tree 0291bb7ac5bbfa44f86e3f6f9d57b708d6c34337
parent a62cbac4ce2db79c14ff299e98ee556b57467c19
author Max Reitz <mreitz@redhat.com> 1524317369 +0200
committer Max Reitz <mreitz@redhat.com> 1526393721 +0200

iotests: Add test for COR across nodes

COR across nodes (that is, you have some filter node between the
actually COR target and the node that performs the COR) cannot reliably
work together with the permission system when there is no explicit COR
node that can request the WRITE_UNCHANGED permission for its child.
This is because COR (currently) sneaks its requests by the usual
permission checks, so it can work without a WRITE* permission; but if
there is a filter node in between, that will re-issue the request, which
then passes through the usual check -- and if nobody has requested a
WRITE_UNCHANGED permission, that check will fail.

There is no real direct fix apart from hoping that there is someone who
has requested that permission; in case of just the qemu-io HMP command
(and no guest device), however, that is not the case.  The real real fix
is to implement the copy-on-read flag through an implicitly added COR
node.  Such a node can request the necessary permissions as shown in
this test.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20180421132929.21610-10-mreitz@redhat.com
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>