Merge tag 'for-5.15/drivers-2021-08-30' of git://git.kernel.dk/linux-block

Pull block driver updates from Jens Axboe:
 "Sitting on top of the core block changes, here are the driver changes
  for the 5.15 merge window:

   - NVMe updates via Christoph:
       - suspend improvements for devices with an HMB (Keith Busch)
       - handle double completions more gacefull (Sagi Grimberg)
       - cleanup the selects for the nvme core code a bit (Sagi Grimberg)
       - don't update queue count when failing to set io queues (Ruozhu Li)
       - various nvmet connect fixes (Amit Engel)
       - cleanup lightnvm leftovers (Keith Busch, me)
       - small cleanups (Colin Ian King, Hou Pu)
       - add tracing for the Set Features command (Hou Pu)
       - CMB sysfs cleanups (Keith Busch)
       - add a mutex_destroy call (Keith Busch)

   - remove lightnvm subsystem. It's served its purpose and ultimately
     led to zoned nvme support, we no longer need it (Christoph)

   - revert floppy O_NDELAY fix (Denis)

   - nbd fixes (Hou, Pavel, Baokun)

   - nbd locking fixes (Tetsuo)

   - nbd device removal fixes (Christoph)

   - raid10 rcu warning fix (Xiao)

   - raid1 write behind fix (Guoqing)

   - rnbd fixes (Gioh, Md Haris)

   - misc fixes (Colin)"

* tag 'for-5.15/drivers-2021-08-30' of git://git.kernel.dk/linux-block: (42 commits)
  Revert "floppy: reintroduce O_NDELAY fix"
  raid1: ensure write behind bio has less than BIO_MAX_VECS sectors
  md/raid10: Remove unnecessary rcu_dereference in raid10_handle_discard
  nbd: remove nbd->destroy_complete
  nbd: only return usable devices from nbd_find_unused
  nbd: set nbd->index before releasing nbd_index_mutex
  nbd: prevent IDR lookups from finding partially initialized devices
  nbd: reset NBD to NULL when restarting in nbd_genl_connect
  nbd: add missing locking to the nbd_dev_add error path
  nvme: remove the unused NVME_NS_* enum
  nvme: remove nvm_ndev from ns
  nvme: Have NVME_FABRICS select NVME_CORE instead of transport drivers
  block: nbd: add sanity check for first_minor
  nvmet: check that host sqsize does not exceed ctrl MQES
  nvmet: avoid duplicate qid in connect cmd
  nvmet: pass back cntlid on successful completion
  nvme-rdma: don't update queue count when failing to set io queues
  nvme-tcp: don't update queue count when failing to set io queues
  nvme-tcp: pair send_mutex init with destroy
  nvme: allow user toggling hmb usage
  ...

6 files changed, 137 insertions, 121 deletions

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 87460e0e5c72..fef79ea52e3e 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4029,23 +4029,23 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
 	if (fdc_state[FDC(drive)].rawcmd == 1)
 		fdc_state[FDC(drive)].rawcmd = 2;
 
-	if (mode & (FMODE_READ|FMODE_WRITE)) {
-		drive_state[drive].last_checked = 0;
-		clear_bit(FD_OPEN_SHOULD_FAIL_BIT, &drive_state[drive].flags);
-		if (bdev_check_media_change(bdev))
-			floppy_revalidate(bdev->bd_disk);
-		if (test_bit(FD_DISK_CHANGED_BIT, &drive_state[drive].flags))
-			goto out;
-		if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &drive_state[drive].flags))
+	if (!(mode & FMODE_NDELAY)) {
+		if (mode & (FMODE_READ|FMODE_WRITE)) {
+			drive_state[drive].last_checked = 0;
+			clear_bit(FD_OPEN_SHOULD_FAIL_BIT,
+				  &drive_state[drive].flags);
+			if (bdev_check_media_change(bdev))
+				floppy_revalidate(bdev->bd_disk);
+			if (test_bit(FD_DISK_CHANGED_BIT, &drive_state[drive].flags))
+				goto out;
+			if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &drive_state[drive].flags))
+				goto out;
+		}
+		res = -EROFS;
+		if ((mode & FMODE_WRITE) &&
+		    !test_bit(FD_DISK_WRITABLE_BIT, &drive_state[drive].flags))
 			goto out;
 	}
-
-	res = -EROFS;
-
-	if ((mode & FMODE_WRITE) &&
-			!test_bit(FD_DISK_WRITABLE_BIT, &drive_state[drive].flags))
-		goto out;
-
 	mutex_unlock(&open_lock);
 	mutex_unlock(&floppy_mutex);
 	return 0;
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 19f5d5a8b16a..5170a630778d 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -49,6 +49,7 @@
 
