install/56227: Install fails with newfs: /dev/rdk1: open for write: Read-only file system

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

>Number:         56227
>Category:       install
>Synopsis:       Install fails with newfs: /dev/rdk1: open for write: Read-only file system
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 01 09:05:00 +0000 2021
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2021.05.22.13.43.50
>Organization:
  
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

Installing NetBSD-current/i386 in a qemu virtual machine with 32 MB
RAM (the minimum supported according to the i386 INSTALL document)
now fails with the error message

  newfs: /dev/rdk1: open for write: Read-only file system

The problem does not occur with 64 MB RAM.  I suspect the problem is
related to swap being configured differently in the two cases, because
with 32M, the kernel logs messages about configuring two dk devices:

  dk0 at wd0: "9cd2e8af-a590-4080-b51e-4325ccd1c4b7", 65535 blocks at 3080160, type: swap
  dk1 at wd0: "33bc20c6-7dfe-4d8c-9cd4-d7897b504e7b", 3080124 blocks at 34, type: ffs

whereas with 64M, there is only one:

  dk0 at wd0: "90cac3c2-6095-4bc0-9126-d7cd42ef3e9c", 3014588 blocks at 34, type: ffs

Bisection shows that the problem started with a recent commit:

  2021.05.22.13.43.50 mlelstv src/sys/dev/dkwedge/dk.c 1.103

>How-To-Repeat:

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

Run:

  anita --memory-size 32M --structured-log-file=install.slog install http://nycdn.netbsd.org/pub/NetBSD-daily/HEAD/latest/i386/

Observe that sysinst fails and drops back to the main menu.

Kill anita by typing control-c twice (or wait a long time for it to
time out).

Search the file install.slog for the string "newfs:" to find the error
message.

>Fix: