tree a4601e141bf87c772980c1aef6c0fd462dc3fe87
parent 18fec301cd2a38f72a5eeba2656a0c5b4fa69fb7
author Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> 1346159067 +0100
committer Kevin Wolf <kwolf@redhat.com> 1346246615 +0200

qed: refuse unaligned zero writes with a backing file

Zero writes have cluster granularity in QED.  Therefore they can only be
used to zero entire clusters.

If the zero write request leaves sectors untouched, zeroing the entire
cluster would obscure the backing file.  Instead return -ENOTSUP, which
is handled by block.c:bdrv_co_do_write_zeroes() and falls back to a
regular write.

The qemu-iotests 034 test cases covers this scenario.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>