i386/144214: zfsboot fails on gang block after upgrade to zfs v14

[Volodymyr Kostyrko]

>Number:         144214
>Category:       i386
>Synopsis:       zfsboot fails on gang block after upgrade to zfs v14
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Feb 22 20:50:01 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Volodymyr Kostyrko
>Release:        RELENG_8
>Organization:
>Environment:
FreeBSD limbo.lan 8.0-STABLE FreeBSD 8.0-STABLE #0: Sun Feb 21 13:49:54 EET 2010     arcade at limbo.lan:/usr/obj/usr/src/sys/MINIMAL_8  i386
>Description:
The bug is hard to get. Everything should match:

 * i386 arch,
 * `make installkernel`,
 * RELENG_8 after zfs v14 import,
 * zpool with zfs v14,
 * zfsboot installed.

Boot partition is NOT compressed, changing the boot partition does nothing, even creating a new one.

After that sometimes part of kernel or other modules would yield "ZFS: gang block detected" on loading.
>How-To-Repeat:
Any installkernel can do the trick.
>Fix:
Bootability can be restored with:

rsync -lrptygoWSH --delete /boot /somewhere/boot
rm -rf /boot
rsync -lrptygoWSH --delete /somewhere/boot /boot

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