 static DEFINE_IDR(nbd_index_idr);
 static DEFINE_MUTEX(nbd_index_mutex);
+static struct workqueue_struct *nbd_del_wq;
 static int nbd_total_devices = 0;
 
 struct nbd_sock {
@@ -113,12 +114,12 @@ struct nbd_device {
 	struct mutex config_lock;
 	struct gendisk *disk;
 	struct workqueue_struct *recv_workq;
+	struct work_struct remove_work;
 
 	struct list_head list;
 	struct task_struct *task_recv;
 	struct task_struct *task_setup;
 
-	struct completion *destroy_complete;
 	unsigned long flags;
 
 	char *backend;
@@ -237,32 +238,36 @@ static void nbd_dev_remove(struct nbd_device *nbd)
 {
 	struct gendisk *disk = nbd->disk;
 
-	if (disk) {
-		del_gendisk(disk);
-		blk_cleanup_disk(disk);
-		blk_mq_free_tag_set(&nbd->tag_set);
-	}
+	del_gendisk(disk);
+	blk_cleanup_disk(disk);
+	blk_mq_free_tag_set(&nbd->tag_set);
 
 	/*
-	 * Place this in the last just before the nbd is freed to
-	 * make sure that the disk and the related kobject are also
-	 * totally removed to avoid duplicate creation of the same
-	 * one.
+	 * Remove from idr after del_gendisk() completes, so if the same ID is
+	 * reused, the following add_disk() will succeed.
 	 */
-	if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) && nbd->destroy_complete)
-		complete(nbd->destroy_complete);
+	mutex_lock(&nbd_index_mutex);
+	idr_remove(&nbd_index_idr, nbd->index);
+	mutex_unlock(&nbd_index_mutex);
 
 	kfree(nbd);
 }
 
+static void nbd_dev_remove_work(struct work_struct *work)
+{
+	nbd_dev_remove(container_of(work, struct nbd_device, remove_work));
+}
+
 static void nbd_put(struct nbd_device *nbd)
 {
-	if (refcount_dec_and_mutex_lock(&nbd->refs,
-					&nbd_index_mutex)) {
-		idr_remove(&nbd_index_idr, nbd->index);
+	if (!refcount_dec_and_test(&nbd->refs))
+		return;
+
+	/* Call del_gendisk() asynchrounously to prevent deadlock */
+	if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags))
+		queue_work(nbd_del_wq, &nbd->remove_work);
+	else
 		nbd_dev_remove(nbd);
-		mutex_unlock(&nbd_index_mutex);
-	}
 }
 
 static int nbd_disconnected(struct nbd_config *config)
@@ -1388,6 +1393,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		       unsigned int cmd, unsigned long arg)
 {
 	struct nbd_config *config = nbd->config;
+	loff_t bytesize;
 
 	switch (cmd) {
 	case NBD_DISCONNECT:
@@ -1402,8 +1408,9 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 	case NBD_SET_SIZE:
 		return nbd_set_size(nbd, arg, config->blksize);
 	case NBD_SET_SIZE_BLOCKS:
-		return nbd_set_size(nbd, arg * config->blksize,
-				    config->blksize);
+		if (check_mul_overflow((loff_t)arg, config->blksize, &bytesize))
+			return -EINVAL;
+		return nbd_set_size(nbd, bytesize, config->blksize);
 	case NBD_SET_TIMEOUT:
 		nbd_set_cmd_timeout(nbd, arg);
 		return 0;
@@ -1665,7 +1672,7 @@ static const struct blk_mq_ops nbd_mq_ops = {
 	.timeout	= nbd_xmit_timeout,
 };
 
-static int nbd_dev_add(int index)
+static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
 {
 	struct nbd_device *nbd;
 	struct gendisk *disk;
@@ -1683,13 +1690,14 @@ static int nbd_dev_add(int index)
 	nbd->tag_set.flags = BLK_MQ_F_SHOULD_MERGE |
 		BLK_MQ_F_BLOCKING;
 	nbd->tag_set.driver_data = nbd;
-	nbd->destroy_complete = NULL;
+	INIT_WORK(&nbd->remove_work, nbd_dev_remove_work);
 	nbd->backend = NULL;
 
 	err = blk_mq_alloc_tag_set(&nbd->tag_set);
 	if (err)
 		goto out_free_nbd;
 
+	mutex_lock(&nbd_index_mutex);
 	if (index >= 0) {
 		err = idr_alloc(&nbd_index_idr, nbd, index, index + 1,
 				GFP_KERNEL);
@@ -1700,9 +1708,10 @@ static int nbd_dev_add(int index)
 		if (err >= 0)
 			index = err;
 	}
+	nbd->index = index;
+	mutex_unlock(&nbd_index_mutex);
 	if (err < 0)
 		goto out_free_tags;
-	nbd->index = index;
 
 	disk = blk_mq_alloc_disk(&nbd->tag_set, NULL);
 	if (IS_ERR(disk)) {
@@ -1726,38 +1735,65 @@ static int nbd_dev_add(int index)
 
 	mutex_init(&nbd->config_lock);
 	refcount_set(&nbd->config_refs, 0);
-	refcount_set(&nbd->refs, 1);
+	/*
+	 * Start out with a zero references to keep other threads from using
+	 * this device until it is fully initialized.
+	 */
+	refcount_set(&nbd->refs, 0);
 	INIT_LIST_HEAD(&nbd->list);
 	disk->major = NBD_MAJOR;
+
+	/* Too big first_minor can cause duplicate creation of
+	 * sysfs files/links, since first_minor will be truncated to
+	 * byte in __device_add_disk().
+	 */
 	disk->first_minor = index << part_shift;
+	if (disk->first_minor > 0xff) {
+		err = -EINVAL;
+		goto out_free_idr;
+	}
+
 	disk->minors = 1 << part_shift;
 	disk->fops = &nbd_fops;
 	disk->private_data = nbd;
 	sprintf(disk->disk_name, "nbd%d", index);
 	add_disk(disk);
+
+	/*
+	 * Now publish the device.
+	 */
+	refcount_set(&nbd->refs, refs);
 	nbd_total_devices++;
-	return index;
+	return nbd;
 
 out_free_idr:
+	mutex_lock(&nbd_index_mutex);
 	idr_remove(&nbd_index_idr, index);
+	mutex_unlock(&nbd_index_mutex);
 out_free_tags:
 	blk_mq_free_tag_set(&nbd->tag_set);
 out_free_nbd:
 	kfree(nbd);
 out:
-	return err;
+	return ERR_PTR(err);
 }
 
-static int find_free_cb(int id, void *ptr, void *data)
+static struct nbd_device *nbd_find_get_unused(void)
 {
-	struct nbd_device *nbd = ptr;
-	struct nbd_device **found = data;
+	struct nbd_device *nbd;
+	int id;
 
-	if (!refcount_read(&nbd->config_refs)) {
-		*found = nbd;
-		return 1;
+	lockdep_assert_held(&nbd_index_mutex);
+
+	idr_for_each_entry(&nbd_index_idr, nbd, id) {
+		if (refcount_read(&nbd->config_refs) ||
+		    test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags))
+			continue;
+		if (refcount_inc_not_zero(&nbd->refs))
+			return nbd;
 	}
-	return 0;
+
+	return NULL;
 }
 
 /* Netlink interface. */
@@ -1806,8 +1842,7 @@ static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd)
 
 static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 {
-	DECLARE_COMPLETION_ONSTACK(destroy_complete);
-	struct nbd_device *nbd = NULL;
+	struct nbd_device *nbd;
 	struct nbd_config *config;
 	int index = -1;
 	int ret;
@@ -1829,55 +1864,29 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 again:
 	mutex_lock(&nbd_index_mutex);
 	if (index == -1) {
-		ret = idr_for_each(&nbd_index_idr, &find_free_cb, &nbd);
-		if (ret == 0) {
-			int new_index;
-			new_index = nbd_dev_add(-1);
-			if (new_index < 0) {
-				mutex_unlock(&nbd_index_mutex);
-				printk(KERN_ERR "nbd: failed to add new device\n");
-				return new_index;
-			}
-			nbd = idr_find(&nbd_index_idr, new_index);
-		}
+		nbd = nbd_find_get_unused();
 	} else {
 		nbd = idr_find(&nbd_index_idr, index);
-		if (!nbd) {
-			ret = nbd_dev_add(index);
-			if (ret < 0) {
+		if (nbd) {
+			if ((test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&
+			     test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) ||
+			    !refcount_inc_not_zero(&nbd->refs)) {
 				mutex_unlock(&nbd_index_mutex);
-				printk(KERN_ERR "nbd: failed to add new device\n");
-				return ret;
+				pr_err("nbd: device at index %d is going down\n",
+					index);
+				return -EINVAL;
 			}
-			nbd = idr_find(&nbd_index_idr, index);
 		}
 	}
-	if (!nbd) {
-		printk(KERN_ERR "nbd: couldn't find device at index %d\n",
-		       index);
-		mutex_unlock(&nbd_index_mutex);
-		return -EINVAL;
-	}
-
-	if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&
-	    test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) {
-		nbd->destroy_complete = &destroy_complete;
-		mutex_unlock(&nbd_index_mutex);
-
-		/* Wait untill the the nbd stuff is totally destroyed */
-		wait_for_completion(&destroy_complete);
-		goto again;
-	}
+	mutex_unlock(&nbd_index_mutex);
 
-	if (!refcount_inc_not_zero(&nbd->refs)) {
-		mutex_unlock(&nbd_index_mutex);
-		if (index == -1)
-			goto again;
-		printk(KERN_ERR "nbd: device at index %d is going down\n",
-		       index);
-		return -EINVAL;
+	if (!nbd) {
+		nbd = nbd_dev_add(index, 2);
+		if (IS_ERR(nbd)) {
+			pr_err("nbd: failed to add new device\n");
+			return PTR_ERR(nbd);
+		}
 	}
-	mutex_unlock(&nbd_index_mutex);
 
 	mutex_lock(&nbd->config_lock);
 	if (refcount_read(&nbd->config_refs)) {
@@ -2424,16 +2433,21 @@ static int __init nbd_init(void)
 	if (register_blkdev(NBD_MAJOR, "nbd"))
 		return -EIO;
 
+	nbd_del_wq = alloc_workqueue("nbd-del", WQ_UNBOUND, 0);
+	if (!nbd_del_wq) {
+		unregister_blkdev(NBD_MAJOR, "nbd");
+		return -ENOMEM;
+	}
+
 	if (genl_register_family(&nbd_genl_family)) {
+		destroy_workqueue(nbd_del_wq);
 		unregister_blkdev(NBD_MAJOR, "nbd");
 		return -EINVAL;
 	}
 	nbd_dbg_init();
 
-	mutex_lock(&nbd_index_mutex);
 	for (i = 0; i < nbds_max; i++)
-		nbd_dev_add(i);
-	mutex_unlock(&nbd_index_mutex);
+		nbd_dev_add(i, 1);
 	return 0;
 }
 
@@ -2442,7 +2456,10 @@ static int nbd_exit_cb(int id, void *ptr, void *data)
 	struct list_head *list = (struct list_head *)data;
 	struct nbd_device *nbd = ptr;
 
-	list_add_tail(&nbd->list, list);
+	/* Skip nbd that is being removed asynchronously */
+	if (refcount_read(&nbd->refs))
+		list_add_tail(&nbd->list, list);
+
 	return 0;
 }
 
@@ -2465,6 +2482,9 @@ static void __exit nbd_cleanup(void)
 		nbd_put(nbd);
 	}
 
+	/* Also wait for nbd_dev_remove_work() completes */
+	destroy_workqueue(nbd_del_wq);
+
 	idr_destroy(&nbd_index_idr);
 	genl_unregister_family(&nbd_genl_family);
 	unregister_blkdev(NBD_MAJOR, "nbd");
diff --git a/drivers/block/rnbd/rnbd-clt-sysfs.c b/drivers/block/rnbd/rnbd-clt-sysfs.c
index 324afdd63a96..4b93fd83bf79 100644
--- a/drivers/block/rnbd/rnbd-clt-sysfs.c
+++ b/drivers/block/rnbd/rnbd-clt-sysfs.c
@@ -227,17 +227,17 @@ static ssize_t state_show(struct kobject *kobj,
 
