qcow2: Prepare qcow2_update_snapshot_refcount() for adding L2 slice support

Adding support for L2 slices to qcow2_update_snapshot_refcount() needs
(among other things) an extra loop that iterates over all slices of
each L2 table.

Putting all changes in one patch would make it hard to read because
all semantic changes would be mixed with pure indentation changes.

To make things easier this patch simply creates a new block and
changes the indentation of all lines of code inside it. Thus, all
modifications in this patch are cosmetic. There are no semantic
changes and no variables are renamed yet. The next patch will take
care of that.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 8ffaa5e55bd51121f80e498f4045b64902a94293.1517840877.git.berto@igalia.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

block/qcow2-refcount.c

@@ -1236,90 +1236,96 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
                 goto fail;
             }
 
-            ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
-                (void**) &l2_table);
-            if (ret < 0) {
-                goto fail;
-            }
+            {
+                ret = qcow2_cache_get(bs, s->l2_table_cache,
+                                      l2_offset,
+                                      (void **) &l2_table);
+                if (ret < 0) {
+                    goto fail;
+                }
 
-            for (j = 0; j < s->l2_size; j++) {
-                uint64_t cluster_index;
-                uint64_t offset;
-
-                entry = be64_to_cpu(l2_table[j]);
-                old_entry = entry;
-                entry &= ~QCOW_OFLAG_COPIED;
-                offset = entry & L2E_OFFSET_MASK;
-
-                switch (qcow2_get_cluster_type(entry)) {
-                case QCOW2_CLUSTER_COMPRESSED:
-                    nb_csectors = ((entry >> s->csize_shift) &
-                                   s->csize_mask) + 1;
-                    if (addend != 0) {
-                        ret = update_refcount(bs,
-                                (entry & s->cluster_offset_mask) & ~511,
+                for (j = 0; j < s->l2_size; j++) {
+                    uint64_t cluster_index;
+                    uint64_t offset;
+
+                    entry = be64_to_cpu(l2_table[j]);
+                    old_entry = entry;
+                    entry &= ~QCOW_OFLAG_COPIED;
+                    offset = entry & L2E_OFFSET_MASK;
+
+                    switch (qcow2_get_cluster_type(entry)) {
+                    case QCOW2_CLUSTER_COMPRESSED:
+                        nb_csectors = ((entry >> s->csize_shift) &
+                                       s->csize_mask) + 1;
+                        if (addend != 0) {
+                            ret = update_refcount(
+                                bs, (entry & s->cluster_offset_mask) & ~511,
                                 nb_csectors * 512, abs(addend), addend < 0,
                                 QCOW2_DISCARD_SNAPSHOT);
-                        if (ret < 0) {
+                            if (ret < 0) {
+                                goto fail;
+                            }
+                        }
+                        /* compressed clusters are never modified */
+                        refcount = 2;
+                        break;
+
+                    case QCOW2_CLUSTER_NORMAL:
+                    case QCOW2_CLUSTER_ZERO_ALLOC:
+                        if (offset_into_cluster(s, offset)) {
+                            qcow2_signal_corruption(
+                                bs, true, -1, -1, "Cluster "
+                                "allocation offset %#" PRIx64
+                                " unaligned (L2 offset: %#"
+                                PRIx64 ", L2 index: %#x)",
+                                offset, l2_offset, j);
+                            ret = -EIO;
                             goto fail;
                         }
-                    }
-                    /* compressed clusters are never modified */
-                    refcount = 2;
-                    break;
-
-                case QCOW2_CLUSTER_NORMAL:
-                case QCOW2_CLUSTER_ZERO_ALLOC:
-                    if (offset_into_cluster(s, offset)) {
-                        qcow2_signal_corruption(bs, true, -1, -1, "Cluster "
-                                                "allocation offset %#" PRIx64
-                                                " unaligned (L2 offset: %#"
-                                                PRIx64 ", L2 index: %#x)",
-                                                offset, l2_offset, j);
-                        ret = -EIO;
-                        goto fail;
-                    }
 
-                    cluster_index = offset >> s->cluster_bits;
-                    assert(cluster_index);
-                    if (addend != 0) {
-                        ret = qcow2_update_cluster_refcount(bs,
-                                    cluster_index, abs(addend), addend < 0,
-                                    QCOW2_DISCARD_SNAPSHOT);
+                        cluster_index = offset >> s->cluster_bits;
+                        assert(cluster_index);
+                        if (addend != 0) {
+                            ret = qcow2_update_cluster_refcount(
+                                bs, cluster_index, abs(addend), addend < 0,
+                                QCOW2_DISCARD_SNAPSHOT);
+                            if (ret < 0) {
+                                goto fail;
+                            }
+                        }
+
+                        ret = qcow2_get_refcount(bs, cluster_index, &refcount);
                         if (ret < 0) {
                             goto fail;
                         }
-                    }
+                        break;
 
-                    ret = qcow2_get_refcount(bs, cluster_index, &refcount);
-                    if (ret < 0) {
-                        goto fail;
-                    }
-                    break;
-
-                case QCOW2_CLUSTER_ZERO_PLAIN:
-                case QCOW2_CLUSTER_UNALLOCATED:
-                    refcount = 0;
-                    break;
+                    case QCOW2_CLUSTER_ZERO_PLAIN:
+                    case QCOW2_CLUSTER_UNALLOCATED:
+                        refcount = 0;
+                        break;
 
-                default:
-                    abort();
-                }
+                    default:
+                        abort();
+                    }
 
-                if (refcount == 1) {
-                    entry |= QCOW_OFLAG_COPIED;
-                }
-                if (entry != old_entry) {
-                    if (addend > 0) {
-                        qcow2_cache_set_dependency(bs, s->l2_table_cache,
-                            s->refcount_block_cache);
+                    if (refcount == 1) {
+                        entry |= QCOW_OFLAG_COPIED;
+                    }
+                    if (entry != old_entry) {
+                        if (addend > 0) {
+                            qcow2_cache_set_dependency(bs, s->l2_table_cache,
+                                                       s->refcount_block_cache);
+                        }
+                        l2_table[j] = cpu_to_be64(entry);
+                        qcow2_cache_entry_mark_dirty(s->l2_table_cache,
+                                                     l2_table);
                     }
-                    l2_table[j] = cpu_to_be64(entry);
-                    qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
                 }
-            }
 
-            qcow2_cache_put(s->l2_table_cache, (void **) &l2_table);
+                qcow2_cache_put(s->l2_table_cache, (void **) &l2_table);
+
+            }
 
             if (addend != 0) {
                 ret = qcow2_update_cluster_refcount(bs, l2_offset >>