[Qemu-devel] [RFC V8 08/24] qcow2: Create a way to link to l2 tables when deduplicating.

["Benoît Canet" <benoit@irqsave.net>]

Signed-off-by: Benoit Canet <benoit@irqsave.net>
---
 block/qcow2-cluster.c |    6 ++++--
 block/qcow2.h         |    6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index c71470a..d6db0b9 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -696,7 +696,7 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
             old_cluster[j++] = l2_table[l2_index + i];
 
         l2_table[l2_index + i] = cpu_to_be64((cluster_offset +
-                    (i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
+                    (i << s->cluster_bits)) | m->l2_entry_flags);
      }
 
 
@@ -709,7 +709,7 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
      * If this was a COW, we need to decrease the refcount of the old cluster.
      * Also flush bs->file to get the right order for L2 and refcount update.
      */
-    if (j != 0) {
+    if (!m->overwrite && j != 0) {
         for (i = 0; i < j; i++) {
             qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1);
         }
@@ -1098,6 +1098,8 @@ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
             .offset     = nb_sectors * BDRV_SECTOR_SIZE,
             .nb_sectors = avail_sectors - nb_sectors,
         },
+        .l2_entry_flags = QCOW_OFLAG_COPIED,
+        .overwrite      = false,
     };
     qemu_co_queue_init(&(*m)->dependent_requests);
     QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight);
diff --git a/block/qcow2.h b/block/qcow2.h
index 9a9abd3..7754065 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -438,6 +438,12 @@ typedef struct QCowL2Meta
      */
     CoQueue dependent_requests;
 
+    /* contains the flags to apply to the l2 entry */
+    uint64_t l2_entry_flags;
+
+    /* set to true if we are overwriting an L2 table entry */
+    bool overwrite;
+
     /**
      * The COW Region between the start of the first allocated cluster and the
      * area the guest actually writes to.
-- 
1.7.10.4