stab;e/10 panic under disk load

[Dmitry Morozovsky]

Dear colleagues,

my backup server after updrade to frest stable/10

start panicing on heavy disk load like rsync at

FreeBSD whale.rinet.ru 10.1-STABLE FreeBSD 10.1-STABLE #195 r274646: Tue Nov 18 
12:15:24 MSK 2014     
marck at castor.rinet.ru:/usr/obj/FreeBSD/pristine/src.10/sys/GENERIC  amd64


panic: vm_fault: fault on nofault entry, addr: fffffe001805b000
cpuid = 0
KDB: stack backtrace:
#0 0xffffffff80964fa0 at kdb_backtrace+0x60
#1 0xffffffff8092a085 at panic+0x155
#2 0xffffffff80ba168e at vm_fault_hold+0x1b6e
#3 0xffffffff80b9fad7 at vm_fault+0x77
#4 0xffffffff80d2861c at trap_pfault+0x19c
#5 0xffffffff80d27dea at trap+0x47a
#6 0xffffffff80d0db92 at calltrap+0x8
#7 0xffffffff819df8ee at fzap_cursor_retrieve+0x16e
#8 0xffffffff819e4c97 at zap_cursor_retrieve+0x1f7
#9 0xffffffff81a1fed6 at zfs_freebsd_readdir+0x426
#10 0xffffffff80e456b7 at VOP_READDIR_APV+0xa7
#11 0xffffffff809d68cc at kern_getdirentries+0x21c
#12 0xffffffff809d6688 at sys_getdirentries+0x28
#13 0xffffffff80d28da1 at amd64_syscall+0x351
#14 0xffffffff80d0de7b at Xfast_syscall+0xfb
Uptime: 1m51s

Unfortunately it's ZFS only, so I have no space to white panic dump.

I'm now trying to rebuild kernel with debugger turned on, as luckily I have 
working console at SOL...

Any preliminary hints?

-- 
Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
[ FreeBSD committer:                                 marck at FreeBSD.org ]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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