Dovecot v2.3.13 reporting (very) incorrect vsize for some maildir folders

[Timo Sirainen]

On 5. May 2021, at 15.42, Eirik Rye <rye at trojka.no> wrote:
> 
> Afterwards, for a couple users, we received reports that mail delivery had failed because they were over quota. When looking into it for a specific user, we noticed that the vsize reported for a particular folder (with 47k messages) was reported as being nearly 50 times larger than it's on-disk size:
> 
> root at mail02:~# doveadm mailbox status -u anonymized_user 'messages recent unseen vsize' 'anonymized/folder/name'
> [...]
> anonymized/folder/name messages=47338 recent=0 unseen=0 vsize=14335366070
> 
> However, the filesystem itself reports a much smaller size (but correct message count):
> 
> root at mail02:~# du -hd1 /home/anonymized_user/Maildir/.anonymized.folder.name/
> 313M    /home/anonymized_user/Maildir/.anonymized.folder.name/cur
> 36K     /home/anonymized_user/Maildir/.anonymized.folder.name/tmp
> 4.0K    /home/anonymized_user/Maildir/.anonymized.folder.name/new
> 320M    /home/anonymized_user/Maildir/.anonymized.folder.name/
> 
> root at mail02:~# ls /home/anonymized_user/Maildir/.anonymized.folder.name/cur | wc -l
> 47338
> 
> I have tried:
> 
>  - `doveadm force-resync -u anonymized_user`
>  - deleting the index files in the specific folder, and running `doveadm index -u anonymized_user '*'` as well as `doveadm mailbox status -u anonymized_user vsize '*'`
>  - deleting all `*index*` files in maildir, and running `doveadm index -u anonymized_user '*'` as well as `doveadm mailbox status -u anonymized_user vsize '*'`
>  - comparing all maildir-sizes (S=) with their actual sizes to see if there are discrepancies. There are none.

S= is the "physical size", W= is the "virtual size". quota=count / vsize calculations should be using the W= value, not the S= value.

> Even after deleting the list index (dovecot.list.index) as well as the mailbox indexes, recalculating the vsize seems very quick so I feel like the incorrect vsize is being fetched from a cache somewhere instead of being recalculated..?

The sizes can also be stored in dovecot-uidlist.