Re: openzfs panic: VERIFY3U(offset, <, dn->dn_datablksz) failed

On 25/04/2026 10:24, Kristof Provost wrote:
> On 24 Apr 2026, at 14:18, Alexander Leidinger wrote:
>     recent current (last commit 2026-04-23-222413).
> 
>     short:
>     #3 0xffffffff805502f7 in vpanic (
>     fmt=0xffffffff82556d5d "VERIFY3U(offset, <, dn->dn_datablksz) failed
>     (%llu < %llu)\n", ap=ap@entry=0xfffffe0228f57c70)
>     at /space/system/usr_src/sys/kern/kern_shutdown.c:974
>     buf = "VERIFY3U(offset, <, dn->dn_datablksz) failed
>     (9223372036854775807 < 24576)\n", '\000' <repeats 180 times>
>     __pc = 0x0
>     __pc = 0x0
>     __pc = 0x0
>     other_cpus = {__bits = {16777213, 0 <repeats 15 times>}}
>     td = 0xfffff80741b6e780
>     bootopt = <unavailable>
>     newpanic = <optimized out>
> 
> I’m seeing the same panic (somewhat regularly, without obvious trigger), 
> so I’m fairly confident it’s not some obscure corruption in your pool.
I get it while working on RabbitMQ as well, 100% reproducible. I shared 
what I think I understand of the problem on the pull request that added 
POSIX_FADV_DONTNEED support:
https://github.com/openzfs/zfs/pull/18399

However, the patch I drafted, even though it does not cause the panic 
anymore, is incorrect as I misunderstood that code.

-- 
Jean-Sébastien Pédron
The FreeBSD Project