On Fri 27 Mar 2020 07:57:40 PM CET, Eric Blake wrote:
>> +/* If the image does not support QCOW_OFLAG_ZERO then discarding
>> + * clusters could expose stale data from the backing file. */
>> +if (s->qcow_version < 3 && bs->backing) {
>> +return -ENOTSUP;
>> +}
>
> Hmm.
On 3/27/20 11:48 AM, Alberto Garcia wrote:
A discard request deallocates the selected clusters so they read back
as zeroes. This is done by clearing the cluster offset field and
setting QCOW_OFLAG_ZERO in the L2 entry.
This flag is however only supported when qcow_version >= 3. In older
images
On 3/27/20 1:43 PM, Alberto Garcia wrote:
On Fri 27 Mar 2020 07:13:04 PM CET, Eric Blake wrote:
+for qcow2_compat in 0.10 1.1; do
+echo "# Create an image with compat=$qcow2_compat without a backing file"
+_make_test_img -o "compat=$qcow2_compat" 128k
+
+echo "# Fill all clusters
On Fri 27 Mar 2020 07:13:04 PM CET, Eric Blake wrote:
>> +for qcow2_compat in 0.10 1.1; do
>> +echo "# Create an image with compat=$qcow2_compat without a backing
>> file"
>> +_make_test_img -o "compat=$qcow2_compat" 128k
>> +
>> +echo "# Fill all clusters with data and then discard
On 3/27/20 11:48 AM, Alberto Garcia wrote:
A discard request deallocates the selected clusters so they read back
as zeroes. This is done by clearing the cluster offset field and
setting QCOW_OFLAG_ZERO in the L2 entry.
This flag is however only supported when qcow_version >= 3. In older
images
A discard request deallocates the selected clusters so they read back
as zeroes. This is done by clearing the cluster offset field and
setting QCOW_OFLAG_ZERO in the L2 entry.
This flag is however only supported when qcow_version >= 3. In older
images the cluster is simply deallocated, exposing
