1 files changed, 33 insertions, 0 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 96eb9fef7bd2..0eb9a4da069e 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -54,6 +54,7 @@
 #include "version.h"
 #include "export.h"
 #include "compression.h"
+#include "rcu-string.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/btrfs.h>
@@ -1482,12 +1483,44 @@ static void btrfs_fs_dirty_inode(struct inode *inode, int flags)
                                    "error %d\n", btrfs_ino(inode), ret);
 }
 
+static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
+{
+        struct btrfs_fs_info *fs_info = btrfs_sb(root->d_sb);
+        struct btrfs_fs_devices *cur_devices;
+        struct btrfs_device *dev, *first_dev = NULL;
+        struct list_head *head;
+        struct rcu_string *name;
+
+        mutex_lock(&fs_info->fs_devices->device_list_mutex);
+        cur_devices = fs_info->fs_devices;
+        while (cur_devices) {
+                head = &cur_devices->devices;
+                list_for_each_entry(dev, head, dev_list) {
+                        if (!first_dev || dev->devid < first_dev->devid)
+                                first_dev = dev;
+                }
+                cur_devices = cur_devices->seed;
+        }
+
+        if (first_dev) {
+                rcu_read_lock();
+                name = rcu_dereference(first_dev->name);
+                seq_escape(m, name->str, " \t\n\\");
+                rcu_read_unlock();
+        } else {
+                WARN_ON(1);
+        }
+        mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+        return 0;
+}
+
 static const struct super_operations btrfs_super_ops = {
         .drop_inode     = btrfs_drop_inode,
         .evict_inode    = btrfs_evict_inode,
         .put_super      = btrfs_put_super,
         .sync_fs        = btrfs_sync_fs,
         .show_options   = btrfs_show_options,
+        .show_devname   = btrfs_show_devname,
         .write_inode    = btrfs_write_inode,
         .dirty_inode    = btrfs_fs_dirty_inode,
         .alloc_inode    = btrfs_alloc_inode,