NetBSD Problem Report #55735
From bernd@bor.bersie.loc Mon Oct 19 12:59:55 2020
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Date: Mon, 19 Oct 2020 13:41:56 +0200 (CEST)
From: bernd.sieker@posteo.net
Reply-To: bernd.sieker@posteo.net
To: gnats-bugs@NetBSD.org
Subject: union fs on top of nfs causes kernel panic
X-Send-Pr-Version: 3.95
>Number: 55735
>Category: kern
>Synopsis: union fs on top of nfs causes kernel panic
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: kern-bug-people
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Mon Oct 19 13:00:01 +0000 2020
>Last-Modified: Sun May 30 07:10:01 +0000 2021
>Originator: bernd.sieker@posteo.net
>Release: NetBSD 9.1
>Organization:
>Environment:
System: NetBSD bor.bersie.loc 9.1 NetBSD 9.1 (BOR) #8: Fri Oct 16 18:32:47 CEST 2020 bernd@bor.bersie.loc:/usr/src/sys/arch/amd64/compile/BOR amd64
Architecture: x86_64
Machine: amd64
>Description:
A custom-built 9.1 kernel, including zfs (module), union and nfs file systems occasionally panics when a union filesystem is mounted on top of an nfs-mounted filesystem.
The machine is a PowerEdge T110 server with a 4-core Intel Xeon X3430 at 2.4 GHz, with 4 GB ECC RAM.
It also uses zfs, so I cannot rule that out as a contributing factor, but crashes have only happened (4 times so far within a few days) when the union filesystem was mounted, and shows union- and nfs-related syscalls.
Here is an excerpt from fstab:
niob:/usr/source /usr/source nfs rw
/usr/source/pkgsrc /usr/pkgsrc union rw,-b
The zfs module is loaded from /etc/modules.conf along with the solaris module, and one raidz1 zpool is created on three disks.
A typical traceback from the crashdump follows:
[ 13176.105223] uvm_fault(0xffffa01f0e5faa10, 0x0, 1) -> e
[ 13176.105223] fatal page fault in supervisor mode
[ 13176.105223] trap type 6 code 0 rip 0xffffffff8055e9da cs 0x8 rflags 0x10246 cr2 0x56 ilevel 0 rsp 0xffffa300684aa670
[ 13176.105223] curlwp 0xffffa01ff342c2c0 pid 1180.1 lowest kstack 0xffffa300684a82c0
[ 13176.105223] panic: trap
[ 13176.105223] cpu1: Begin traceback...
[ 13176.105223] vpanic() at netbsd:vpanic+0x143
[ 13176.105223] snprintf() at netbsd:snprintf
[ 13176.105223] startlwp() at netbsd:startlwp
[ 13176.105223] alltraps() at netbsd:alltraps+0xbb
[ 13176.105223] nfs_request() at netbsd:nfs_request+0x18d
[ 13176.115228] nfs_getattr() at netbsd:nfs_getattr+0x16e
[ 13176.115228] VOP_GETATTR() at netbsd:VOP_GETATTR+0x53
[ 13176.115228] union_loadvnode() at netbsd:union_loadvnode+0x161
[ 13176.115228] vcache_get() at netbsd:vcache_get+0x1d6
[ 13176.115228] union_allocvp() at netbsd:union_allocvp+0x218
[ 13176.115228] union_root() at netbsd:union_root+0x52
[ 13176.115228] VFS_ROOT() at netbsd:VFS_ROOT+0x1c
[ 13176.115228] lookup_once() at netbsd:lookup_once+0x262
[ 13176.115228] namei_tryemulroot() at netbsd:namei_tryemulroot+0x32e
[ 13176.115228] namei() at netbsd:namei+0x41
[ 13176.125231] fd_nameiat.isra.2() at netbsd:fd_nameiat.isra.2+0x54
[ 13176.125231] do_sys_statat() at netbsd:do_sys_statat+0x77
[ 13176.125231] sys___stat50() at netbsd:sys___stat50+0x28
[ 13176.125231] syscall() at netbsd:syscall+0x13f
[ 13176.125231] --- syscall (number 439) ---
[ 13176.125231] 70bdb056231a:
[ 13176.125231] cpu1: End traceback...
>How-To-Repeat:
Use a union-mount on an nfs-mounted filesystem and use it. Sometimes it will panic, but the exact circumstances are not known. In some cases it happened when calling "df -h", but not always.
>Fix:
Unknown
>Audit-Trail:
From: David Holland <dholland-bugs@netbsd.org>
To: gnats-bugs@netbsd.org
Cc:
Subject: Re: kern/55735: union fs on top of nfs causes kernel panic
Date: Sun, 30 May 2021 07:09:29 +0000
On Mon, Oct 19, 2020 at 01:00:01PM +0000, bernd.sieker@posteo.net wrote:
> A custom-built 9.1 kernel, including zfs (module), union and nfs
> file systems occasionally panics when a union filesystem is mounted
> on top of an nfs-mounted filesystem.
so... unfortunately panics from onionfs are not exactly unexpected,
though this one seems a bit odd.
> [ 13176.105223] alltraps() at netbsd:alltraps+0xbb
> [ 13176.105223] nfs_request() at netbsd:nfs_request+0x18d
Do you have debug info? If you can figure out which line of
nfs_request() that is, it would be helpful, as nfs_request() is about
450 lines of fairly messy code.
--
David A. Holland
dholland@netbsd.org
(Contact us)
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