[Dovecot] attachment sis + EMLINK (too many links) = segfault bug (2.2.12)

[Pavel Stano]

Hi,

we use attachment dedup with lots of emails (still migrating to it
from maildir).
We use netapp storage with wafl filesystem over nfs.
Problem is that netapp has hard limit of 100k hardlinks to one file.
And we encountered it.

Problem is that dovecot start do segfault (lmtp,dsync,pop3 etc) when it
happend when tried to deliver new emails with that attachment.
Here is strace of dsync:

6740
link("/nfsmnt/mailatch1/f9/10/hashes/f9108ddaa156ac15738e41ed3bedec1eda50175d",
"/nfsmnt/mailatch1/f9/10/f9108ddaa156ac15738e41ed3bedec1eda50175d-7bb7a20ddb598853541a000028db4a9f")
= -1 EMLINK (Too many links) 6740  --- SIGSEGV (Segmentation fault) @ 0
(0) ---

ls -lh:
-rw------- 100000 vmail vmail 4.7K Apr 28
16:54 /nfsmnt/mailatch1/f9/10/hashes/f9108ddaa156ac15738e41ed3bedec1eda50175d

We were using mail_attachment_min_size=4kb, we solve it by increasing it
to 8kb.

It would be nice to somehow fix this problem. Like not crash when
EMLINK happend and maybe do not deduplicate attachments but deliver
email without dedup.
Or create second file in hashes/ and start hardlinking it instead of
original.

AFAIK ext4 has also hard-link limit 64k
(http://en.wikipedia.org/wiki/Hard_link#Limitations_of_hard_links)
So this can happen to anyone with lots of emails.

Thanks
-- 
[ Ohodnotte kvalitu mailu: http://nicereply.com/websupport/Stano/ ]

Pavel Stano | Troubleshooter

http://WebSupport.sk
*** BERTE A VYCHUTNAVAJTE ***

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