vdrain/cache trap panics on NetBSD/amd64-7.0_STABLE

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

Every so often, my file server panics and reboots--which it did
just a few hours ago.  The saved core reports, via 'crash':

$ crash -N netbsd.6 -M netbsd.6.core
Crash version 7.0_STABLE, image version 7.0_STABLE.
System panicked: trap
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NAGR() at 0
_KERNEL_OPT_NAGR() at 0
vpanic() at vpanic+0x145
snprintf() at snprintf
startlwp() at startlwp
calltrap() at calltrap+0x11
cache_purge1() at cache_purge1+0x10f
vclean() at vclean+0xa8
cleanvnode() at cleanvnode+0xd0
vdrain_thread() at vdrain_thread+0x58
crash>

The previous occasion (29 July 2016) showed:

$ crash -N netbsd.5 -M netbsd.5.core 
Crash version 7.0_STABLE, image version 7.0_STABLE.
System panicked: trap
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NAGR() at 0
_KERNEL_OPT_NAGR() at 0
vpanic() at vpanic+0x145
snprintf() at snprintf
startlwp() at startlwp
calltrap() at calltrap+0x11
cache_reclaim() at cache_reclaim+0x201
cache_thread() at cache_thread+0x15

Before that, (25 Dec 2015):

$ crash -N netbsd.4 -M netbsd.4.core 
Crash version 7.0_STABLE, image version 7.0_STABLE.
System panicked: trap
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NAGR() at 0
_KERNEL_OPT_NAGR() at 0
vpanic() at vpanic+0x145
snprintf() at snprintf
startlwp() at startlwp
calltrap() at calltrap+0x11
uvm_pagefree() at uvm_pagefree+0xd4
genfs_do_putpages() at genfs_do_putpages+0xce0
VOP_PUTPAGES() at VOP_PUTPAGES+0x3a
uvm_pageout() at uvm_pageout+0x2f1

and before that (7 Nov 2015):

$ crash -N netbsd.3 -M netbsd.3.core 
Crash version 7.0_STABLE, image version 7.0_STABLE.
System panicked: trap
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NAGR() at 0
_KERNEL_OPT_NAGR() at 0
vpanic() at vpanic+0x145
snprintf() at snprintf
startlwp() at startlwp
calltrap() at calltrap+0x11
ufsquota_free() at ufsquota_free+0x15
ufs_reclaim() at ufs_reclaim+0xaf
ffs_reclaim() at ffs_reclaim+0xa1
VOP_RECLAIM() at VOP_RECLAIM+0x2f
vclean() at vclean+0xa6
cleanvnode() at cleanvnode+0xb8
vdrain_thread() at vdrain_thread+0x58

And the earliest I have saved (6 Nov 2015):

$ crash -N netbsd.2 -M netbsd.2.core 
Crash version 7.0_STABLE, image version 7.0_STABLE.
System panicked: trap
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NAGR() at 0
_KERNEL_OPT_NAGR() at 0
vpanic() at vpanic+0x145
snprintf() at snprintf
startlwp() at startlwp
calltrap() at calltrap+0x11
VOP_PUTPAGES() at VOP_PUTPAGES+0x3a
uvm_pageout() at uvm_pageout+0x2f1


Anyone else see anything like this?  What other information from
the crash dumps would be useful?

The system runs a RAIDframe RAID-R across 8 1TB SATA disks with a
single filesystem.  It also serves as slave DNS and NTP.

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