kern/174310: [zfs] root point mounting broken on CURRENT with multiple pools

[Garrett Cooper]

>Number:         174310
>Category:       kern
>Synopsis:       [zfs] root point mounting broken on CURRENT with multiple pools
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Dec 10 01:10:00 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Garrett Cooper
>Release:        10-CURRENT
>Organization:
n/a
>Environment:
>Description:
I have several zpools in a machine at work and I upgraded from 9.1-STABLE to 10-CURRENT and I can no longer import the pools at boot (run into the mountroot prompt). I am running off a git checkout that's a week or so old, but there aren't any modifications made to sys/boot or sys/cddl/... in my repository in the branch I built the kernel from.

I tried reverting several commits made by avg but I was unable to get my system to boot.

The pool does not show up in the mountroot prompt and if I try to boot from one of gjb's livecds later, it works if the pool is not imported via the kernel first (otherwise zpool status incorrectly claims the pool is faulted). More details are available here: http://permalink.gmane.org/gmane.os.freebsd.current/146313

Will provide more details later (once I get back to work because my system is currently unreachable), but this PR is being filed to track the problem.
>How-To-Repeat:
- Acquire a machine with an mph-based HBA.
- Hook up the spinning disk so it's detected as ada0, the mirrored SSDs as ada1 and ada2 respectively and the L2ARC SSD as ada3.
- Create a pool called root with a spinning disk and an SSD as an L2ARC.
- Create a pool called scratch with 2 SSDs mirrored with one another.
- Install 9.1-RC2 on root.
- Set the bootfs to root.
- Boot the system a few times to make sure it's sane.
- Upgrade to CURRENT as of December 5th.
- Try booting from gjb's livecd, run service hostid onestart, import root to /mnt, run zpool upgrade.
- Try booting again.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: