Fetch the data to be written from the input buffer. If it is all zeroes,
we can use the write_zeroes call (possibly with the new MAY_UNMAP flag).
Otherwise, do as many write cycles as needed, writing 512k at a time.
Strictly speaking, this is still incorrect because a zero cluster should
only be written if the MAY_UNMAP flag is set. But this is a bug in qcow2
and the other formats, not in the SCSI code.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
84f94a9a82