Introduce RCU string API

index d897ef8..9f4ac42 100644
@@ -95,6 +95,7 @@
 #include <linux/genhd.h>
 #include <linux/blkdev.h>
 #include <linux/vmalloc.h>
+#include <linux/rcustring.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "hash.h"

@@ -104,7 +105,6 @@
 #include "print-tree.h"
 #include "locking.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 
 #define BTRFSIC_BLOCK_HASHTABLE_SIZE 0x10000
 #define BTRFSIC_BLOCK_LINK_HASHTABLE_SIZE 0x10000

@@ -848,8 +848,8 @@ static int btrfsic_process_superblock_dev_mirror(
 			printk_in_rcu(KERN_INFO "New initial S-block (bdev %p, %s)"
 				     " @%llu (%s/%llu/%d)\n",
 				     superblock_bdev,
-				     rcu_str_deref(device->name), dev_bytenr,
-				     dev_state->name, dev_bytenr,
+				     rcu_string_dereference(device->name),
+				     dev_bytenr, dev_state->name, dev_bytenr,
 				     superblock_mirror_num);
 		list_add(&superblock_tmp->all_blocks_node,
 			 &state->all_blocks_list);

index ca6a3a3..51133ea 100644
@@ -25,6 +25,7 @@
 #include <linux/capability.h>
 #include <linux/kthread.h>
 #include <linux/math64.h>
+#include <linux/rcustring.h>
 #include <asm/div64.h>
 #include "ctree.h"
 #include "extent_map.h"

@@ -34,7 +35,6 @@
 #include "volumes.h"
 #include "async-thread.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 #include "dev-replace.h"
 #include "sysfs.h"
 

@@ -379,9 +379,9 @@ int btrfs_dev_replace_start(struct btrfs_root *root,
 	printk_in_rcu(KERN_INFO
 		      "BTRFS: dev_replace from %s (devid %llu) to %s started\n",
 		      src_device->missing ? "<missing disk>" :
-		        rcu_str_deref(src_device->name),
+		      rcu_string_dereference(src_device->name),
 		      src_device->devid,
-		      rcu_str_deref(tgt_device->name));
+		      rcu_string_dereference(tgt_device->name));
 
 	/*
 	 * from now on, the writes to the srcdev are all duplicated to

@@ -532,9 +532,10 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 		printk_in_rcu(KERN_ERR
 			      "BTRFS: btrfs_scrub_dev(%s, %llu, %s) failed %d\n",
 			      src_device->missing ? "<missing disk>" :
-			        rcu_str_deref(src_device->name),
+			      rcu_string_dereference(src_device->name),
 			      src_device->devid,
-			      rcu_str_deref(tgt_device->name), scrub_ret);
+			      rcu_string_dereference(tgt_device->name),
+			      scrub_ret);
 		btrfs_dev_replace_unlock(dev_replace);
 		mutex_unlock(&root->fs_info->chunk_mutex);
 		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);

@@ -549,9 +550,9 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 	printk_in_rcu(KERN_INFO
 		      "BTRFS: dev_replace from %s (devid %llu) to %s finished\n",
 		      src_device->missing ? "<missing disk>" :
-		        rcu_str_deref(src_device->name),
+		      rcu_string_dereference(src_device->name),
 		      src_device->devid,
-		      rcu_str_deref(tgt_device->name));
+		      rcu_string_dereference(tgt_device->name));
 	tgt_device->is_tgtdev_for_dev_replace = 0;
 	tgt_device->devid = src_device->devid;
 	src_device->devid = BTRFS_DEV_REPLACE_DEVID;

