Author: Merlin Hartley Date: To: Nigel Metheringham CC: Andrew C Aitchison, exim-users, Jeremy Harris Subject: Re: [exim] Exim, Dovecot, mdir and hardlinks - a true story
More generally isn’t it easier to let the imap system manage the quotas and the mta just queries that? The imap would need to enforce them anyway and allow mua to query it...
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Merlin Hartley
> On 14 Aug 2019, at 17:20, Nigel Metheringham via Exim-users <exim-users@???> wrote:
>
> Would not taking the quota size of a message as being the file size / link count be good enough?
>
> If there are links between users then this will underestimate the size of a maildir structure, but in general it would be right.
>
> But it does force a stat() call which the put everything in the name as tags was designed to avoid - we used to really want that way back in the days of huge numbers of users with NFS mounted mailboxes in late 90's ISPs.
>
> Nigel.
>
> Andrew C Aitchison via Exim-users wrote on 14/08/2019 16:48:
>>> On Wed, 14 Aug 2019, Jeremy Harris via Exim-users wrote:
>>>
>>>> On 14/08/2019 12:37, Andrew C Aitchison via Exim-users wrote:
>>>> I suspect an option to have a fast but inaccurate quota would be useful
>>>> in some circumstances.
>>>
>>> We already have maildir_use_size_file; rebuilding isn't needed often.
>>>
>>> Do we need a fast/poor quota method for cases where the size-file
>>> cannot be used?
>>
>> Ah. I had missed that Cyborg is using maildir format (I'm used to mbox).
>>
>>> Other possible ways of balancing: we currently glance at the filename,
>>> trying to pull a size encoded in it. That saves an additional per-file
>>> stat call to get the size. But without the stat we don't have an
>>> inode number... we can hash the filename, but that only works if
>>> a hardlink is to a different dir but with the same name. We could
>>> glance at the number of links, and only bother remembering >1 link
>>> nodes - but, again, we then need to do the stat call.
>>
>> From the introduction to "Chapter 26 - The appendfile transport":
>> Exim recognizes system quota errors, and generates an appropriate
>> message. Exim also supports its own quota control within the transport,
>> for use when the system facility is unavailable or cannot be used for some reason.
>>
>> Now I think about it I've not (knowingly) used both on the same filesystem.
>> I also now realize that the INBOX and the files that a .forward file
>> redirects mail to may be on different disks and have different quotas ...
>>
>
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