get(THIS_MODULE);
+	return config;
+}
+
+static int nbd_open(struct block_device *bdev, fmode_t mode)
+{
+	struct nbd_device *nbd;
+	int ret = 0;
+
+	mutex_lock(&nbd_index_mutex);
+	nbd = bdev->bd_disk->private_data;
+	if (!nbd) {
+		ret = -ENXIO;
+		goto out;
+	}
+	if (!refcount_inc_not_zero(&nbd->config_refs)) {
+		struct nbd_config *config;
+
+		mutex_lock(&nbd->config_lock);
+		if (refcount_inc_not_zero(&nbd->config_refs)) {
+			mutex_unlock(&nbd->config_lock);
+			goto out;
+		}
+		config = nbd->config = nbd_alloc_config();
+		if (!config) {
+			ret = -ENOMEM;
+			mutex_unlock(&nbd->config_lock);
+			goto out;
+		}
+		refcount_set(&nbd->config_refs, 1);
+		mutex_unlock(&nbd->config_lock);
+	}
+out:
+	mutex_unlock(&nbd_index_mutex);
+	return ret;
+}
+
+static void nbd_release(struct gendisk *disk, fmode_t mode)
+{
+	struct nbd_device *nbd = disk->private_data;
+	nbd_config_put(nbd);
+}
+
 static const struct block_device_operations nbd_fops =
 {
 	.owner =	THIS_MODULE,
+	.open =		nbd_open,
+	.release =	nbd_release,
 	.ioctl =	nbd_ioctl,
 	.compat_ioctl =	nbd_ioctl,
 };
@@ -1031,7 +1121,7 @@ static const struct file_operations nbd_dbg_tasks_ops = {
 static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
 {
 	struct nbd_device *nbd = s->private;
-	u32 flags = nbd->flags;
+	u32 flags = nbd->config->flags;
 
 	seq_printf(s, "Hex: 0x%08x\n\n", flags);
 
@@ -1064,6 +1154,7 @@ static const struct file_operations nbd_dbg_flags_ops = {
 static int nbd_dev_dbg_init(struct nbd_device *nbd)
 {
 	struct dentry *dir;
+	struct nbd_config *config = nbd->config;
 
 	if (!nbd_dbg_dir)
 		return -EIO;
@@ -1074,12 +1165,12 @@ static int nbd_dev_dbg_init(struct nbd_device *nbd)
 			nbd_name(nbd));
 		return -EIO;
 	}
-	nbd->dbg_dir = dir;
+	config->dbg_dir = dir;
 
 	debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_ops);
-	debugfs_create_u64("size_bytes", 0444, dir, &nbd->bytesize);
+	debugfs_create_u64("size_bytes", 0444, dir, &config->bytesize);
 	debugfs_create_u32("timeout", 0444, dir, &nbd->tag_set.timeout);
-	debugfs_create_u64("blocksize", 0444, dir, &nbd->blksize);
+	debugfs_create_u64("blocksize", 0444, dir, &config->blksize);
 	debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_ops);
 
 	return 0;
@@ -1087,7 +1178,7 @@ static int nbd_dev_dbg_init(struct nbd_device *nbd)
 
 static void nbd_dev_dbg_close(struct nbd_device *nbd)
 {
-	debugfs_remove_recursive(nbd->dbg_dir);
+	debugfs_remove_recursive(nbd->config->dbg_dir);
 }
 
 static int nbd_dbg_init(void)
@@ -1148,7 +1239,6 @@ static const struct blk_mq_ops nbd_mq_ops = {
 static void nbd_dev_remove(struct nbd_device *nbd)
 {
 	struct gendisk *disk = nbd->disk;
-	nbd->magic = 0;
 	if (disk) {
 		del_gendisk(disk);
 		blk_cleanup_queue(disk->queue);
@@ -1217,14 +1307,13 @@ static int nbd_dev_add(int index)
 	blk_queue_max_hw_sectors(disk->queue, 65536);
 	disk->queue->limits.max_sectors = 256;
 
-	nbd->magic = NBD_MAGIC;
 	mutex_init(&nbd->config_lock);
+	refcount_set(&nbd->config_refs, 0);
 	disk->major = NBD_MAJOR;
 	disk->first_minor = index << part_shift;
 	disk->fops = &nbd_fops;
 	disk->private_data = nbd;
 	sprintf(disk->disk_name, "nbd%d", index);
-	init_waitqueue_head(&nbd->recv_wq);
 	nbd_reset(nbd);
 	add_disk(disk);
 	return index;