bin/56270: dump(8) can no longer dump a file-system

[tron%zhadum.org.uk@localhost]

>Number:         56270
>Category:       bin
>Synopsis:       dump(8) can no longer dump a file-system
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jun 22 21:05:00 +0000 2021
>Originator:     tron%zhadum.org.uk@localhost
>Release:        NetBSD 9.99.85 2021-06-22 sources
>Organization:
Matthias Scheler                                 https://zhadum.org.uk/
>Environment:
System: NetBSD lyssa.zhadum.org.uk 9.99.85 NetBSD 9.99.85 (GENERIC) #0: Tue Jun 22 10:38:17 BST 2021 tron%lyssa.zhadum.org.uk@localhost:/src/sys/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
Creating a file-system backup with dump(8) no longer works. The system
reports errors like this:

  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705847]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705846]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705845]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705844]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705843]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705842]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705841]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705840]: count=512
  DUMP: read error from /dev/rld0a: Invalid argument: [sector -4671879607123705839]: count=512

The file-system is not corrupt, at least no in a way that "fsck -f" could
detect. The same virtual machine managed to complete a backup without
problems using a 2021-06-15 NetBSD-current build.

>How-To-Repeat:
dump -u0f - / >/dev/null

>Fix:
Downgrading the source in "src/sbin/dump" to 2021-06-18 and rebuilding
"dump" fixes the problem. Based on this it is very likely that the
following commit caused the problem:

http://mail-index.netbsd.org/source-changes/2021/06/19/msg130288.html