QMail and SoftUpdates

David Schultz das at FreeBSD.ORG
Tue May 18 03:13:40 PDT 2004

On Mon, May 17, 2004, Don Lewis wrote:
> Based on the information I found using Google, it appears that qmail
> relies on link(2) being synchronous to let it know that a queued message
> is safely on the disk with a known file name before it issues the "250"
> response. I believe this was true without softupdates, but with
> softupdates enabled it is definitely not true.

If this is true, it's a boog in qmail[1].  The link(2) syscall
guarantees atomicity, but not durability.  This is why fsync(2)

[1] I would call it a ``bug'', but then I would be uttering one of
    the magic phrases to invoke djb in a public forum.

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