lofi mount [PSARC/2008/290 FastTrack timeout 05/06/2008]

[John Levon]

On Sun, May 04, 2008 at 02:47:24AM -0700, Dan Price wrote:

> It would be nice if this proposal fit in with that scheme; that is, with your
> proposed new capability, I'd also assume that I could now do the following?

Good questions.

> zonecfg:foo> add fs
> zonecfg:foo:fs> set dir=/mnt
> zonecfg:foo:fs> set special=/export/my.iso
> zonecfg:foo:fs> set type=hsfs
> zonecfg:foo:fs> add options ro
> zonecfg:foo:fs> end

I agree that this should work, but zoneadm isn't ready yet:

- it uses stat() not stat64() on the special device
- for other than hsfs, it insists upon a raw device

The former is (presumably) a simple fix. The latter is trickier: we
don't have a raw device to fsck. Perhaps zoneadm shouldn't be insisting
on a fsck pass anyway, or maybe this just shouldn't be allowed. What do
you think?

> Two final questions: (1) is there any potential interaction with fsck(1m)
> here?  In other words, if the file we're looping back represents an FS
> which requires an fsck stage, how will that work?

Exactly like it does with lofiadm+mount today (or any direct mount
invocation): it'll mount without checking.

>  (2) Will the lofi nodes created in this manner be visible in the
>  output of lofiadm(1m)?

Yes. I did toy with an alternative where it won't appear in /devices/,
but it was not nice implementation-wise, and after some thought felt
that listing the lofi entries was the right thing to do anyway.

regards
john