Libguestfs - Jan 2011 - [PATCH] Don't remove foreign kernels during conversion

Removing xen kernels during conversion is tidier, but occasionally problematic.
For example, if the kernel has dependent kmods which prevent its uninstallation,
the code to remove it reliably across multiple versions of RHEL becomes tricky.
The existing code doesn't handle this at all, and the conversion will fail
in
this case.

As it isn't strictly necessary to remove xen kernels, this change simply
stops
attempting to remove them.

Fixes RHBZ#643867
---
 lib/Sys/VirtV2V/Converter/RedHat.pm |   66 +++++------------------------------
 1 files changed, 9 insertions(+), 57 deletions(-)

diff --git a/lib/Sys/VirtV2V/Converter/RedHat.pm
b/lib/Sys/VirtV2V/Converter/RedHat.pm
index d8f9141..61e81dc 100644
--- a/lib/Sys/VirtV2V/Converter/RedHat.pm
+++ b/lib/Sys/VirtV2V/Converter/RedHat.pm
@@ -538,21 +538,11 @@ sub _configure_kernel
 {
     my ($virtio, $g, $config, $desc, $dom) = @_;
 
-    my @remove_kernels = ();
-
-    # Remove foreign hypervisor specific kernels from the list of available
-    # kernels
-    foreach my $kernel (_find_hv_kernels($desc)) {
-        # Don't actually try to remove them yet in case we remove them all.
This
-        # might make your dependency checker unhappy.
-        push(@remove_kernels, $kernel);
-    }
-
     # Pick first appropriate kernel returned by _list_kernels
     my $boot_kernel;
     foreach my $kernel (_list_kernels($g, $desc)) {
-        # Skip kernels we're going to remove
-        next if (grep(/^$kernel$/, @remove_kernels));
+        # Skip foreign kernels
+        next if _is_hv_kernel($g, $kernel);
 
         # If we're configuring virtio, check this kernel supports it
         next if ($virtio && !_supports_virtio($kernel, $g));
@@ -570,18 +560,11 @@ sub _configure_kernel
         $boot_kernel = _install_good_kernel($g, $config, $desc, $dom);
     }
 
-    # Check we have a bootable kernel. If we don't, we're probably
about to
-    # remove all kernels, which will fail unpleasantly. Fail nicely instead.
+    # Check we have a bootable kernel.
     die(user_message(__"No bootable kernels installed, and no replacement
".
                        "is available.\nUnable to continue."))
         unless(defined($boot_kernel));
 
-    # It's safe to remove kernels now
-    foreach my $kernel (@remove_kernels) {
-        # Uninstall the kernel from the guest
-        _remove_kernel($kernel, $g);
-    }
-
     return $boot_kernel;
 }
 
@@ -631,34 +614,18 @@ sub _get_os_arch
     return $arch;
 }
 
-# Return a list of foreign hypervisor specific kernels
-sub _find_hv_kernels
+# Determine if a specific kernel is hypervisor-specific
+sub _is_hv_kernel
 {
-    my $desc = shift;
-
-    my $boot = $desc->{boot};
-    return () unless(defined($boot));
-
-    my $configs = $desc->{boot}->{configs};
-    return () unless(defined($configs));
+    my ($g, $version) = @_;
 
     # Xen PV kernels can be distinguished from other kernels by their inclusion
     # of the xennet driver
-    my @kernels = ();
-    foreach my $config (@$configs) {
-        my $kernel = $config->{kernel};
-        next unless(defined($kernel));
-
-        my $modules = $kernel->{modules};
-        next unless(defined($modules));
-
-        # Look for the xennet driver in the modules list
-        if(grep(/^xennet$/, @$modules) > 0) {
-            push(@kernels, $kernel->{version});
-        }
+    foreach my $entry ($g->find("/lib/modules/$version/")) {
+        return 1 if $entry =~ /(^|\/)xennet\.k?o$/;
     }
 
-    return @kernels;
+    return 0;
 }
 
 sub _remove_application
@@ -1457,21 +1424,6 @@ sub _install_good_kernel
     return $version;
 }
 
-sub _remove_kernel
-{
-    my ($version, $g) = @_;
-
-    # Work out which rpm contains the kernel
-    my @output = $g->command_lines(['rpm', '-qf',
"/boot/vmlinuz-$version"]);
-    $g->command(['rpm', '-e', $output[0]]);
-
-    # Make augeas reload so it knows the kernel's gone
-    eval {
-        $g->aug_load();
-    };
-    augeas_error($g, $@) if ($@);
-}
-
 sub _find_new_kernel
 {
     my $g = shift;
-- 
1.7.3.5

On Thu, Jan 20, 2011 at 05:36:33PM +0000, Matthew Booth
wrote:
> Removing xen kernels during conversion is tidier, but occasionally
> problematic.  For example, if the kernel has dependent kmods which
> prevent its uninstallation, the code to remove it reliably across
> multiple versions of RHEL becomes tricky.  The existing code doesn't
> handle this at all, and the conversion will fail in this case.  As
> it isn't strictly necessary to remove xen kernels, this change
> simply stops attempting to remove them.
ACK .. a sensible change as discussed on IRC.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v