Incorrect status/diff output

System information:

root@ubuntu:/# uname -a
Linux ubuntu 4.4.0-59-generic #80-Ubuntu SMP Fri Jan 6 17:47:47 UTC 2017 x86_64 x86_64 x86_64 
root@ubuntu:/# snapper --version
snapper 0.4.1
flags btrfs,lvm,ext4,xattrs,rollback,btrfs-quota,no-selinux

The problem is that sometimes when the user creates/deletes folders and moves files around, snapper can become confused what the changes between two snapshots are.

Here are the contents of the two problematic snapshots:

root@ubuntu:/# sh -c 'cd /mnt/shared/.snapshots/43/snapshot; find .'
.
./.snapshots
./a
./a/Lake McDonald.jpg
./a/d
./a/d/173.jpg
./b

root@ubuntu:/# sh -c 'cd /mnt/shared/.snapshots/47/snapshot; find .'
.
./.snapshots
./d
./d/173.jpg
./d/Lake McDonald.jpg
./d/Lake Tahoe Colors.jpg
./b

snapper output:

root@ubuntu:~# snapper list
Type   | #  | Pre # | Date                            | User | Cleanup  | Description | Userdata
-------+----+-------+---------------------------------+------+----------+-------------+---------
single | 0  |       |                                 | root |          | current     |
single | 22 |       | Tue 24 Jan 2017 12:00:08 PM EET | root | timeline | timeline    |
single | 43 |       | Tue 24 Jan 2017 12:14:28 PM EET | root |          |             |
single | 47 |       | Tue 24 Jan 2017 12:15:03 PM EET | root |          |             |
single | 48 |       | Tue 24 Jan 2017 12:15:18 PM EET | root |          |             |

root@ubuntu:/# snapper status 43..47
+..... /mnt/shared/b/b/d/Lake McDonald.jpg
-..... /mnt/shared/b/Lake McDonald.jpg
+..... /mnt/shared/d/Lake Tahoe Colors.jpg

root@ubuntu:/# snapper diff 43..47
/usr/bin/diff: /mnt/shared/.snapshots/43/snapshot/b/b/d/Lake McDonald.jpg: No such file or directory
/usr/bin/diff: /mnt/shared/.snapshots/47/snapshot/b/b/d/Lake McDonald.jpg: No such file or directory
/usr/bin/diff: /mnt/shared/.snapshots/43/snapshot/b/Lake McDonald.jpg: No such file or directory
/usr/bin/diff: /mnt/shared/.snapshots/47/snapshot/b/Lake McDonald.jpg: No such file or directory
Binary files /mnt/shared/.snapshots/43/snapshot/d/Lake Tahoe Colors.jpg and /mnt/shared/.snapshots/47/snapshot/d/Lake Tahoe Colors.jpg differ

What is incorrect here:

• status line 1: no such path exists
• status line 2: no such path exists
• diff line 5: path in snapshot 43 does not exist

I tested sending the same incremental snapshot using btrfs send/receive and the result looked ok to me, and it makes me believe this is an issue with snapper. I can provide the original btrfs disk image (~8MB compressed) if needed for further debugging.

Start by reproducing snapper status 43..47 and snapper diff 43..47 against the two snapshot trees under /mnt/shared/.snapshots/43/snapshot and /mnt/shared/.snapshots/47/snapshot. Compare each reported path with the find . listings; done means status and diff reference only paths that exist and accurately describe the changes.