Inbox quota usage doubled when mailbox_list_index enabled, under some circumstances

[Chris Dillon]

I’ve had the opportunity to test the same configuration with a fresh build of the git master branch (2.4.devel) and the issue also occurs there.  I see that "mailbox_list_index = yes" is now enabled by default.  It can still be disabled via "mailbox_list_index = no" which allows the quota to be calculated correctly.

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root at ubuntu1804:~# dovecot -n
# 2.4.devel (44282aeeb): /usr/local/etc/dovecot/dovecot.conf
# OS: Linux 4.15.0-30-generic x86_64 Ubuntu 18.04.1 LTS 
# Hostname: ubuntu1804
mail_location = maildir:~/Maildir
mail_plugins = quota
namespace inbox {
  inbox = yes
  location = 
  prefix = INBOX.
  separator = .
}
passdb {
  driver = pam
}
plugin {
  quota = maildir:Mailbox
}
userdb {
  driver = passwd
}
==========

(To summarize from my previous message -- other than "mailbox_list_index = yes", second most important part of replication is that there is at least one email in the real inbox and at least one sub-folder named "INBOX" in maildir format)

root at ubuntu1804:~# ls -ld /home/myuser/Maildir/cur/1532529376.M543965P58007.centos7.local\,S\=12712627\,W\=12877782\:2\,S /home/myuser/Maildir/.INBOX.Test/ 
-rw-rw-r-- 1 myuser myuser 12712627 Aug 14 18:28 '/home/myuser/Maildir/cur/1532529376.M543965P58007.centos7.local,S=12712627,W=12877782:2,S'
drwxrwxr-x 5 myuser myuser       87 Aug 14 18:56  /home/myuser/Maildir/.INBOX.Test/
=========

(In the following example usage is doubled, there is only one email)

root at ubuntu1804:~# doveadm quota recalc -u myuser; doveadm quota get -u myuser
Quota name Type    Value Limit                                                              %
Mailbox    STORAGE 24830     -                                                              0
Mailbox    MESSAGE     2     -                                                              0
==========

(In the following example it works correctly with mailbox_list_index disabled)

root at ubuntu1804:~# doveadm -o 'mailbox_list_index=no' quota recalc -u myuser; doveadm quota get -u myuser
Quota name Type    Value Limit                                                              %
Mailbox    STORAGE 12415     -                                                              0
Mailbox    MESSAGE     1     -                                                              0
==========

Best Regards