[09/22] qcow2-dirty-bitmap: add qcow2_bitmap_load()

diff --git a/block/qcow2-dirty-bitmap.c b/block/qcow2-dirty-bitmap.c
index e57058c..c9f7ef1 100644
--- a/block/qcow2-dirty-bitmap.c
+++ b/block/qcow2-dirty-bitmap.c
@@ -107,6 +107,13 @@  static int check_constraints(QCow2BitmapHeader *h, int cluster_size,
     return fail ? -EINVAL : 0;
 }
 
+static QCow2BitmapHeader *bitmap_header(BDRVQcow2State *s,
+                                        QCow2Bitmap *bitmap)
+{
+    return (QCow2BitmapHeader *)
+           (s->bitmap_directory + bitmap->offset);
+}
+
 static int directory_read(BlockDriverState *bs, Error **errp)
 {
     int ret;
@@ -210,3 +217,106 @@  fail:
 
     return ret;
 }
+
+static QCow2Bitmap *find_bitmap_by_name(BlockDriverState *bs, const char *name)
+{
+    BDRVQcow2State *s = bs->opaque;
+    QCow2Bitmap *bm, *end = s->bitmaps + s->nb_bitmaps;
+
+    for (bm = s->bitmaps; bm < end; ++bm) {
+        if (strcmp(bm->name, name) == 0) {
+            return bm;
+        }
+    }
+
+    return NULL;
+}
+
+/* load_bitmap_data()
+ * load dirty bitmap from bitmap table
+ * Bitmap table entries are assumed to be in big endian format */
+static int load_bitmap_data(BlockDriverState *bs, const uint64_t *bitmap_table,
+                            uint32_t bitmap_table_size, BdrvDirtyBitmap *bitmap)
+{
+    int ret = 0;
+    BDRVQcow2State *s = bs->opaque;
+    uint32_t i;
+    uint64_t *tab = g_memdup(bitmap_table,
+                             bitmap_table_size * sizeof(uint64_t));
+
+    for (i = 0; i < bitmap_table_size; ++i) {
+        be64_to_cpus(tab + i);
+    }
+
+    ret = bdrv_dirty_bitmap_load(bitmap, bs->file->bs, tab, bitmap_table_size,
+                                 s->cluster_size);
+
+    g_free(tab);
+
+    return ret;
+}
+
+static BdrvDirtyBitmap *load_bitmap(BlockDriverState *bs, QCow2Bitmap *bm,
+                                    Error **errp)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int ret;
+    QCow2BitmapHeader *bmh;
+    uint64_t *bitmap_table = NULL;
+    uint32_t granularity;
+    BdrvDirtyBitmap *bitmap = NULL;
+
+    bmh = bitmap_header(s, bm);
+
+    bitmap_table = g_try_malloc(bmh->bitmap_table_size * sizeof(uint64_t));
+    if (bitmap_table == NULL) {
+        error_setg_errno(errp, -ENOMEM,
+                         "Could not allocate bitmap table");
+        return NULL;
+    }
+
+    ret = bdrv_pread(bs->file->bs, bmh->bitmap_table_offset,
+                     bitmap_table,
+                     bmh->bitmap_table_size * sizeof(uint64_t));
+    if (ret < 0) {
+        error_setg_errno(errp, -ret,
+                         "Could not read bitmap_table table from image");
+        goto fail;
+    }
+
+    granularity = 1U << bmh->granularity_bits;
+    bitmap = bdrv_create_dirty_bitmap(bs, granularity, bm->name, errp);
+    if (bitmap == NULL) {
+        goto fail;
+    }
+
+    ret = load_bitmap_data(bs, bitmap_table, bmh->bitmap_table_size, bitmap);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not read bitmap from image");
+        goto fail;
+    }
+
+    g_free(bitmap_table);
+    return bitmap;
+
+fail:
+    g_free(bitmap_table);
+    bdrv_release_dirty_bitmap(bs, bitmap);
+
+    return NULL;
+}
+
+BdrvDirtyBitmap *qcow2_bitmap_load(BlockDriverState *bs, const char *name,
+                                   Error **errp)
+{
+    QCow2Bitmap *bm;
+
+    bm = find_bitmap_by_name(bs, name);
+    if (bm == NULL) {
+        error_setg(errp, "Could not find bitmap '%s' in the node '%s'", name,
+                   bdrv_get_device_or_node_name(bs));
+        return NULL;
+    }
+
+    return load_bitmap(bs, bm, errp);
+}
diff --git a/block/qcow2.c b/block/qcow2.c
index 1ce6264..5f54528 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3352,6 +3352,8 @@  BlockDriver bdrv_qcow2 = {
     .bdrv_get_info          = qcow2_get_info,
     .bdrv_get_specific_info = qcow2_get_specific_info,
 
+    .bdrv_dirty_bitmap_load = qcow2_bitmap_load,
+
     .bdrv_save_vmstate    = qcow2_save_vmstate,
     .bdrv_load_vmstate    = qcow2_load_vmstate,
 
diff --git a/block/qcow2.h b/block/qcow2.h
index 48fb2a5..cc4c776 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -620,6 +620,9 @@  int qcow2_read_snapshots(BlockDriverState *bs);
 void qcow2_free_bitmaps(BlockDriverState *bs);
 int qcow2_read_bitmaps(BlockDriverState *bs, Error **errp);
 
+BdrvDirtyBitmap *qcow2_bitmap_load(BlockDriverState *bs, const char *name,
+                                   Error **errp);
+
 /* qcow2-cache.c functions */
 Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables);
 int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index dda5ba0..d0e3db8 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -215,6 +215,10 @@  struct BlockDriver {
     int (*bdrv_get_info)(BlockDriverState *bs, BlockDriverInfo *bdi);
     ImageInfoSpecific *(*bdrv_get_specific_info)(BlockDriverState *bs);
 
+    BdrvDirtyBitmap *(*bdrv_dirty_bitmap_load)(BlockDriverState *bs,
+                                               const char *name,
+                                               Error **errp);
+
     int (*bdrv_save_vmstate)(BlockDriverState *bs, QEMUIOVector *qiov,
                              int64_t pos);
     int (*bdrv_load_vmstate)(BlockDriverState *bs, uint8_t *buf,