On Sun, Jun 28, 2020 at 2:40 AM Bryan Linton <b...@shoshoni.info> wrote:

> On 2020-06-27 19:29:31, Bob Beck <b...@obtuse.com> wrote:
> >
> > No.
> >
> > I know *exactly* what needbuf is but to attempt to diagnose what your
> > problem is we need exact details. especially:
> >
> > 1) The configuration of your system including all the details of the
> filesystems
> > you have mounted, all options used, etc.
> >
> > 2) The script you are using to generate the problem (Not a paraphrasing
> of what
> > you think the script does) What filesystems it is using.
> >
>
> Not the OP, but this problem sounds almost exactly like the bug I
> reported last year.
>
> There is a detailed list of steps I used to reproduce the bug in
> the following bug report.
>
>         https://marc.info/?l=openbsd-bugs&m=156412299418191
>
> I was even able to bisect and identify the commit which first
> caused the breakage for me.
>
>
> ---8<---
>
> CVSROOT:        /cvs
> Module name:    src
> Changes by:     b...@cvs.openbsd.org    2019/05/08 06:40:57
>
> Modified files:
>         sys/kern       : vfs_bio.c vfs_biomem.c
>
> Log message:
> Modify the buffer cache to always flip recovered DMA buffers high.
>
> This also modifies the backoff logic to only back off what is requested
> and not a "mimimum" amount. Tested by me, benno@, tedu@ anda ports build
> by naddy@.
>
> ok tedu@
>
> ---8<---
>
> However, I have since migrated away from using vnd(4)s since I was
> able to find other solutions that worked for my use cases.  So I
> may not be able to provide much additional information other than
> what is contained in the above bug report.
>
> --
> Bryan
>
> >
> >
>
>
Reproduction of BUG.


# optional
mkdir /tmpfs
mount_mfs -o rw -s 2500M swap /tmpfs # i mounted through fstab so this line
is not tested
#the bug
/bin/dd if=/dev/zero of=/tmpfs/img.dd count=0 bs=1 seek=2500000000
vnconfig vnd3 /tmpfs/img.dd
printf "a a\n\n\n\nw\nq\n" | disklabel -E vnd3
newfs vnd3a
mount /dev/vnd3a /mnt
cd /tmp && ftp https://cdn.openbsd.org/pub/OpenBSD/6.7/amd64/base67.tgz
cd /mnt
#will occur here (the mkdir was ub beedbuf state for a while ...
for v in 1 2 3 4 5 6 7 8 9; do mkdir /tmp/$v; tar xzvf /tmp/base67.tgz -C
/mnt/$v; done

Ready to test patches.



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