[Qemu-devel] [RFC PATCH v2 13/23] qcow2: handle_copied(): Implement non-zero host_offset

[Kevin Wolf]

Look only for clusters that start at a given physical offset.

Signed-off-by: Kevin Wolf <address@hidden>
---
 block/qcow2-cluster.c |   26 ++++++++++++++++++--------
 1 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 5ce2c88..90fe36c 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -827,8 +827,6 @@ static int handle_dependencies(BlockDriverState *bs, 
uint64_t guest_offset,
  *          the length of the area that can be written to.
  *
  *  -errno: in error cases
- *
- * TODO Make non-zero host_offset behave like describe above
  */
 static int handle_copied(BlockDriverState *bs, uint64_t guest_offset,
     uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m)
@@ -843,7 +841,6 @@ static int handle_copied(BlockDriverState *bs, uint64_t 
guest_offset,
 
     trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, 
*host_offset,
                               *bytes);
-    assert(*host_offset == 0);
 
     /*
      * Calculate the number of clusters to look for. We stop at L2 table
@@ -867,6 +864,15 @@ static int handle_copied(BlockDriverState *bs, uint64_t 
guest_offset,
     if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL
         && (cluster_offset & QCOW_OFLAG_COPIED))
     {
+        /* If a specific host_offset is required, check it */
+        if (*host_offset != 0
+            && (cluster_offset & L2E_OFFSET_MASK) != *host_offset)
+        {
+            *bytes = 0;
+            ret = 0;
+            goto out;
+        }
+
         /* We keep all QCOW_OFLAG_COPIED clusters */
         keep_clusters =
             count_contiguous_clusters(nb_clusters, s->cluster_size,
@@ -880,19 +886,22 @@ static int handle_copied(BlockDriverState *bs, uint64_t 
guest_offset,
 
         ret = 1;
     } else {
-        cluster_offset = 0;
         ret = 0;
     }
 
-    cluster_offset &= L2E_OFFSET_MASK;
-    *host_offset = cluster_offset;
-
     /* Cleanup */
+out:
     pret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
     if (pret < 0) {
         return pret;
     }
 
+    /* Only return a host offset if we actually made progress. Otherwise we
+     * would make requirements for handle_alloc() that it can't fulfill */
+    if (ret) {
+        *host_offset = cluster_offset & L2E_OFFSET_MASK;
+    }
+
     return ret;
 }
 
@@ -1162,7 +1171,6 @@ again:
 
     /*
      * 2. Count contiguous COPIED clusters.
-     *    TODO: Consider cluster_offset if set in step 1c.
      */
     ret = handle_copied(bs, offset, &cluster_offset, &cur_bytes, m);
     if (ret < 0) {
@@ -1175,6 +1183,8 @@ again:
         if (!*host_offset) {
             *host_offset = cluster_offset;
         }
+    } else if (cur_bytes == 0) {
+        goto done;
     } else {
         keep_clusters = 0;
     }
-- 
1.7.6.5