Trap 12 in vm_page_alloc_after()

[Garrett Wollman]

Has anyone seen this before?  It's on a busy NFS server, but hasn't
been observed on any of our other NFS servers.

------------------------------------------------------------------------
Fatal trap 12: page fault while in kernel mode
cpuid = 35; apic id = 35
fault virtual address   = 0x5a
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff809a903d
stack pointer           = 0x28:0xfffffe17eb8d0710
frame pointer           = 0x28:0xfffffe17eb8d0750
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 878 (nfsd: service)
trap number             = 12
panic: page fault
cpuid = 35
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe17eb8d03c0
vpanic() at vpanic+0x177/frame 0xfffffe17eb8d0420
panic() at panic+0x43/frame 0xfffffe17eb8d0480
trap_fatal() at trap_fatal+0x35f/frame 0xfffffe17eb8d04d0
trap_pfault() at trap_pfault+0x49/frame 0xfffffe17eb8d0530
trap() at trap+0x2c7/frame 0xfffffe17eb8d0640
calltrap() at calltrap+0x8/frame 0xfffffe17eb8d0640
--- trap 0xc, rip = 0xffffffff809a903d, rsp = 0xfffffe17eb8d0710, rbp = 0xfffffe17eb8d0750 ---
vm_page_alloc_after() at vm_page_alloc_after+0x15d/frame 0xfffffe17eb8d0750
kmem_back() at kmem_back+0xf2/frame 0xfffffe17eb8d07c0
kmem_malloc() at kmem_malloc+0x60/frame 0xfffffe17eb8d07f0
keg_alloc_slab() at keg_alloc_slab+0xe2/frame 0xfffffe17eb8d0860
keg_fetch_slab() at keg_fetch_slab+0x14e/frame 0xfffffe17eb8d08b0
zone_fetch_slab() at zone_fetch_slab+0x64/frame 0xfffffe17eb8d08e0
zone_import() at zone_import+0x3f/frame 0xfffffe17eb8d0930
uma_zalloc_arg() at uma_zalloc_arg+0x3d9/frame 0xfffffe17eb8d09a0
zil_alloc_lwb() at zil_alloc_lwb+0x9c/frame 0xfffffe17eb8d09e0
zil_lwb_write_issue() at zil_lwb_write_issue+0x2f8/frame 0xfffffe17eb8d0a40
zil_commit_impl() at zil_commit_impl+0x95f/frame 0xfffffe17eb8d0b80
zfs_freebsd_fsync() at zfs_freebsd_fsync+0xa7/frame 0xfffffe17eb8d0bb0
VOP_FSYNC_APV() at VOP_FSYNC_APV+0x82/frame 0xfffffe17eb8d0be0
nfsvno_fsync() at nfsvno_fsync+0xe0/frame 0xfffffe17eb8d0c50
nfsrvd_commit() at nfsrvd_commit+0xe8/frame 0xfffffe17eb8d0e20
nfsrvd_dorpc() at nfsrvd_dorpc+0x621/frame 0xfffffe17eb8d0ff0
nfssvc_program() at nfssvc_program+0x557/frame 0xfffffe17eb8d11a0
svc_run_internal() at svc_run_internal+0xe09/frame 0xfffffe17eb8d12e0
svc_thread_start() at svc_thread_start+0xb/frame 0xfffffe17eb8d12f0
fork_exit() at fork_exit+0x83/frame 0xfffffe17eb8d1330
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe17eb8d1330
--- trap 0xc, rip = 0x80087101a, rsp = 0x7fffffffe688, rbp = 0x7fffffffe930 ---
------------------------------------------------------------------------

At this point the system was frozen: it did not attempt to reboot
automatically and was not in the debugger.  I had to do a remote reset
via the BMC.  The kernel is 11.2 r336644 (so no errata applied), but
none of the SAs and ENs release so far look like they touch this
region of code.

-GAWollman