@@ -819,10 +820,10 @@ static int btrfs_dev_replace_kthread(void *data)
 		printk_in_rcu(KERN_INFO
 			"BTRFS: continuing dev_replace from %s (devid %llu) to %s @%u%%\n",
 			dev_replace->srcdev->missing ? "<missing disk>" :
-			rcu_str_deref(dev_replace->srcdev->name),
+			rcu_string_dereference(dev_replace->srcdev->name),
 			dev_replace->srcdev->devid,
 			dev_replace->tgtdev ?
-			rcu_str_deref(dev_replace->tgtdev->name) :
+			rcu_string_dereference(dev_replace->tgtdev->name) :
 			"<missing target disk>",
 			(unsigned int)progress);
 	}

index 8c63419..a13b7fc 100644
@@ -31,6 +31,7 @@
 #include <linux/ratelimit.h>
 #include <linux/uuid.h>
 #include <linux/semaphore.h>
+#include <linux/rcustring.h>
 #include <asm/unaligned.h>
 #include "ctree.h"
 #include "disk-io.h"

@@ -44,7 +45,6 @@
 #include "free-space-cache.h"
 #include "inode-map.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 #include "dev-replace.h"
 #include "raid56.h"
 #include "sysfs.h"

@@ -3062,7 +3062,7 @@ static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 
 		printk_ratelimited_in_rcu(KERN_WARNING "BTRFS: lost page write due to "
 					  "I/O error on %s\n",
-					  rcu_str_deref(device->name));
+					  rcu_string_dereference(device->name));
 		/* note, we dont' set_buffer_write_io_error because we have
 		 * our own ways of dealing with the IO errors
 		 */

@@ -3251,7 +3251,7 @@ static int write_dev_flush(struct btrfs_device *device, int wait)
 
 		if (bio_flagged(bio, BIO_EOPNOTSUPP)) {
 			printk_in_rcu("BTRFS: disabling barriers on dev %s\n",
-				      rcu_str_deref(device->name));
+				      rcu_string_dereference(device->name));
 			device->nobarriers = 1;
 		} else if (!bio_flagged(bio, BIO_UPTODATE)) {
 			ret = -EIO;

index 4ebabd2..57cd6a5 100644
@@ -11,6 +11,7 @@
 #include <linux/pagevec.h>
 #include <linux/prefetch.h>
 #include <linux/cleancache.h>
+#include <linux/rcustring.h>
 #include "extent_io.h"
 #include "extent_map.h"
 #include "ctree.h"

@@ -18,7 +19,6 @@
 #include "volumes.h"
 #include "check-integrity.h"
 #include "locking.h"
-#include "rcu-string.h"
 #include "backref.h"
 
 static struct kmem_cache *extent_state_cache;

@@ -2075,7 +2075,7 @@ int repair_io_failure(struct inode *inode, u64 start, u64 length, u64 logical,
 	printk_ratelimited_in_rcu(KERN_INFO
 				  "BTRFS: read error corrected: ino %llu off %llu (dev %s sector %llu)\n",
 				  btrfs_ino(inode), start,
-				  rcu_str_deref(dev->name), sector);
+				  rcu_string_dereference(dev->name), sector);
 	bio_put(bio);
 	return 0;
 }

index d49fe8a..7ca1cad 100644
@@ -44,6 +44,7 @@
 #include <linux/uuid.h>
 #include <linux/btrfs.h>
 #include <linux/uaccess.h>
+#include <linux/rcustring.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"

@@ -53,7 +54,6 @@
 #include "locking.h"
 #include "inode-map.h"
 #include "backref.h"
-#include "rcu-string.h"
 #include "send.h"
 #include "dev-replace.h"
 #include "props.h"

@@ -1568,7 +1568,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 	new_size *= root->sectorsize;
 
 	printk_in_rcu(KERN_INFO "BTRFS: new size for %s is %llu\n",
-		      rcu_str_deref(device->name), new_size);
+		      rcu_string_dereference(device->name), new_size);
 
 	if (new_size > old_size) {
 		trans = btrfs_start_transaction(root, 0);

index 8ab2a17..44573bf 100644
@@ -32,6 +32,7 @@
 #include <linux/list_sort.h>
 #include <linux/raid/xor.h>
 #include <linux/vmalloc.h>
+#include <linux/rcustring.h>
 #include <asm/div64.h>
 #include "ctree.h"
 #include "extent_map.h"

