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Re: [Libguestfs] [PATCH] Fix device name mapping for libata guests

On 12/10/10 14:08, Daniel P. Berrange wrote:
On Tue, Oct 12, 2010 at 02:05:25PM +0100, Matthew Booth wrote:
remap_block_devices was modifying the global device list while remapping device
names for libata guests (which includes RHEL 6). This caused a failure later
when the renamed devices were not present in the original XML.

Fixes RHBZ#641869
  lib/Sys/VirtV2V/GuestOS/RedHat.pm |   14 +++++++++++++-
  1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/lib/Sys/VirtV2V/GuestOS/RedHat.pm b/lib/Sys/VirtV2V/GuestOS/RedHat.pm
index a322a5d..cc95fd8 100644
--- a/lib/Sys/VirtV2V/GuestOS/RedHat.pm
+++ b/lib/Sys/VirtV2V/GuestOS/RedHat.pm
@@ -1567,7 +1567,19 @@ sub remap_block_devices

-            map { $_ = $map{$_} } @$devices;
+            # N.B. Don't use map() here because we mustn't modify the original
+            # devices list

The problem isn't that you used map(), it is that your map code block
has side effects. You should be able to avoid the side effect thus:

       my @newdevices = map { $map{$_} } @$devices;

Thanks, Dan.

As it turns out I'm going to leave the loop as is because it contains an additional sanity check which spoils the conciseness of map(). With the extra test, I think this form is cleaner. I have, however, updated the comment to not blame map :)

Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

GPG ID:  D33C3490
GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490

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