diff --git a/block.c b/block.c
index cb5d7ae..6268e37 100644
--- a/block.c
+++ b/block.c
@@ -85,8 +85,7 @@
 static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
                              const char *reference, QDict *options, int flags,
                              BlockDriverState *parent,
-                             const BdrvChildRole *child_role,
-                             BlockDriver *drv, Error **errp);
+                             const BdrvChildRole *child_role, Error **errp);
 
 static void bdrv_dirty_bitmap_truncate(BlockDriverState *bs);
 /* If non-zero, use only whitelisted block drivers */
@@ -314,13 +313,6 @@
     return 0;
 }
 
-BlockDriver *bdrv_find_whitelisted_format(const char *format_name,
-                                          bool read_only)
-{
-    BlockDriver *drv = bdrv_find_format(format_name);
-    return drv && bdrv_is_whitelisted(drv, read_only) ? drv : NULL;
-}
-
 typedef struct CreateCo {
     BlockDriver *drv;
     char *filename;
@@ -997,13 +989,13 @@
  * block driver has been specified explicitly.
  */
 static int bdrv_fill_options(QDict **options, const char **pfilename,
-                             int *flags, BlockDriver *drv, Error **errp)
+                             int *flags, Error **errp)
 {
     const char *filename = *pfilename;
     const char *drvname;
     bool protocol = *flags & BDRV_O_PROTOCOL;
     bool parse_filename = false;
-    BlockDriver *tmp_drv;
+    BlockDriver *drv = NULL;
     Error *local_err = NULL;
 
     /* Parse json: pseudo-protocol */
@@ -1022,15 +1014,15 @@
     }
 
     drvname = qdict_get_try_str(*options, "driver");
-
-    /* If the user has explicitly specified the driver, this choice should
-     * override the BDRV_O_PROTOCOL flag */
-    tmp_drv = drv;
-    if (!tmp_drv && drvname) {
-        tmp_drv = bdrv_find_format(drvname);
-    }
-    if (tmp_drv) {
-        protocol = tmp_drv->bdrv_file_open;
+    if (drvname) {
+        drv = bdrv_find_format(drvname);
+        if (!drv) {
+            error_setg(errp, "Unknown driver '%s'", drvname);
+            return -ENOENT;
+        }
+        /* If the user has explicitly specified the driver, this choice should
+         * override the BDRV_O_PROTOCOL flag */
+        protocol = drv->bdrv_file_open;
     }
 
     if (protocol) {
@@ -1054,33 +1046,18 @@
     /* Find the right block driver */
     filename = qdict_get_try_str(*options, "filename");
 
-    if (drv) {
-        if (drvname) {
-            error_setg(errp, "Driver specified twice");
-            return -EINVAL;
-        }
-        drvname = drv->format_name;
-        qdict_put(*options, "driver", qstring_from_str(drvname));
-    } else {
-        if (!drvname && protocol) {
-            if (filename) {
-                drv = bdrv_find_protocol(filename, parse_filename, errp);
-                if (!drv) {
-                    return -EINVAL;
-                }
-
-                drvname = drv->format_name;
-                qdict_put(*options, "driver", qstring_from_str(drvname));
-            } else {
-                error_setg(errp, "Must specify either driver or file");
+    if (!drvname && protocol) {
+        if (filename) {
+            drv = bdrv_find_protocol(filename, parse_filename, errp);
+            if (!drv) {
                 return -EINVAL;
             }
-        } else if (drvname) {
-            drv = bdrv_find_format(drvname);
-            if (!drv) {
-                error_setg(errp, "Unknown driver '%s'", drvname);
-                return -ENOENT;
-            }
+
+            drvname = drv->format_name;
+            qdict_put(*options, "driver", qstring_from_str(drvname));
+        } else {
+            error_setg(errp, "Must specify either driver or file");
+            return -EINVAL;
         }
     }
 
