inaccessible hard links are stored

[ThomasWaldmann]

similar to: jborg/attic#393

$ touch hl1
$ chmod 000 hl1
$ ln hl1 hl2
$ borg create repo::hl-check .
hl1: [Errno 13] Permission denied: 'hl1'
$ mkdir extract
$ cd extract
$ borg extract ../repo::hl-check
hl2: [Errno 2] No such file or directory: '/home/tw/w/borg/extract/hl1' -> '/home/tw/w/borg/extract/hl2'
$ ls -l hl*
ls: cannot access 'hl*': No such file or directory
$ borg list ../repo::hl-check | grep hl
h--------- tw     tw            0 Sat, 2017-01-21 20:08:04 hl2 link to hl1

[ThomasWaldmann]

Also:

(borg-env)tw@tux:~/w/borg/extract$ borg mount ../repo::hl-check mnt
Enter passphrase for key /home/tw/w/borg/repo: 
Local Exception.
Traceback (most recent call last):
  File "/home/tw/w/borg/borg/archiver.py", line 2076, in main
    exit_code = archiver.run(args)
  File "/home/tw/w/borg/borg/archiver.py", line 2012, in run
    return func(args)
  File "/home/tw/w/borg/borg/archiver.py", line 91, in wrapper
    return method(self, args, repository=repository, **kwargs)
  File "/home/tw/w/borg/borg/archiver.py", line 560, in do_mount
    operations = FuseOperations(key, repository, manifest, archive, cached_repo)
  File "/home/tw/w/borg/borg/fuse.py", line 71, in __init__
    self.process_archive(archive)
  File "/home/tw/w/borg/borg/fuse.py", line 139, in process_archive
    inode = self._find_inode(item[b'source'], prefix)
  File "/home/tw/w/borg/borg/fuse.py", line 182, in _find_inode
    inode = self.contents[inode][segment]
KeyError: b'hl1'

Platform: Linux tux 4.9.4-tw2 #1 SMP Wed Jan 18 07:03:50 CET 2017 x86_64 x86_64
Linux: Ubuntu 16.04 xenial
Borg: 1.0.10.dev80+ngca0c1da  Python: CPython 3.5.2
PID: 22263  CWD: /home/tw/w/borg/extract
sys.argv: ['/home/tw/w/borg-env/bin/borg', 'mount', '../repo::hl-check', 'mnt']
SSH_ORIGINAL_COMMAND: None

[enkore]

• Correct create code
• Add proper error handling to mount
• extract fails on the item and so does approximately the right thing by extension.

[ThomasWaldmann]

If we skip hl1, we should also skip hl2. Hardlinks are symmetric. No problem with extract and mount then.

[enkore]

Since there is still #1297 it has to be handled in mount. This is also just a variation on #1297, just that the master backup does not fail due to a lost race, but due to lack of permissions.

[ThomasWaldmann]

Fixed by #2094.