[Bug 270789] zpool list loads zfs.ko, even on systems that don't use zfs

From: <bugzilla-noreply_at_freebsd.org>
Date: Wed, 12 Apr 2023 14:34:20 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=270789

            Bug ID: 270789
           Summary: zpool list loads zfs.ko, even on systems that don't
                    use zfs
           Product: Base System
           Version: Unspecified
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: me@rubin55.org

I noticed that zfs.ko got loaded unexpectedly on a few small systems I
maintain, which don't run ZFS but only have UFS filesystems.

Turned out that btop executed "zpool list" unconditionally to find out if there
are any ZFS pools available. This caused zfs.ko to be loaded, which in turn
causes a "zfskern" process to spike all cpu cores at 100% for about 10 seconds.

I was discussing this with @nimaje on #freebsd on Libera and decided to file a
bug. Our thinking was that probably, zpool and/or other zfs utilities should
not auto-load zfs.ko at all.

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