[RFC PATCH v3 24/27] qcow2: Restrict qcow2_co_pwrite_zeroes() to full clusters only

[Alberto Garcia]

Ideally it should be possible to zero individual subclusters using
this function, but this is currently not implemented.

Signed-off-by: Alberto Garcia <address@hidden>
---
 block/qcow2.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index 242001afa2..0267722065 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3754,6 +3754,12 @@ static coroutine_fn int 
qcow2_co_pwrite_zeroes(BlockDriverState *bs,
             qemu_co_mutex_unlock(&s->lock);
             return -ENOTSUP;
         }
+        /* TODO: allow zeroing separate subclusters, we only allow
+         * zeroing full clusters at the moment. */
+        if (nr != bytes) {
+            qemu_co_mutex_unlock(&s->lock);
+            return -ENOTSUP;
+        }
         if (type != QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN &&
             type != QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC &&
             type != QCOW2_SUBCLUSTER_ZERO_PLAIN &&
-- 
2.20.1