qcow2: Allow requests with multiple l2metas

Instead of expecting a single l2meta, have a list of them. This allows
to still have a single I/O request for the guest data, even though
multiple l2meta may be needed in order to describe both a COW overwrite
and a new cluster allocation (typical sequential write case).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/block/qcow2.h b/block/qcow2.h
index 32806bd035..bf8db2abd3 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -250,6 +250,9 @@ typedef struct QCowL2Meta
      */
     Qcow2COWRegion cow_end;
 
+    /** Pointer to next L2Meta of the same write request */
+    struct QCowL2Meta *next;
+
     QLIST_ENTRY(QCowL2Meta) next_in_flight;
 } QCowL2Meta;