Re: Snapshot cannot be deleted

[Filipe David Manana <fdmanana@gmail.com>]

On Tue, Jan 20, 2015 at 12:28 PM, Andreas Philipp
<philipp.andreas@gmail.com> wrote:
> Hi,
>
> Due to the known (and fixed) bug in kernel 3.17.0 one of my btrfs
> volume suffers from unreadable and - even worse - uneraseable
> snapshots. Whenever such a snapshot is accessed there is "parent
> transid verify failed" in dmesg.
> Is there any way to delete these snapshots?

It can be fixed with btrfs-progs v3.17 and later (3.18.x is the latest release).
To confirm that you are affected by the 3.17 kernel issue, run btrfsck
in readonly mode first (without --repair or any other flags), which
will print one message with the following format for each corrupt
snapshot:

"root %llu has a root item with a more recent gen (%llu) compared to
the found root node (%llu)\n"

Any other error messages are likely unrelated and therefore associated
with other eventual issues.
As usual, before running btrfsck with --repair (which fixes the issue
and the snapshots will be fully repaired), create backups of your
data.

Hope it helps.

>
> Thanks,
> Andreas
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-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."