[Dovecot] Corrupted mboxes with v2.2.4, posix_fallocate and GFS2

[Timo Sirainen]

On 5.8.2013, at 19.46, Francesco Prelz <Francesco.Prelz at mi.infn.it> wrote:

> on a clustered Dovecot server installation that was recently moved from a
> shared GPFS filesystem to GFS2, occasional corruptions in the users'
> INBOXes started appearing, where a new incoming message would be appended directly after a block of NUL bytes, and be scanned by dovecot as being
> glued to the preceding message.
> 
> I traced this to the file extension operation performed in
> mbox_sync_handle_eof_updates, where the 'file_set_size' call
> is used. If available, file_set_size will use the posix_fallocate
> call. In GFS2 posix_fallocate increases the file size in 4 kB chunks
> (there seems to be no guarantee anyway that posix_allocate will
> extend a file by the exact size requested).

I think that's a bug in GFS2. I understand posix_fallocate() man page to clearly say that it grows the file to the specified offset+len, not any higher. So could be a good idea to report it to their developers if they're not aware of it..

Anyway, I thought I'd just get rid of the whole syscall since it's not very useful anyway: http://hg.dovecot.org/dovecot-2.2/rev/42b2736f146b