@@ -42,7 +43,6 @@
 #include "raid56.h"
 #include "async-thread.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 
 /* set when additional merges to this rbio are not allowed */
 #define RBIO_RMW_LOCKED_BIT	1

56 lines not on this page · raw message

index f2bb13a..1807101 100644
@@ -18,6 +18,7 @@
 
 #include <linux/blkdev.h>
 #include <linux/ratelimit.h>
+#include <linux/rcustring.h>
 #include "ctree.h"
 #include "volumes.h"
 #include "disk-io.h"

@@ -27,7 +28,6 @@
 #include "extent_io.h"
 #include "dev-replace.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 #include "raid56.h"
 
 /*

@@ -562,7 +562,8 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 		printk_in_rcu(KERN_WARNING "BTRFS: %s at logical %llu on dev "
 			"%s, sector %llu, root %llu, inode %llu, offset %llu, "
 			"length %llu, links %u (path: %s)\n", swarn->errstr,
-			swarn->logical, rcu_str_deref(swarn->dev->name),
+			swarn->logical,
+			rcu_string_dereference(swarn->dev->name),
 			(unsigned long long)swarn->sector, root, inum, offset,
 			min(isize - offset, (u64)PAGE_SIZE), nlink,
 			(char *)(unsigned long)ipath->fspath->val[i]);

@@ -574,7 +575,7 @@ err:
 	printk_in_rcu(KERN_WARNING "BTRFS: %s at logical %llu on dev "
 		"%s, sector %llu, root %llu, inode %llu, offset %llu: path "
 		"resolving failed with ret=%d\n", swarn->errstr,
-		swarn->logical, rcu_str_deref(swarn->dev->name),
+		swarn->logical, rcu_string_dereference(swarn->dev->name),
 		(unsigned long long)swarn->sector, root, inum, offset, ret);
 
 	free_ipath(ipath);

@@ -632,7 +633,7 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 				"BTRFS: %s at logical %llu on dev %s, "
 				"sector %llu: metadata %s (level %d) in tree "
 				"%llu\n", errstr, swarn.logical,
-				rcu_str_deref(dev->name),
+				rcu_string_dereference(dev->name),
 				(unsigned long long)swarn.sector,
 				ref_level ? "node" : "leaf",
 				ret < 0 ? -1 : ref_level,

@@ -831,7 +832,7 @@ out:
 			num_uncorrectable_read_errors);
 		printk_ratelimited_in_rcu(KERN_ERR "BTRFS: "
 		    "unable to fixup (nodatasum) error at logical %llu on dev %s\n",
-			fixup->logical, rcu_str_deref(fixup->dev->name));
+		    fixup->logical, rcu_string_dereference(fixup->dev->name));
 	}
 
 	btrfs_free_path(path);

@@ -1249,7 +1250,7 @@ corrected_error:
 			spin_unlock(&sctx->stat_lock);
 			printk_ratelimited_in_rcu(KERN_ERR
 				"BTRFS: fixed up error at logical %llu on dev %s\n",
-				logical, rcu_str_deref(dev->name));
+				logical, rcu_string_dereference(dev->name));
 		}
 	} else {
 did_not_correct_error:

@@ -1258,7 +1259,7 @@ did_not_correct_error:
 		spin_unlock(&sctx->stat_lock);
 		printk_ratelimited_in_rcu(KERN_ERR
 			"BTRFS: unable to fixup (regular) error at logical %llu on dev %s\n",
-			logical, rcu_str_deref(dev->name));
+			logical, rcu_string_dereference(dev->name));
 	}
 
 out:

index 60f7cbe..0481020 100644
@@ -42,6 +42,7 @@
 #include <linux/cleancache.h>
 #include <linux/ratelimit.h>
 #include <linux/btrfs.h>
+#include <linux/rcustring.h>
 #include "delayed-inode.h"
 #include "ctree.h"
 #include "disk-io.h"

