sis deduplication broken from 2.2.16 upwards

[Alexander Moisseev]

On 11.03.16 3:56, Timo Sirainen wrote:
>
>> On 11 Mar 2016, at 02:37, Charles Marcus <CMarcus at Media-Brokers.com> wrote:
>>
>> On 3/9/2016 9:02 PM, Timo Sirainen <tss at iki.fi> wrote:
>>> On 08 Mar 2016, at 01:50, Pavel Stano <stanojr at websupport.sk> wrote:
>>>>
>>>> sis attachment deduplication is broken in 2.2.16 upwards.
>>>> It is caused by this commit.
>>>> https://github.com/dovecot/core/commit/664bf3e236c214aee86294483c379e4fa66c2e63
>>>>
>>>> in src/lib-fs/fs-sis.c function fs_sis_try_link() is comparation of
>>>> inodes of hash files.
>>>> Because fs_stat() after that commit use fstat() on open fd of temporary
>>>> file instead of stat on filename. But that temporary file has differnt
>>>> inode.
>>>>
>>>> It not cause any corruption but it will not save any space.
>>>> Because every duplicate attachment will be in separate file.
>>> Thanks, fixed: https://github.com/dovecot/core/commit/3b39022ea0513363241cf852b7d454c841584ea1
>>
>> So, after the fix is applied, does dovecot silently delete the
>> duplicated files, or is there a command that needs to be run manually?
>
> You'd have to do it manually in some way. A script that does something like:
>
> Go through all attachment directories and for each file:
>  - Sort files by filename
>  - Identify that files A and B the same (beginning of the filename begins with same hash), but have a different inode
>  - ln A B.tmp && mv B.tmp B
>
  
I've also found that many of /hashes/ directories have missed.

# ll /tank1/vmail/attachments/1f/1f
total 3300
-rw-------  1 vmail  vmail   403976 12 ноя 00:20 1f1f504c582600a2af94b39c088692aba714fe72-c53b9e1508b14356797d0100d09efc50
-rw-------  1 vmail  vmail   403976 12 ноя 00:20 1f1f504c582600a2af94b39c088692aba714fe72-c93b9e1508b14356797d0100d09efc50
-rw-------  1 vmail  vmail   403976 12 ноя 00:20 1f1f504c582600a2af94b39c088692aba714fe72-f2a777181eb14356807d0100d09efc50
-rw-------  1 vmail  vmail   403976 12 ноя 00:20 1f1f504c582600a2af94b39c088692aba714fe72-f31a5e2917b143567e7d0100d09efc50
-rw-------  1 vmail  vmail  2582016  3 ноя 00:20 1f1f97880e8cddc2dfe3c4ad2654b9da937226b7-94c53d358bd33756d6140000d09efc50

Is it related to the same bug or there is another issue?
Is it safe to delete attachment files if there is no file with the same hash in the /hashes/ directory or there is no /hashes/ directory at all?