btrfs: update latest_dev when we create a sprout device

When we add a device to the seed filesystem (sprouting) it is a new
filesystem (and fsid) on the device added. Update the latest_dev so
that /proc/self/mounts shows the correct device.

Example:

  $ btrfstune -S1 /dev/vg/seed
  $ mount /dev/vg/seed /btrfs
  mount: /btrfs: WARNING: device write-protected, mounted read-only.

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-seed /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

  $ btrfs dev add -f /dev/vg/new /btrfs

Before:

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-seed /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

After:

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-new /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3f0aff6..05eedab 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2627,6 +2627,8 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
                        btrfs_abort_transaction(trans, ret);
                        goto error_trans;
                }
+               btrfs_assign_next_active_device(fs_info->fs_devices->latest_dev,
+                                               device);
        }
 
        device->fs_devices = fs_devices;