dovecot - Oct 2011 - setacl fails - does not find dovecot-acl file

Hi,

   I'm using dovecot 2.0.13 that ships with Ubuntu 11.10.
I tried setting up a shared namespace as documented in the wiki to 
enable the sharing of a mailbox between two users.

I have a Maildir(++) directory for each user. Each user has a system 
account. The Maildir of each user is owned by the user's system account
and group read/writable by the group mail (hence mail_access_groups=mail).

Relevant parts of my config:

mail_plugins = acl
mail_location = maildir:/home/dovecot/%u
mail_access_groups = mail

namespace {
   type = private
   separator = /
   prefix    inbox = yes
   hidden = no
   subscriptions = yes
}
namespace {
   type = shared
   separator = /
   prefix = shared/%%u/
   location = maildir:/home/dovecot/%%u:INDEX=/home/dovecot/%u/shared/%%u
   subscriptions = no
   list = children
}

protocol imap {
   mail_plugins = $mail_plugins imap_acl
}

plugin {
   acl = vfile
}
plugin {
   acl_shared_dict = file:/home/dovecot/shared-mailboxes
}

When I try to create an ACL in a telnet session, the command fails with 
an internal error. The log shows:

dovecot: imap(michael): Error: 
fstat(/home/dovecot/michael/.test/dovecot-acl.lock) failed: No such file 
or directory
dovecot: imap(michael): Error: 
file_dotlock_open(/home/dovecot/michael/.test/dovecot-acl) failed: No 
such file or directory

The error occurs whether a (manually created) dovecot-acl file exists or 
not. The dovecot-acl.lock file is created by not removed afterwards.
Subsequent setacl commands will timeout waiting for the lock to be 
released until I delete it manually.

If I create the dovecot-acl file manually and provide access to another 
user, the getacl command will correctly show the permissions and the 
other user can access the folder. setacl will still fail to modify the 
acl file, however (same error).

Another thing that irritates me is that dovecot seems to use the dotlock 
locking method, although I explicitly set lock_method to
fcntl (also tried flock, same behavior).

I'm not using chroot.

I appreciate any help to get this sorted out.

Thanks,
   Michael


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Hi again,

On 22.10.2011 15:16, Michael Stilkerich wrote:
> When I try to create an ACL in a telnet session, the command fails with
> an internal error. The log shows:
>
> dovecot: imap(michael): Error:
> fstat(/home/dovecot/michael/.test/dovecot-acl.lock) failed: No such file
> or directory
> dovecot: imap(michael): Error:
> file_dotlock_open(/home/dovecot/michael/.test/dovecot-acl) failed: No
> such file or directory
  I found that the problem seems to be the try_create_lock_hardlink() 
function, which is used to create the lock file. I don't now why it
doesn't work, but if I modify the code of dotlock_create() to always use 
try_create_lock_excl() instead ignoring the setting of use_excl_lock in 
the dotlock_settings structure, it works just fine for me.

I noticed in the log that the issue not only occurs with the dovecot-acl 
files but with other files, too, namely the
dovecot.index.log and my acl_shared_dict file.

Looking at the static dotlock_settings structure in the acl-file 
backend, I don't see how its use_excl_lock could possible be set to 1 by 
the configuration (i.e., it doesn't seem that the dotlock_use_excl
configuration option is considered). For the maildirlock, an environment 
variable "DOTLOCK_USE_EXCL" is checked instead of the
config setting. I'm not sure whether it is intentional that the hardlink
variant is generally used in these cases.

-Michael

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On Sat, 2011-10-22 at 15:16 +0200, Michael Stilkerich wrote:
> dovecot: imap(michael): Error: 
> fstat(/home/dovecot/michael/.test/dovecot-acl.lock) failed: No such file 
> or directory
This is some weird filesystem? fstat() isn't supposed to ever fail with
ENOENT.
> Another thing that irritates me is that dovecot seems to use the dotlock 
> locking method, although I explicitly set lock_method to
> fcntl (also tried flock, same behavior).
The lock_method setting only affects index files. There are several
others that always use dotlocks, because they're rarely enough modified
that the dotlock performance doesn't matter. That's also why I
haven't
bothered to set use_excl_lock for them.