amd64/122173: Kernel Panic if attempting to replace a drive in a raidz wih zfs

[Alex Frangis]

>Number:         122173
>Category:       amd64
>Synopsis:       Kernel Panic if attempting to replace a drive in a raidz wih zfs
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Mar 28 00:30:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Alex Frangis
>Release:        Freebsd 7.0
>Organization:
>Environment:
FreeBSD isajeep 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Sun Feb 24 10:35:36 UTC 2008     root at driscoll.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

>Description:
When replacing a dead drive in a ZFS array, if the new drive comes up on the same identifier (ad6) as the drive that died and you issue the command "zpool tank replace ad6 ad6" to tell zfs to replace the missing drive with the new drive, ZFS starts the reslivering process and then promptly induces a kernel panic.
>How-To-Repeat:
1. Create a raidz
2. Degrade one drive in the raidz
3. Replace with another drive attached to the same channel so that the replacement drive comes up as the same identifier (i.e. dead drive is /dev/ad6 and new drive comes up as /dev/ad6)
4. Attempt to issue replace command. 
>Fix:
Move the replacement drive such that its identifier is something other than the one of the dead drive and ZFS will complete rebuilding the array. 

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