 	switch (dev->dev_state) {
 	case DEV_STATE_INIT:
-		return snprintf(page, PAGE_SIZE, "init\n");
+		return sysfs_emit(page, "init\n");
 	case DEV_STATE_MAPPED:
 		/* TODO fix cli tool before changing to proper state */
-		return snprintf(page, PAGE_SIZE, "open\n");
+		return sysfs_emit(page, "open\n");
 	case DEV_STATE_MAPPED_DISCONNECTED:
 		/* TODO fix cli tool before changing to proper state */
-		return snprintf(page, PAGE_SIZE, "closed\n");
+		return sysfs_emit(page, "closed\n");
 	case DEV_STATE_UNMAPPED:
-		return snprintf(page, PAGE_SIZE, "unmapped\n");
+		return sysfs_emit(page, "unmapped\n");
 	default:
-		return snprintf(page, PAGE_SIZE, "unknown\n");
+		return sysfs_emit(page, "unknown\n");
 	}
 }
 
@@ -263,7 +263,7 @@ static ssize_t mapping_path_show(struct kobject *kobj,
 
 	dev = container_of(kobj, struct rnbd_clt_dev, kobj);
 
-	return scnprintf(page, PAGE_SIZE, "%s\n", dev->pathname);
+	return sysfs_emit(page, "%s\n", dev->pathname);
 }
 
 static struct kobj_attribute rnbd_clt_mapping_path_attr =
@@ -276,8 +276,7 @@ static ssize_t access_mode_show(struct kobject *kobj,
 
 	dev = container_of(kobj, struct rnbd_clt_dev, kobj);
 
-	return snprintf(page, PAGE_SIZE, "%s\n",
-			rnbd_access_mode_str(dev->access_mode));
+	return sysfs_emit(page, "%s\n", rnbd_access_mode_str(dev->access_mode));
 }
 
 static struct kobj_attribute rnbd_clt_access_mode =
@@ -286,8 +285,8 @@ static struct kobj_attribute rnbd_clt_access_mode =
 static ssize_t rnbd_clt_unmap_dev_show(struct kobject *kobj,
 					struct kobj_attribute *attr, char *page)
 {
-	return scnprintf(page, PAGE_SIZE, "Usage: echo <normal|force> > %s\n",
-			 attr->attr.name);
+	return sysfs_emit(page, "Usage: echo <normal|force> > %s\n",
+			  attr->attr.name);
 }
 
 static ssize_t rnbd_clt_unmap_dev_store(struct kobject *kobj,
@@ -357,9 +356,8 @@ static ssize_t rnbd_clt_resize_dev_show(struct kobject *kobj,
 					 struct kobj_attribute *attr,
 					 char *page)
 {
-	return scnprintf(page, PAGE_SIZE,
-			 "Usage: echo <new size in sectors> > %s\n",
-			 attr->attr.name);
+	return sysfs_emit(page, "Usage: echo <new size in sectors> > %s\n",
+			  attr->attr.name);
 }
 
 static ssize_t rnbd_clt_resize_dev_store(struct kobject *kobj,
@@ -390,8 +388,7 @@ static struct kobj_attribute rnbd_clt_resize_dev_attr =
 static ssize_t rnbd_clt_remap_dev_show(struct kobject *kobj,
 					struct kobj_attribute *attr, char *page)
 {
-	return scnprintf(page, PAGE_SIZE, "Usage: echo <1> > %s\n",
-			 attr->attr.name);
+	return sysfs_emit(page, "Usage: echo <1> > %s\n", attr->attr.name);
 }
 
 static ssize_t rnbd_clt_remap_dev_store(struct kobject *kobj,
@@ -436,7 +433,7 @@ static ssize_t session_show(struct kobject *kobj, struct kobj_attribute *attr,
 
 	dev = container_of(kobj, struct rnbd_clt_dev, kobj);
 
