kern/133614: panic: ffs_truncate: read-only filesystem

[Mikhail T.]

>Number:         133614
>Category:       kern
>Synopsis:       panic: ffs_truncate: read-only filesystem
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Apr 11 21:30:04 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Mikhail T.
>Release:        FreeBSD 7.2-PRERELEASE amd64
>Organization:
Virtual Estates, Inc. http://libpipe.com/
>Environment:
System: FreeBSD aldan.algebra.com 7.2-PRERELEASE FreeBSD 7.2-PRERELEASE #2: Thu Apr 9 06:23:59 EDT 2009 root at aldan.algebra.com:/var/src/sys/amd64/compile/SILVER-SMP amd64

>Description:
	Hello! I have a filesystem, that is mounted read-only by
	default:

/dev/ad10		/ad10		ufs	ro		0	1

	It is holding data, that's modified infrequently and I thought,
	keeping it RO most of the time will be safer.

	I had to add a few (large) files recently and remounted the FS
	in read-write mode. "To be sure", I did an umount, fsck, and
	rw-mount:

		umount /ad10
		fsck -y /ad10	# No errors reported by fsck
		mount -orw /ad10
		mount	# See /ad10 mounted as (ufs, local, soft-updates)

	When I then proceeded to write to the filesystem (via Samba),
	the system paniced as follows:

Unread portion of the kernel message buffer:
panic: ffs_truncate: read-only filesystem
cpuid = 3
Uptime: 35m50s
Physical memory: 5911 MB
Dumping 519 MB: 504 488 472 456 440 424 408 392 376 360 344 328 312 296 280 264 248 232 216 200 184 168 152 136 120 104 88 72 56 40 24 8Attempt to write outside dump device boundaries.

** DUMP FAILED (ERROR 6) **
Automatic reboot in 15 seconds - press a key on the console to abort
fs = /ad10
panic: ffs_sync: rofs mod
cpuid = 3
Rebooting...
cpu_reset: Stopping other CPUs
Uptime: 36m33s
Physical memory: 5911 MB
Dumping 519 MB: 504 488 472 456 440 424 408 392 376 360 344 328 312 296 280 264 248 232 216 200 184 168 152 136 120 104 88 72 56 40 24 8

Reading symbols from /opt/modules/rtc.ko...done.
Loaded symbols for /opt/modules/rtc.ko
#0  doadump () at pcpu.h:195
195		__asm __volatile("movq %%gs:0,%0" : "=r" (td));
(kgdb) 

	Please, advise... Thanks!

>How-To-Repeat:

>Fix:

	I suppose, I could just be mounting it RW from the beginning,
	but it was certainly nicer to be able to switch to/from RW
	on the fly...


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