kern/56533: fs/ffs/t_miscquota:default_deny_user_big fails randomly

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         56533
>Category:       kern
>Synopsis:       fs/ffs/t_miscquota:default_deny_user_big fails randomly
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Dec 03 10:00:01 +0000 2021
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2021.09.30.03.23.48
>Organization:
  
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

On multiple i386 testbeds, the fs/ffs/t_miscquota:default_deny_user_big
test case fails in about half the runs.  For example, in this recent
run on the TNF testbed, it was the sole unexpected failure:

  http://releng.netbsd.org/b5reports/i386/2021/2021.12.03.05.28.32/test.html#failed-tcs-summary

It's failing not only under qemu, but also on real i386 hardware:

  https://www.gson.org/netbsd/bugs/build/i386-laptop/2021/2021.11.28.11.49.10/test.html#fs_ffs_t_miscquota_default_deny_user_big

Bisection indicates that the problem started with this commit (which
is strange, as there is no obvious connection between the change and
the failing test case):

  2021.09.30.03.23.48 yamaguchi src/sys/net/if.c 1.492
  2021.09.30.03.23.48 yamaguchi src/sys/net/if.h 1.294

>How-To-Repeat:

Install emulators/qemu and misc/py-anita from pkgsrc and run:

$ anita --memory-size 128M interact http://nycdn.netbsd.org/pub/NetBSD-daily/HEAD/latest/i386/
login: root
# cd /usr/tests/fs/ffs
# while atf-run t_miscquota:default_deny_user_big; do true; done

>Fix: