dovecot - Jul 2013 - Non-blocking file_dotlock_open() in quota-maildir question

Hello,

Is it safe to change lines in plugins/quota/quota-maildir.c::maildirsize_write()
from
? fd = file_dotlock_open_group(.., DOTLOCK_CREATE_FLAG_NONBLOCK, ..);
to
? fd = file_dotlock_open_group(.., 0, ..); ?

Rationale is: exim+cpanel frequently leave stale maldirsize.lock, but when quota
plugin try to dotlock maildirsize, it do this with NONBLOCK flag and just once,
so first lock fails with EAGAIN and second may never happen. (When last mail is
over quota this also prevent user from further receiving any mail because quota
remain exceeded, forver. This is annoing problem.) I wonder if it is possible to
do easy fix problem by removing NONBLOCK flag, but as I don't understand why
this NONBLOCK flag is used in the first place I decided to ask developers in the
list for approval.

If removing NONBLOCK flag is not possible I will just call
file_dotlock_open_group() twice if first one return -1 with EAGAIN.

Best regards,
Don.

On Mon, 2013-07-08 at 22:42 +0400, do1 at yandex.ru
wrote:
> Hello,
> 
> Is it safe to change lines in
plugins/quota/quota-maildir.c::maildirsize_write() from
>   fd = file_dotlock_open_group(.., DOTLOCK_CREATE_FLAG_NONBLOCK, ..);
> to
>   fd = file_dotlock_open_group(.., 0, ..); ?
> 
> Rationale is: exim+cpanel frequently leave stale maldirsize.lock, but when
quota plugin try to dotlock maildirsize, it do this with NONBLOCK flag and just
once, so first lock fails with EAGAIN and second may never happen. (When last
mail is over quota this also prevent user from further receiving any mail
because quota remain exceeded, forver. This is annoing problem.) I wonder if it
is possible to do easy fix problem by removing NONBLOCK flag, but as I don't
understand why this NONBLOCK flag is used in the first place I decided to ask
developers in the list for approval.
Here's a better fix: http://hg.dovecot.org/dovecot-2.2/rev/24d6708cea76