[Qemu-devel] [RFC V5 21/36] qcow2: Remove hash when cluster is deleted.

[Benoît Canet]

---
 block/qcow2-dedup.c    |   26 ++++++++++++++++++++++++++
 block/qcow2-refcount.c |    3 +++
 block/qcow2.h          |    2 ++
 3 files changed, 31 insertions(+)

diff --git a/block/qcow2-dedup.c b/block/qcow2-dedup.c
index 9eba773..8b51dda 100644
--- a/block/qcow2-dedup.c
+++ b/block/qcow2-dedup.c
@@ -942,6 +942,32 @@ int qcow2_dedup_store_new_hashes(BlockDriverState *bs,
     return ret;
 }
 
+/* Clean the last reference to a given cluster when it's refcount is zero
+ *
+ * @cluster_index: the index of the physical cluster
+ */
+void qcow2_dedup_refcount_zero_reached(BlockDriverState *bs,
+                                      uint64_t cluster_index)
+{
+    BDRVQcowState *s = bs->opaque;
+    QCowHash null_hash;
+    uint64_t logical_sect = 0;
+    uint64_t physical_sect = cluster_index * s->cluster_sectors;
+
+    /* prepare null hash */
+    memset(&null_hash, 0, sizeof(null_hash));
+
+    /* clear from disk */
+    qcow2_dedup_read_write_hash(bs,
+                                &null_hash,
+                                &logical_sect,
+                                physical_sect,
+                                true);
+
+    /* remove from ram if present so we won't dedup with it anymore */
+    qcow2_remove_hash_node_by_sector(bs, physical_sect);
+}
+
 /* Force to use a new physical cluster and QCowHashNode when the refcount pass
  * 2^16/2.
  *
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index ac396c4..6a6719f 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -492,6 +492,9 @@ int QEMU_WARN_UNUSED_RESULT 
update_refcount(BlockDriverState *bs,
         if (s->has_dedup && deduplication && refcount >= 0xFFFF/2) {
             qcow2_dedup_refcount_half_max_reached(bs, cluster_index);
         }
+        if (s->has_dedup && refcount == 0) {
+            qcow2_dedup_refcount_zero_reached(bs, cluster_index);
+        }
         if (refcount == 0 && cluster_index < s->free_cluster_index) {
             s->free_cluster_index = cluster_index;
         }
diff --git a/block/qcow2.h b/block/qcow2.h
index ba10ed0..842c321 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -501,6 +501,8 @@ int qcow2_dedup_store_new_hashes(BlockDriverState *bs,
                                  int count,
                                  uint64_t logical_sect,
                                  uint64_t physical_sect);
+void qcow2_dedup_refcount_zero_reached(BlockDriverState *bs,
+                                       uint64_t cluster_index);
 void qcow2_dedup_refcount_half_max_reached(BlockDriverState *bs,
                                            uint64_t cluster_index);
 
-- 
1.7.10.4