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Re: panic: biodone2 already



For what it is worth, and in this case it might not be much, I did a similar
test on my test amd64 DomU last night.

Running dump and /etc/daily in parallel did nothing, but running lots of
them in parallel eventually did cause a crash.

But I saw a different crash -- rather than a biodone2, I got a KASSERT
from one I added as part of attempting to diagnose the babylon5
"install failures" - that is, if my test kernel ever gets an I/O error,
the KASSERT (which is just KASSERT(0)) causes a crash.   This
was intended for generic kernels that run in qemu - but I use the
same sources for my generic testing, and simply left that there.
My DomU test system *never* gets an I/O error, so it simply did
not matter (its filesystem is on a raid on the Dom0, and neither the
Dom0 nor the raid report anything even smelling like I/O errors,
what's more, the Dom0 is more likely to crash than ever allow a
real I/O error through to the DomU).

This is the I/O error that occurred...

[ 485570.8105971] xbd0a: error writing fsbn 49691936 of 49691936-49691951 (xbd0 bn 49691936; cn 24263 tn 0 sn 1312)panic: kernel diagnostic assertion "0" failed: file "/readonly/release/testing/src/sys/kern/subr_disk.c", line 163 


What's kind of interesting about that, is that the DomU filesystem is ...

format  FFSv1
endian  little-endian
magic   11954           time    Wed Aug  8 03:57:00 2018
superblock location     8192    id      [ 57248bd0 6db5a772 ]
cylgrp  dynamic inodes  4.4BSD  sblock  FFSv2   fslevel 4
nbfree  4037762 ndir    2334    nifree  2009341 nffree  3116
ncg     624     size    33554432        blocks  33289830

(no idea how I managed to make it FFSv1, but that doesn't matter).

What is interesting is "blocks  33289830" when compared with the
I/O error  "error writing fsbn 49691936" which is 16402106 blocks
beyond the end of the filesystem

This suggests to me that something is getting totally scrambled in
the buf headers when things get busy.

kre



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