qcow2: Introduce Qcow2COWRegion

This makes it easier to address the areas for which a COW must be
performed. As a nice side effect, the COW code in
qcow2_alloc_cluster_link_l2 becomes really trivial.

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

1 files changed, 23 insertions, 6 deletions

diff --git a/block/qcow2.h b/block/qcow2.h
index 2a406a7e83..1106b33206 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -196,6 +196,17 @@ typedef struct QCowCreateState {
 
 struct QCowAIOCB;
 
+typedef struct Qcow2COWRegion {
+    /**
+     * Offset of the COW region in bytes from the start of the first cluster
+     * touched by the request.
+     */
+    uint64_t    offset;
+
+    /** Number of sectors to copy */
+    int         nb_sectors;
+} Qcow2COWRegion;
+
 /* XXX This could be private for qcow2-cluster.c */
 typedef struct QCowL2Meta
 {
@@ -209,12 +220,6 @@ typedef struct QCowL2Meta
     uint64_t alloc_offset;
 
     /**
-     * Number of sectors between the start of the first allocated cluster and
-     * the area that the guest actually writes to.
-     */
-    int n_start;
-
-    /**
      * Number of sectors from the start of the first allocated cluster to
      * the end of the (possibly shortened) request
      */
@@ -229,6 +234,18 @@ typedef struct QCowL2Meta
      */
     CoQueue dependent_requests;
 
+    /**
+     * The COW Region between the start of the first allocated cluster and the
+     * area the guest actually writes to.
+     */
+    Qcow2COWRegion cow_start;
+
+    /**
+     * The COW Region between the area the guest actually writes to and the
+     * end of the last allocated cluster.
+     */
+    Qcow2COWRegion cow_end;
+
     QLIST_ENTRY(QCowL2Meta) next_in_flight;
 } QCowL2Meta;