hwe-5.11 regression: zfs send core dump

[Simon Déziel]

With HWE kernel (5.11.0-25.27~20.04.1):

# zfs send -w -I data/home/sdeziel@autosnap_2021-08-05_00:00:03_daily data/home/sdeziel@syncoid_sdeziel-desktop_2021-08-07:10:14:24 > /dev/null
internal error: Invalid argument
Aborted (core dumped)
# zfs send -w -nvI data/home/sdeziel@autosnap_2021-08-05_00:00:03_daily data/home/sdeziel@syncoid_sdeziel-desktop_2021-08-07:10:14:24
send from @autosnap_2021-08-05_00:00:03_daily to data/home/sdeziel@syncoid_sdeziel-desktop_2021-08-07:10:14:24 estimated size is 274M
total estimated size is 274M

Switching back to the 5.8 kernel works:

# uname -a
Linux sdeziel-desktop 5.8.0-63-generic #71~20.04.1-Ubuntu SMP Thu Jul 15 17:46:08 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
# zfs send -w -nvI data/home/sdeziel@autosnap_2021-08-05_00:00:03_daily data/home/sdeziel@syncoid_sdeziel-desktop_2021-08-07:10:14:24
send from @autosnap_2021-08-05_00:00:03_daily to data/home/sdeziel@syncoid_sdeziel-desktop_2021-08-07:10:14:24 estimated size is 274M
total estimated size is 274M
# zfs send -w -I data/home/sdeziel@autosnap_2021-08-05_00:00:03_daily data/home/sdeziel@syncoid_sdeziel-desktop_2021-08-07:10:14:24 > /dev/null
# echo $?
0

Additional information:

$ lsb_release -rd
Description: Ubuntu 20.04.2 LTS
Release: 20.04
$ apt-cache policy linux-image-5.11.0-25-generic
linux-image-5.11.0-25-generic:
  Installed: 5.11.0-25.27~20.04.1
  Candidate: 5.11.0-25.27~20.04.1
  Version table:
 *** 5.11.0-25.27~20.04.1 500
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
        100 /var/lib/dpkg/status
$ apt-cache policy zfsutils-linux
zfsutils-linux:
  Installed: 0.8.3-1ubuntu12.12
  Candidate: 0.8.3-1ubuntu12.12
  Version table:
 *** 0.8.3-1ubuntu12.12 500
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     0.8.3-1ubuntu12.9 500
        500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
     0.8.3-1ubuntu12 500
        500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages

[Simon Déziel (sdeziel)]

I noticed there is also a problem with redirecting to /dev/null, somehow:

# uname -a
Linux sdeziel-desktop 5.11.0-27-generic #29~20.04.1-Ubuntu SMP Wed Aug 11 15:58:17 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
# zfs send -I data/simon/musique@laptop-2020-11-30 data/simon/musique@o > /dev/null
internal error: Invalid argument
Aborted (core dumped)
# dmesg -c
[ 747.837066] kernel write not supported for file /null (pid: 10174 comm: zfs)

Writing to a pipe works though:

# zfs send -I data/simon/musique@laptop-2020-11-30 data/simon/musique@o | wc -c
5660616