@@ -54,7 +55,6 @@
 #include "volumes.h"
 #include "export.h"
 #include "compression.h"
-#include "rcu-string.h"
 #include "dev-replace.h"
 #include "free-space-cache.h"
 #include "backref.h"

index 50c5a87..2231275 100644
@@ -27,6 +27,7 @@
 #include <linux/kthread.h>
 #include <linux/raid/pq.h>
 #include <linux/semaphore.h>
+#include <linux/rcustring.h>
 #include <asm/div64.h>
 #include "ctree.h"
 #include "extent_map.h"

@@ -37,7 +38,6 @@
 #include "raid56.h"
 #include "async-thread.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 #include "math.h"
 #include "dev-replace.h"
 #include "sysfs.h"

@@ -6474,7 +6474,7 @@ static int update_dev_stat_item(struct btrfs_trans_handle *trans,
 	if (ret < 0) {
 		printk_in_rcu(KERN_WARNING "BTRFS: "
 			"error %d while searching for dev_stats item for device %s!\n",
-			      ret, rcu_str_deref(device->name));
+			      ret, rcu_string_dereference(device->name));
 		goto out;
 	}
 

@@ -6485,7 +6485,7 @@ static int update_dev_stat_item(struct btrfs_trans_handle *trans,
 		if (ret != 0) {
 			printk_in_rcu(KERN_WARNING "BTRFS: "
 				"delete too small dev_stats item for device %s failed %d!\n",
-				      rcu_str_deref(device->name), ret);
+				rcu_string_dereference(device->name), ret);
 			goto out;
 		}
 		ret = 1;

@@ -6498,8 +6498,8 @@ static int update_dev_stat_item(struct btrfs_trans_handle *trans,
 					      &key, sizeof(*ptr));
 		if (ret < 0) {
 			printk_in_rcu(KERN_WARNING "BTRFS: "
-					  "insert dev_stats item for device %s failed %d!\n",
-				      rcu_str_deref(device->name), ret);
+				      "insert dev_stats item for device %s failed %d!\n",
+				      rcu_string_dereference(device->name), ret);
 			goto out;
 		}
 	}

@@ -6555,7 +6555,7 @@ static void btrfs_dev_stat_print_on_error(struct btrfs_device *dev)
 		return;
 	printk_ratelimited_in_rcu(KERN_ERR "BTRFS: "
 			   "bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u\n",
-			   rcu_str_deref(dev->name),
+			   rcu_string_dereference(dev->name),
 			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
 			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
 			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),

@@ -6575,7 +6575,7 @@ static void btrfs_dev_stat_print_on_load(struct btrfs_device *dev)
 
 	printk_in_rcu(KERN_INFO "BTRFS: "
 		   "bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u\n",
-	       rcu_str_deref(dev->name),
+	       rcu_string_dereference(dev->name),
 	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
 	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
 	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),

97 lines not on this page · raw message

index 2231275..ddd7483 100644
@@ -53,6 +53,45 @@ static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);
 DEFINE_MUTEX(uuid_mutex);
 static LIST_HEAD(fs_uuids);
 
+/*
+ * Dereference the device name under the uuid_mutex.
+ */
+static inline struct rcu_string *
+btrfs_dev_rcu_protected_name(struct btrfs_device *dev)
+__must_hold(&uuid_mutex)
+{
+	return rcu_dereference_protected(dev->name,
+					 lockdep_is_held(&uuid_mutex));
+}
+
+/*
+ * Use when the caller is the only possible updater.
+ */
+static inline struct rcu_string *
+btrfs_dev_rcu_only_name(struct btrfs_device *dev)
+{
+	return rcu_dereference_protected(dev->name, 1);
+}
+
+/*
+ * Rename a device under the uuid_mutex.
+ */
+static inline int btrfs_dev_rename(struct btrfs_device *dev, const char *name)
+__must_hold(&uuid_mutex)
+{
+	struct rcu_string *old_name, *new_name;
+
+	new_name = rcu_string_strdup(name, GFP_NOFS);
+	if (!new_name)
+		return -ENOMEM;
+
+	old_name = btrfs_dev_rcu_protected_name(dev);
+	rcu_assign_pointer(dev->name, new_name);
+	rcu_string_free(old_name);
+
+	return 0;
+}
+
 static struct btrfs_fs_devices *__alloc_fs_devices(void)
 {
 	struct btrfs_fs_devices *fs_devs;

@@ -104,7 +143,7 @@ static void free_fs_devices(struct btrfs_fs_devices *fs_devices)
 		device = list_entry(fs_devices->devices.next,
 				    struct btrfs_device, dev_list);
 		list_del(&device->dev_list);
-		rcu_string_free(device->name);
+		rcu_string_free(btrfs_dev_rcu_only_name(device));
 		kfree(device);
 	}
 	kfree(fs_devices);

@@ -485,12 +524,10 @@ static noinline int device_list_add(const char *path,
 			return PTR_ERR(device);
 		}
 
-		name = rcu_string_strdup(path, GFP_NOFS);
-		if (!name) {
+		if (btrfs_dev_rename(device, path)) {
 			kfree(device);
 			return -ENOMEM;
 		}
-		rcu_assign_pointer(device->name, name);
 
 		mutex_lock(&fs_devices->device_list_mutex);
 		list_add_rcu(&device->dev_list, &fs_devices->devices);

@@ -499,7 +536,11 @@ static noinline int device_list_add(const char *path,
 
 		ret = 1;
 		device->fs_devices = fs_devices;
-	} else if (!device->name || strcmp(device->name->str, path)) {
+	} else {
+		name = btrfs_dev_rcu_protected_name(device);
+		if (name && strcmp(name->str, path) == 0)
+			goto out;
+
 		/*
 		 * When FS is already mounted.
 		 * 1. If you are here and if the device->name is NULL that

@@ -537,17 +578,15 @@ static noinline int device_list_add(const char *path,
 			return -EEXIST;
 		}
 
-		name = rcu_string_strdup(path, GFP_NOFS);
-		if (!name)
+		if (btrfs_dev_rename(device, path))
 			return -ENOMEM;
-		rcu_string_free(device->name);
-		rcu_assign_pointer(device->name, name);
 		if (device->missing) {
 			fs_devices->missing_devices--;
 			device->missing = 0;
 		}
 	}
 
+out:
 	/*
 	 * Unmount does not free the btrfs_device struct but would zero
 	 * generation along with most of the other members. So just update

@@ -584,17 +623,12 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
 		if (IS_ERR(device))
 			goto error;
 
-		/*
-		 * This is ok to do without rcu read locked because we hold the
-		 * uuid mutex so nothing we touch in here is going to disappear.
-		 */
-		if (orig_dev->name) {
-			name = rcu_string_strdup(orig_dev->name->str, GFP_NOFS);
-			if (!name) {
+		name = btrfs_dev_rcu_protected_name(orig_dev);
+		if (name) {
+			if (btrfs_dev_rename(device, name->str)) {
 				kfree(device);
 				goto error;
 			}
-			rcu_assign_pointer(device->name, name);
 		}
 
 		list_add(&device->dev_list, &fs_devices->devices);

@@ -656,7 +690,7 @@ again:
 		}
 		list_del_init(&device->dev_list);
 		fs_devices->num_devices--;
-		rcu_string_free(device->name);
+		rcu_string_free(btrfs_dev_rcu_only_name(device));
 		kfree(device);
 	}
 

@@ -679,7 +713,7 @@ static void __free_device(struct work_struct *work)
 	if (device->bdev)
 		blkdev_put(device->bdev, device->mode);
 
