softdep as a mount(8) option

[Stefan Esser]

Am 29.10.17 um 00:25 schrieb Kirk McKusick:
>> Date: Fri, 27 Oct 2017 11:39:00 -0400
>> From: Mark Johnston <markj at FreeBSD.org>
>> To: freebsd-fs at FreeBSD.org
>> Subject: softdep as a mount(8) option
>>
>> Hi,
>>
>> I'd like to finally enable the use of SU (not SU+J) on some small UFS
>> filesystems. The fact that SU is enabled using a flag in the superblock
>> poses a problem for me, however: the systems containing these
>> filesystems may at any time be repurposed to run a kernel that supports
>> SU but contains bugs[*] that render it unusable. I therefore can't
>> persistently enable SU in these systems.
>>
>> I'm wondering if it would be possible to enable SU using a mount
>> option rather than with a persistent flag. fsck_ffs conditionalizes some
>> of its logic on whether SU is configured - is this necessary for
>> correctness? That is, if I run fsck on an unclean filesystem that had
>> been mounted with SU, and fsck runs as though SU hadn't been configured,
>> what problems might arise?
>>
>> [*] These bugs are a result of local modifications and aren't in
>> FreeBSD.
> 
> While it is safe and possible to add soft-updates (but not journalled
> soft updates) as a mount option, it means that fsck will not know that
> soft updates were in use, so it will always run in full (slow) mode at
> boot time. This is why I have not added it as an option.

Hi Kirk,

this is a link to the message where you agreed to make SU a mount option:

	http://docs.freebsd.org/cgi/mid.cgi?200006282051.NAA05776

Seems you were (rightly) not too worried about FSCK, back then ;-)

Regards, STefan