kern/154860: [gmirror] [panic] geom_mirror panices system on specific sector contents

[Eugene Grosbein]

>Number:         154860
>Category:       kern
>Synopsis:       [gmirror] [panic] geom_mirror panices system on specific sector contents
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Feb 18 09:20:10 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Eugene Grosbein
>Release:        FreeBSD 8.2-PRERELEASE amd64
>Organization:
RDTC JSC
>Environment:
System: FreeBSD k-45-pc-1.sd.rdtc.ru 8.2-PRERELEASE FreeBSD 8.2-PRERELEASE #20: Fri Feb 18 13:08:00 NOVT 2011 root at k-45-pc-1.sd.rdtc.ru:/usr/local/obj/home/src/sys/PPPOE amd64

>Description:
	My 8.2-PRERELEASE/amd64 system has two HDDs:
	ad8 and ad14 having equal sector number:

# atacontrol cap ad8

Protocol              SATA revision 2.x
device model          WDC WD3200AAJS-00L7A0
serial number         WD-WMAV2DP22862
firmware revision     01.03E01
cylinders             16383
heads                 16
sectors/track         63
lba supported         268435455 sectors
lba48 supported       625142448 sectors

	Both disks were combined to one gmirror /dev/mirror/gm0.
	After unclean system shutdown this mirror became dirty
	and started rebuilding process from ad8 to ad14.
	Meantime, background fsck started to repair /usr/local
	and /home simultaneously (they are mounted in fstab by UFS labels).

	I/O contention was high so I decided to remove ad14 from the mirror
	to speedup fsck hoping reinsert ad14 to the mirror later:

gmirror remove gm0 ad14

	Immediately I've got kernel panic and system rebooted at once.
	Then it paniced again just at the moment of gmirror initialization.
	And again, and again... So I was forced to use loader
	to disable loading of geom_mirror.ko and go to single user mode
	mounting root from ad14.

	I've attempted to load geom_mirror.ko from single user mode
	and it panices the system at once.

	So I've saved contents of last sector of ad8 and ad14 to files.
	Last sector of ad14 contained only zero bytes. Last sector of ad8
	comes here gzipped and uuencoded.

begin 644 sector.gz
M'XL(`&8G7DT``W-W]?>ULO+U#`KR#V+X__\_"P,#0WJN`4,QIV$#D/L_8=>A
M!;_E+R\I/!>6S at B48P`3#`(,#$P,<5=;O4`<)A!1=H6%`0&8&'"`!(B>RR^8
<MW]9=E';:`-?=&/LV:,,HV!@``"LL=3X``(`````
`
end

	Then I've erased this sector with zeroes and this allowed
	me to load geom_mirror.ko without following panic
	and recreate my mirror.

>How-To-Repeat:

1. Perform unclean shutdown of system booting from gmirror to make it dirty.
2. After reboot, remove dirty component of gmirror (this paniced my system).
3. Then geom_mirror panices all the time until its signature erased from HDD.

>Fix:

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