Re: kern/54541: kernel panic using "zfs diff"

[Brad Spencer <brad%anduin.eldar.org@localhost>]

"J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost> writes:

> The following reply was made to PR kern/54541; it has been noted by GNATS.
>
> From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
> To: gnats-bugs%netbsd.org@localhost
> Cc: 
> Subject: Re: kern/54541: kernel panic using "zfs diff"
> Date: Sat, 12 Oct 2019 10:02:28 +0200
>
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>  > On 12. Oct 2019, at 01:50, Brad Spencer <brad%anduin.eldar.org@localhost> wrote:
>  <snip>
>  >=20
>  > [ 472375.2036056] panic: kernel diagnostic assertion "fdm !=3D NULL" =
>  failed: file "/usr/src/sys/kern/vfs_trans.c", line 166 mount 0x0 invalid
>  
>  Sorry for being late, looks like vn_rdwr() gets called
>  with garbage instead of a vnode.
>  
>  The attached diff could help to track it down.
>  
>  Do you have a recipe to trigger this panic?
>  
>  --
>  J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig


For me personally, it is something like this, although I don't know how
much of this matters:

sysctl -w ddb.onpanic=1
zpool create tank xbd4d  <- 1GB presented to a DOMU
zfs create tank/ds1
zfs set quota=100m tank/ds1
(fill tank/ds1 up to about 80% or so with anything, I used multiple files, but I doubt that matters)
zfs snapshot tank/ds1@sn1
(change tank/ds1.  Add or delete something, I think any change will work)
You will end up with something like this:
test3# zfs list -t all
NAME           USED  AVAIL  REFER  MOUNTPOINT
rstuff         264M  1.55G    23K  /rstuff
rstuff/var     261M   139M   261M  legacy
tank          80.8M  1.73G    23K  /tank
tank/ds1      80.2M  19.8M  80.2M  /tank/ds1
tank/ds1@sn1    18K      -  80.2M  -
zfs diff tank/ds1@sn1
panic here

I applied the included patch to a test build which is building now, but
I can't retest this for a bit.  The test DOMU that triggers this has 1GB
of memory given to it and is running a pretty recent build.



-- 
Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org