Fix dkms installation of deb packages created with Alien.

Alien does not honour the %posttrans hook.
So move the dkms uninstall/install scripts to the
 %pre/%post hooks in case of package install/upgrade.
In case of package removal, handle that in %preun.
Add removal of all old dkms modules.
Add checking for broken 'dkms status'. Handle that as
good as possible and warn the user about it.
Also add more verbose messages about what we are doing.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Mart Frauenlob <AllKind@fastest.cc>
Closes openzfs#15415

rpm/generic/zfs-dkms.spec.in

@@ -24,6 +24,7 @@ BuildRoot:      %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
 BuildArch:      noarch
 
 Requires:       dkms >= 2.2.0.3
+Requires(pre):  dkms >= 2.2.0.3
 Requires(post): dkms >= 2.2.0.3
 Requires(preun): dkms >= 2.2.0.3
 Requires:       gcc, make, perl, diffutils
@@ -68,9 +69,92 @@ fi
 %defattr(-,root,root)
 /usr/src/%{module}-%{version}
 
+%pre
+echo "Running pre installation script: $0. Parameters: $*"
+# We don't want any other versions lingering around in dkms.
+# Tests with 'dnf' showed that in case of reinstall, or upgrade
+#  the preun scriptlet removed the version we are trying to install.
+# Because of this, find all zfs dkms sources in /var/lib/dkms and
+#  remove them, if we find a matching version in dkms.
+
+dkms_root=/var/lib/dkms
+if [ -d ${dkms_root}/%{module} ]; then
+    cd ${dkms_root}/%{module}
+    for x in [[:digit:]]*; do
+        [ -d "$x" ] || continue
+        otherver="$x"
+        opath="${dkms_root}/%{module}/${otherver}"
+        if [ "$otherver" != %{version} ]; then
+            # This is a workaround for a broken 'dkms status', we caused in a previous version.
+            # One day it might be not needed anymore, but it does not hurt to keep it.
+            if dkms status -m %{module} -v "$otherver" 2>&1 | grep "${opath}/source/dkms.conf does not exist"
+            then
+                echo "ERROR: dkms status is broken!" >&2
+                if [ -L "${opath}/source" -a ! -d "${opath}/source" ]
+                then
+                    echo "Trying to fix it by removing the symlink: ${opath}/source" >&2
+                    echo "You should manually remove ${opath}" >&2
+                    rm -f "${opath}/source" || echo "Removal failed!" >&2
+                fi
+            fi
+            if [ `dkms status -m %{module} -v "$otherver" | grep -c %{module}` -gt 0 ]; then
+                echo "Removing old %{module} dkms modules version $otherver from all kernels."
+                dkms remove -m %{module} -v "$otherver" --all ||:
+            fi
+        fi
+    done
+fi
+
+# Uninstall this version of zfs dkms modules before installation of the package.
+if [ `dkms status -m %{module} -v %{version} | grep -c %{module}` -gt 0 ]; then
+    echo "Removing %{module} dkms modules version %{version} from all kernels."
+    dkms remove -m %{module} -v %{version} --all ||:
+fi
+
+%post
+echo "Running post installation script: $0. Parameters: $*"
+# Add the module to dkms, as reccommended in the dkms man page.
+# This is generally rpm specfic.
+# But this also may help, if we have a broken 'dkms status'.
+# Because, if the sources are available and only the symlink pointing
+#  to them is missing, this will resolve the situation
+echo "Adding %{module} dkms modules version %{version} to dkms."
+dkms add -m %{module} -v %{version} %{!?not_rpm:--rpm_safe_upgrade} ||:
+
+# After installing the package, dkms install this zfs version for the current kernel.
+# Force the overwriting of old modules to avoid diff warnings in dkms status.
+# Or in case of a downgrade to overwrite newer versions.
+# Or if some other backed up versions have been restored before.
+echo "Installing %{module} dkms modules version %{version} for the current kernel."
+dkms install --force -m %{module} -v %{version} ||:
+
 %preun
-dkms remove -m %{module} -v %{version} --all
+dkms_root="/var/lib/dkms/%{module}/%{version}"
+echo "Running pre uninstall script: $0. Parameters: $*"
+# In case of upgrade we do nothing. See above comment in pre hook.
+if [ "$1" = "1" -o "$1" = "upgrade" ] ; then
+    echo "This is an upgrade. Skipping pre uninstall action."
+    exit 0
+fi
+
+# Check if we uninstall the package. In that case remove the dkms modules.
+# '0' is the value for the first parameter for rpm packages.
+# 'remove' or 'purge' are the possible names for deb packages.
+if [ "$1" = "0" -o "$1" = "remove" -o "$1" = "purge" ] ; then
+    if [ `dkms status -m %{module} -v %{version} | grep -c %{module}` -gt 0 ]; then
+        echo "Removing %{module} dkms modules version %{version} from all kernels."
+        dkms remove -m %{module} -v %{version} --all %{!?not_rpm:--rpm_safe_upgrade} && exit 0
+    fi
+    # If removing the modules failed, it might be because of the broken 'dkms status'.
+    if dkms status -m %{module} -v %{version} 2>&1 | grep "${dkms_root}/source/dkms.conf does not exist"
+    then
+        echo "ERROR: dkms status is broken!" >&2
+        echo "You should manually remove ${dkms_root}" >&2
+        echo "WARNING: installed modules in /lib/modules/`uname -r`/extra could not be removed automatically!" >&2
+    fi
+else
+    echo "Script parameter $1 did not match any removal condition."
+fi
 
-%posttrans
-/usr/lib/dkms/common.postinst %{module} %{version}
+exit 0