Date: Fri, 21 Feb 2003 15:26:01 -0800
From: Terry Lambert <[EMAIL PROTECTED]>
To: Yevgeniy Aleynikov <[EMAIL PROTECTED]>
CC: Kirk McKusick <[EMAIL PROTECTED]>,
Matt Dillon <[EMAIL PROTECTED]>,
Ian Dowse <[EMAIL PROTECTED]>,
[EMAIL PROTECTED], [EMAIL PROTECTED],
Ken Pizzini <[EMAIL PROTECTED]>,
[EMAIL PROTECTED], [EMAIL PROTECTED],
[EMAIL PROTECTED],
[EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED],
[EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED]
Subject: Re: bleh. Re: ufs_rename panic
Yevgeniy Aleynikov wrote:
> As pointed by Ken - we do have alot of file renames (qmail).
> But 2-nd solution, directory-only rename serialization, probably
> won't affect performance as much.
>
> But i believe it's not only us who's gonna have problem when exploit
> code will be known by everybody sooner or later....
Dan's non-atomicity assumption on renames is incorrect.
Even if it's were correct, it's possible to recover fully following
a failure, because metadata updates are ordered (there is a real
synchronization between dependent operations).
I think that a workaround would be to comment the directory fsync()
code out of qmail, which apparently thinks it's running on extfs
or an async mounted FFS.
-- Terry
You cannot get rid of the fsync calls in qmail. You have to distinguish
between a filesystem that is recoverable and one which loses data.
When receiving an incoming message, SMTP requires that the receiver
have the message in stable store before acknowledging receipt. The
only way to know that it is in stable store is to fsync it before
responding.
Kirk McKusick
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