[Dovecot] POP (dot) locks

[Timo Sirainen]

On Tue, 2004-05-18 at 15:10, Christian Balzer wrote:
> # Should we create dotlock file even when we want only a read-lock? Setting
> # this to yes hurts the performance when the mailbox is accessed simultaneously
> # by multiple processes, but it's needed for reliable reading if no other
> # locking methods are available.
> #mbox_read_dotlock = no
> ---
> means that if the only other reading accesses to a (mbox style in this
> case here) mailbox are via other dovecot processes everything will be fine?

This setting only means that we use dotlock also for read-locking, not
just write-locking mbox. Normally it uses just fcntl/flock. Hmm. I think
I should change the description a bit.

So, currently Dovecot doesn't try to lock mbox for the whole POP3
session. That may create problems if two sessions actually try to access
the mailbox concurrently. If message gets expunged by another process,
Dovecot replies with -ERR to requests to fetch the message. That might
confuse some POP3 clients, or cause them to send errors to user.

I don't think normally anyone even tries concurrent POP3 access? Anyway,
I have thought before that Dovecot/pop3 should lock the mbox for the
whole time, just like all others POP3 servers do (and RFC says too)..
I'll add in TODO.

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