bin/55834: dump(8) stops reporting progress after 2 TB of data

[bernd.sieker%posteo.net@localhost]

>Number:         55834
>Category:       bin
>Synopsis:       dump(8) stops reporting progress after 2 TB of data
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Dec 01 07:30:00 +0000 2020
>Originator:     Bernd Sieker
>Release:        NetBSD 9.1_STABLE
>Organization:
>Environment:
NetBSD niob.bersie.loc 9.1_STABLE NetBSD 9.1_STABLE (NIOB) #37: Mon Nov 23 12:14:35 CET 2020  bernd%niob.bersie.loc@localhost:/usr/source/netbsd-9/src/sys/arch/amd64/compile/NIOB amd64

>Description:
When dumping a large file system, the dump program stops reporting progress when more than 2 TB of data have been dumped. It continues the dump process, the resulting file has a size of just under 3 TB:

$ ls -lh
-rw-r--r--  1 bernd  users  2.9T Nov 28 23:48 niob-home-L0-2020-11-27.dmp

After finishing, dump also reports a credible amount of (10k) blocks in the dump. The last lines of the dump output were as follows:

  DUMP: 67.60% done, finished in 11:42
  DUMP: 67.86% done, finished in 11:36
  DUMP: 68.13% done, finished in 11:30
  DUMP: 68.39% done, finished in 11:24
  DUMP: 68.65% done, finished in 11:18
  DUMP: 68.92% done, finished in 11:12
  DUMP: 69.18% done, finished in 11:05
  DUMP: 3096903227 tape blocks
  DUMP: Volume 1 completed at: Sat Nov 28 23:48:42 2020
  DUMP: Volume 1 took 35:24:00
  DUMP: Volume 1 transfer rate: 24300 KB/s
  DUMP: Date of this level 0 dump: Fri Nov 27 12:22:31 2020
  DUMP: Date this dump completed:  Sat Nov 28 23:48:42 2020
  DUMP: Average transfer rate: 24300 KB/s
  DUMP: DUMP IS DONE


Note that progress reports were made regularly until 69.18%, which corresponds to 2 Terabytes of data having been dumped. Reports stop, but dumping continues to the end, and the final report seems accurate.

Spot tests and hash comparisons indicate that the dump itself is also correct and complete.

>How-To-Repeat:
Use dump(8) to dump a filesystem on which more than 2 TB of data would be backed up, observe the status reports on the controlling terminal. See that reporting stops after 2 TB of data have been dumped, although dumping continues.
>Fix:
Unknown.