-	return scnprintf(page, PAGE_SIZE, "%s\n", dev->sess->sessname);
+	return sysfs_emit(page, "%s\n", dev->sess->sessname);
 }
 
 static struct kobj_attribute rnbd_clt_session_attr =
@@ -499,8 +496,8 @@ static ssize_t rnbd_clt_map_device_show(struct kobject *kobj,
 					 struct kobj_attribute *attr,
 					 char *page)
 {
-	return scnprintf(page, PAGE_SIZE,
-			 "Usage: echo \"[dest_port=server port number] sessname=<name of the rtrs session> path=<[srcaddr@]dstaddr> [path=<[srcaddr@]dstaddr>] device_path=<full path on remote side> [access_mode=<ro|rw|migration>] [nr_poll_queues=<number of queues>]\" > %s\n\naddr ::= [ ip:<ipv4> | ip:<ipv6> | gid:<gid> ]\n",
+	return sysfs_emit(page,
+			  "Usage: echo \"[dest_port=server port number] sessname=<name of the rtrs session> path=<[srcaddr@]dstaddr> [path=<[srcaddr@]dstaddr>] device_path=<full path on remote side> [access_mode=<ro|rw|migration>] [nr_poll_queues=<number of queues>]\" > %s\n\naddr ::= [ ip:<ipv4> | ip:<ipv6> | gid:<gid> ]\n",
 			 attr->attr.name);
 }
 
diff --git a/drivers/block/rnbd/rnbd-clt.c b/drivers/block/rnbd/rnbd-clt.c
index e9cc413495f0..bd4a41afbbfc 100644
--- a/drivers/block/rnbd/rnbd-clt.c
+++ b/drivers/block/rnbd/rnbd-clt.c
@@ -271,7 +271,7 @@ unlock:
 	 */
 	if (cpu_q)
 		*cpup = cpu_q->cpu;
-	put_cpu_var(sess->cpu_rr);
+	put_cpu_ptr(sess->cpu_rr);
 
 	if (q)
 		rnbd_clt_dev_requeue(q);
diff --git a/drivers/block/rnbd/rnbd-srv-sysfs.c b/drivers/block/rnbd/rnbd-srv-sysfs.c
index acf5fced11ef..4db98e0e76f0 100644
--- a/drivers/block/rnbd/rnbd-srv-sysfs.c
+++ b/drivers/block/rnbd/rnbd-srv-sysfs.c
@@ -90,8 +90,8 @@ static ssize_t read_only_show(struct kobject *kobj, struct kobj_attribute *attr,
 
 	sess_dev = container_of(kobj, struct rnbd_srv_sess_dev, kobj);
 
-	return scnprintf(page, PAGE_SIZE, "%d\n",
-			 !(sess_dev->open_flags & FMODE_WRITE));
+	return sysfs_emit(page, "%d\n",
+			  !(sess_dev->open_flags & FMODE_WRITE));
 }
 
 static struct kobj_attribute rnbd_srv_dev_session_ro_attr =
@@ -105,8 +105,8 @@ static ssize_t access_mode_show(struct kobject *kobj,
 
 	sess_dev = container_of(kobj, struct rnbd_srv_sess_dev, kobj);
 
-	return scnprintf(page, PAGE_SIZE, "%s\n",
-			 rnbd_access_mode_str(sess_dev->access_mode));
+	return sysfs_emit(page, "%s\n",
+			  rnbd_access_mode_str(sess_dev->access_mode));
 }
 
 static struct kobj_attribute rnbd_srv_dev_session_access_mode_attr =
@@ -119,7 +119,7 @@ static ssize_t mapping_path_show(struct kobject *kobj,
 
 	sess_dev = container_of(kobj, struct rnbd_srv_sess_dev, kobj);
 
-	return scnprintf(page, PAGE_SIZE, "%s\n", sess_dev->pathname);
+	return sysfs_emit(page, "%s\n", sess_dev->pathname);
 }
 
 static struct kobj_attribute rnbd_srv_dev_session_mapping_path_attr =
@@ -128,8 +128,8 @@ static struct kobj_attribute rnbd_srv_dev_session_mapping_path_attr =
 static ssize_t rnbd_srv_dev_session_force_close_show(struct kobject *kobj,
 					struct kobj_attribute *attr, char *page)
 {
-	return scnprintf(page, PAGE_SIZE, "Usage: echo 1 > %s\n",
-			 attr->attr.name);
+	return sysfs_emit(page, "Usage: echo 1 > %s\n",
+			  attr->attr.name);
 }
 
 static ssize_t rnbd_srv_dev_session_force_close_store(struct kobject *kobj,
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index d83fee21f6c5..715bfa8aca7f 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1092,7 +1092,6 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 	err = xlbd_reserve_minors(minor, nr_minors);
 	if (err)
 		return err;
-	err = -ENODEV;
 
 	memset(&info->tag_set, 0, sizeof(info->tag_set));
 	info->tag_set.ops = &blkfront_mq_ops;