-	rcu_string_free(device->name);
+	rcu_string_free(btrfs_dev_rcu_only_name(device));
 	kfree(device);
 }
 

@@ -721,11 +755,10 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 						device->uuid);
 		BUG_ON(IS_ERR(new_device)); /* -ENOMEM */
 
-		/* Safe because we are under uuid_mutex */
-		if (device->name) {
-			name = rcu_string_strdup(device->name->str, GFP_NOFS);
-			BUG_ON(!name); /* -ENOMEM */
-			rcu_assign_pointer(new_device->name, name);
+		name = btrfs_dev_rcu_protected_name(device);
+		if (name) {
+			if (btrfs_dev_rename(new_device, name->str))
+				BUG_ON(1); /* -ENOMEM */
 		}
 
 		list_replace_rcu(&device->dev_list, &new_device->dev_list);

@@ -784,18 +817,20 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 	u64 devid;
 	int seeding = 1;
 	int ret = 0;
+	struct rcu_string *name;
 
 	flags |= FMODE_EXCL;
 
 	list_for_each_entry(device, head, dev_list) {
 		if (device->bdev)
 			continue;
-		if (!device->name)
+		name = btrfs_dev_rcu_protected_name(device);
+		if (!name)
 			continue;
 
 		/* Just open everything we can; ignore failures here */
-		if (btrfs_get_bdev_and_sb(device->name->str, flags, holder, 1,
-					    &bdev, &bh))
+		if (btrfs_get_bdev_and_sb(name->str, flags, holder, 1, &bdev,
+					  &bh))
 			continue;
 
 		disk_super = (struct btrfs_super_block *)bh->b_data;

@@ -2142,7 +2177,7 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 
 	trans = btrfs_start_transaction(root, 0);
 	if (IS_ERR(trans)) {
-		rcu_string_free(device->name);
+		rcu_string_free(btrfs_dev_rcu_only_name(device));
 		kfree(device);
 		ret = PTR_ERR(trans);
 		goto error;

@@ -2279,7 +2314,7 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 
 error_trans:
 	btrfs_end_transaction(trans, root);
-	rcu_string_free(device->name);
+	rcu_string_free(btrfs_dev_rcu_only_name(device));
 	btrfs_kobj_rm_device(root->fs_info, device);
 	kfree(device);
 error:

index d6fe73c..234fd20 100644
@@ -54,7 +54,7 @@ struct btrfs_device {
 
 	struct btrfs_root *dev_root;
 
-	struct rcu_string *name;
+	struct rcu_string __rcu *name;
 
 	u64 generation;
 

index 7ca1cad..ee2528e 100644
@@ -2706,6 +2706,7 @@ static long btrfs_ioctl_dev_info(struct btrfs_root *root, void __user *arg)
 	struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
 	int ret = 0;
 	char *s_uuid = NULL;
+	struct rcu_string *name;
 
 	di_args = memdup_user(arg, sizeof(*di_args));
 	if (IS_ERR(di_args))

@@ -2726,17 +2727,16 @@ static long btrfs_ioctl_dev_info(struct btrfs_root *root, void __user *arg)
 	di_args->bytes_used = btrfs_device_get_bytes_used(dev);
 	di_args->total_bytes = btrfs_device_get_total_bytes(dev);
 	memcpy(di_args->uuid, dev->uuid, sizeof(di_args->uuid));
-	if (dev->name) {
-		struct rcu_string *name;
 
-		rcu_read_lock();
-		name = rcu_dereference(dev->name);
+	rcu_read_lock();
+	name = rcu_dereference(dev->name);
+	if (name) {
 		strncpy(di_args->path, name->str, sizeof(di_args->path));
-		rcu_read_unlock();
 		di_args->path[sizeof(di_args->path) - 1] = 0;
 	} else {
 		di_args->path[0] = '\0';
 	}
+	rcu_read_unlock();
 
 out:
 	mutex_unlock(&fs_devices->device_list_mutex);