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

For example:
 $ btrfstune -S1 /dev/vg/scratch1
 $ mount /dev/vg/scratch1 /btrfs
 mount: /btrfs: WARNING: device write-protected, mounted read-only.

 $ cat /proc/self/mounts | grep btrfs
 /dev/mapper/vg-scratch1 /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

 $ btrfs dev add -f /dev/vg/scratch0 /btrfs

Before:
 $ cat /proc/self/mounts | grep btrfs
 /dev/mapper/vg-scratch1 /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

After:
 $ cat /proc/self/mounts | grep btrfs
 /dev/mapper/vg-scratch0 /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

Signed-off-by: Anand Jain <redacted>
---
 fs/btrfs/volumes.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index ae317b0c39a3..8470c5b5f35e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c

@@ -2600,6 +2600,8 @@ 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;

-- 
2.31.1