kern/47020: fss(4) panic

[Manuel.Bouyer%lip6.fr@localhost]

>Number:         47020
>Category:       kern
>Synopsis:       fss(4) panic
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Sep 30 10:40:00 +0000 2012
>Originator:     Manuel Bouyer
>Release:        NetBSD 6.0_RC2
>Organization:
>Environment:
System: NetBSD disco.soc.lip6.fr 6.0_RC2 NetBSD 6.0_RC2 (DISCO) #57: Wed Sep 26 
23:25:27 CEST 2012 
bouyer@houla:/dsk/l1/misc/bouyer/tmp/amd64/obj/dsk/l1/misc/bouyer/netbsd-6/src/sys/arch/amd64/compile/DISCO
 amd64
Architecture: x86_64
Machine: amd64
>Description:
        On a server with some large disks:
/dev/sd0a          188M       149M        30M  83% /
/dev/sd0g          1.9G        56M       1.8G   2% /var
/dev/sd0e          4.8G       1.0G       3.5G  22% /usr
/dev/sd0f           12G       9.5G       2.1G  81% /home
/dev/dk0           5.0T       478G       4.3T   9% /users/disco5
/dev/dk1           5.9T       585G       5.0T  10% /users/disco6
/dev/dk2           1.4T       126G       1.2T   9% /users/disco1
/dev/dk3           1.4T       229G       1.1T  16% /users/disco3
/dev/dk4           445G        48G       375G  11% /users/disco4
         I enabled fsck in the daily run with snapshots: in /etc/daily.conf
run_fsck=YES run_fsck_flags="-Tffs:-x/users/disco5/"

        (this means that all filesystems are checked on an external
         snapshot, exept /users/disco5).
        The following night it paniced with (restored from the mess printed
on console created by all the "WARNING SPL NOT LOWERED ON SYSCALL EXIT"
messages mixed with the real panic message - I may have missed something,
or mixed numbers):
panic: kernel diagnostic assertion  "vp ==  vp->v_specnode->sn_dev->sd_bdevvp"  
failed: file /dsk/l1/misc/bouyer/netbsd-6/src/sys/miscfs/specfs/spec_vnops.c", 
line 757    
cpu23:  begin traceback...        
kern_assert at netbsd:: kern_assert+0x48      
spec_ioctl at netbsd :spec_ioctl+0x101    
VOP_IOCTL at netbsd:VOP_IOCTL+0x33b                                        
getdisksize at netbsd: :get disksize+0x47  
fss_ioctl at  netbsd:fss_ioctl+0x50f 
vn_ioctl at netbsd:vn_ioctl+0x76     
sys_ioctl() at netbsd:sys_ioctl+0xc7

There was probably some NFS activity running at the same time,
as well as some amanda dumps (running without snapshots).

>How-To-Repeat:
        I did run the fsck -x by hand several times before enabling it in
        rc.conf, and didn't see this problem. So I guess other factors are
        needed, maybe the dump running, or some other FS activity
>Fix: