block/qcow2: Implement status CB for amend

The only really time-consuming operation potentially performed by
qcow2_amend_options() is zero cluster expansion when downgrading qcow2
images from compat=1.1 to compat=0.10, so report status of that
operation and that operation only through the status CB.

For this, approximate the progress as the number of L1 entries visited
during the operation.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Benoît Canet <benoit.canet@nodalink.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Message-id: 1414404776-4919-5-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/qcow2-cluster.c

@@ -1618,10 +1618,17 @@ fail:
  * zero expansion (i.e., has been filled with zeroes and is referenced from an
  * L2 table). nb_clusters contains the total cluster count of the image file,
  * i.e., the number of bits in expanded_clusters.
+ *
+ * l1_entries and *visited_l1_entries are used to keep track of progress for
+ * status_cb(). l1_entries contains the total number of L1 entries and
+ * *visited_l1_entries counts all visited L1 entries.
  */
 static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
                                       int l1_size, uint8_t **expanded_clusters,
-                                      uint64_t *nb_clusters)
+                                      uint64_t *nb_clusters,
+                                      int64_t *visited_l1_entries,
+                                      int64_t l1_entries,
+                                      BlockDriverAmendStatusCB *status_cb)
 {
     BDRVQcowState *s = bs->opaque;
     bool is_active_l1 = (l1_table == s->l1_table);
@@ -1644,6 +1651,10 @@ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
 
         if (!l2_offset) {
             /* unallocated */
+            (*visited_l1_entries)++;
+            if (status_cb) {
+                status_cb(bs, *visited_l1_entries, l1_entries);
+            }
             continue;
         }
 
@@ -1776,6 +1787,11 @@ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
                 }
             }
         }
+
+        (*visited_l1_entries)++;
+        if (status_cb) {
+            status_cb(bs, *visited_l1_entries, l1_entries);
+        }
     }
 
     ret = 0;
@@ -1802,15 +1818,24 @@ fail:
  * allocation for pre-allocated ones). This is important for downgrading to a
  * qcow2 version which doesn't yet support metadata zero clusters.
  */
-int qcow2_expand_zero_clusters(BlockDriverState *bs)
+int qcow2_expand_zero_clusters(BlockDriverState *bs,
+                               BlockDriverAmendStatusCB *status_cb)
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t *l1_table = NULL;
     uint64_t nb_clusters;
+    int64_t l1_entries = 0, visited_l1_entries = 0;
     uint8_t *expanded_clusters;
     int ret;
     int i, j;
 
+    if (status_cb) {
+        l1_entries = s->l1_size;
+        for (i = 0; i < s->nb_snapshots; i++) {
+            l1_entries += s->snapshots[i].l1_size;
+        }
+    }
+
     nb_clusters = size_to_clusters(s, bs->file->total_sectors *
                                    BDRV_SECTOR_SIZE);
     expanded_clusters = g_try_malloc0((nb_clusters + 7) / 8);
@@ -1820,7 +1845,9 @@ int qcow2_expand_zero_clusters(BlockDriverState *bs)
     }
 
     ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size,
-                                     &expanded_clusters, &nb_clusters);
+                                     &expanded_clusters, &nb_clusters,
+                                     &visited_l1_entries, l1_entries,
+                                     status_cb);
     if (ret < 0) {
         goto fail;
     }
@@ -1854,7 +1881,9 @@ int qcow2_expand_zero_clusters(BlockDriverState *bs)
         }
 
         ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size,
-                                         &expanded_clusters, &nb_clusters);
+                                         &expanded_clusters, &nb_clusters,
+                                         &visited_l1_entries, l1_entries,
+                                         status_cb);
         if (ret < 0) {
             goto fail;
         }

block/qcow2.c

@@ -2550,7 +2550,8 @@ static int qcow2_load_vmstate(BlockDriverState *bs, uint8_t *buf,
  * Downgrades an image's version. To achieve this, any incompatible features
  * have to be removed.
  */
-static int qcow2_downgrade(BlockDriverState *bs, int target_version)
+static int qcow2_downgrade(BlockDriverState *bs, int target_version,
+                           BlockDriverAmendStatusCB *status_cb)
 {
     BDRVQcowState *s = bs->opaque;
     int current_version = s->qcow_version;
@@ -2599,7 +2600,7 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version)
     /* clearing autoclear features is trivial */
     s->autoclear_features = 0;
 
-    ret = qcow2_expand_zero_clusters(bs);
+    ret = qcow2_expand_zero_clusters(bs, status_cb);
     if (ret < 0) {
         return ret;
     }
@@ -2692,7 +2693,7 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
                 return ret;
             }
         } else {
-            ret = qcow2_downgrade(bs, new_version);
+            ret = qcow2_downgrade(bs, new_version, status_cb);
             if (ret < 0) {
                 return ret;
             }

block/qcow2.h

@@ -537,7 +537,8 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
     int nb_sectors, enum qcow2_discard_type type, bool full_discard);
 int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);
 
-int qcow2_expand_zero_clusters(BlockDriverState *bs);
+int qcow2_expand_zero_clusters(BlockDriverState *bs,
+                               BlockDriverAmendStatusCB *status_cb);
 
 /* qcow2-snapshot.c functions */
 int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);