@@ -1227,8 +1204,7 @@
     assert(bs->backing_hd == NULL);
     ret = bdrv_open_inherit(&backing_hd,
                             *backing_filename ? backing_filename : NULL,
-                            NULL, options, 0, bs, &child_backing,
-                            NULL, &local_err);
+                            NULL, options, 0, bs, &child_backing, &local_err);
     if (ret < 0) {
         bdrv_unref(backing_hd);
         backing_hd = NULL;
@@ -1291,7 +1267,7 @@
 
     bs = NULL;
     ret = bdrv_open_inherit(&bs, filename, reference, image_options, 0,
-                            parent, child_role, NULL, errp);
+                            parent, child_role, errp);
     if (ret < 0) {
         goto done;
     }
@@ -1385,11 +1361,13 @@
               qstring_from_str("file"));
     qdict_put(snapshot_options, "file.filename",
               qstring_from_str(tmp_filename));
+    qdict_put(snapshot_options, "driver",
+              qstring_from_str("qcow2"));
 
     bs_snapshot = bdrv_new();
 
     ret = bdrv_open(&bs_snapshot, NULL, NULL, snapshot_options,
-                    flags, &bdrv_qcow2, &local_err);
+                    flags, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
@@ -1420,11 +1398,11 @@
 static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
                              const char *reference, QDict *options, int flags,
                              BlockDriverState *parent,
-                             const BdrvChildRole *child_role,
-                             BlockDriver *drv, Error **errp)
+                             const BdrvChildRole *child_role, Error **errp)
 {
     int ret;
     BlockDriverState *file = NULL, *bs;
+    BlockDriver *drv = NULL;
     const char *drvname;
     Error *local_err = NULL;
     int snapshot_flags = 0;
@@ -1474,13 +1452,12 @@
         flags = child_role->inherit_flags(parent->open_flags);
     }
 
-    ret = bdrv_fill_options(&options, &filename, &flags, drv, &local_err);
+    ret = bdrv_fill_options(&options, &filename, &flags, &local_err);
     if (local_err) {
         goto fail;
     }
 
     /* Find the right image format driver */
-    drv = NULL;
     drvname = qdict_get_try_str(options, "driver");
     if (drvname) {
         drv = bdrv_find_format(drvname);
@@ -1635,11 +1612,10 @@
 }
 
 int bdrv_open(BlockDriverState **pbs, const char *filename,
-              const char *reference, QDict *options, int flags,
-              BlockDriver *drv, Error **errp)
+              const char *reference, QDict *options, int flags, Error **errp)
 {
     return bdrv_open_inherit(pbs, filename, reference, options, flags, NULL,
-                             NULL, drv, errp);
+                             NULL, errp);
 }
 
 typedef struct BlockReopenQueueEntry {
@@ -1660,6 +1636,9 @@
  *
  * bs is the BlockDriverState to add to the reopen queue.
  *
+ * options contains the changed options for the associated bs
+ * (the BlockReopenQueue takes ownership)
+ *
  * flags contains the open flags for the associated bs
  *
  * returns a pointer to bs_queue, which is either the newly allocated
@@ -1667,18 +1646,28 @@
  *
  */
 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
-                                    BlockDriverState *bs, int flags)
+                                    BlockDriverState *bs,
+                                    QDict *options, int flags)
 {
     assert(bs != NULL);
 
     BlockReopenQueueEntry *bs_entry;
     BdrvChild *child;
+    QDict *old_options;
 
     if (bs_queue == NULL) {
         bs_queue = g_new0(BlockReopenQueue, 1);
         QSIMPLEQ_INIT(bs_queue);
     }
 
+    if (!options) {
+        options = qdict_new();
+    }
+
+    old_options = qdict_clone_shallow(bs->options);
+    qdict_join(options, old_options, false);
+    QDECREF(old_options);
+
     /* bdrv_open() masks this flag out */
     flags &= ~BDRV_O_PROTOCOL;
 
@@ -1690,13 +1679,15 @@
         }
 
         child_flags = child->role->inherit_flags(flags);
-        bdrv_reopen_queue(bs_queue, child->bs, child_flags);
+        /* TODO Pass down child flags (backing.*, extents.*, ...) */
+        bdrv_reopen_queue(bs_queue, child->bs, NULL, child_flags);
     }
 
     bs_entry = g_new0(BlockReopenQueueEntry, 1);
     QSIMPLEQ_INSERT_TAIL(bs_queue, bs_entry, entry);
 
     bs_entry->state.bs = bs;
+    bs_entry->state.options = options;
     bs_entry->state.flags = flags;
 
     return bs_queue;
@@ -1749,6 +1740,7 @@
         if (ret && bs_entry->prepared) {
             bdrv_reopen_abort(&bs_entry->state);
         }
+        QDECREF(bs_entry->state.options);
         g_free(bs_entry);
     }
     g_free(bs_queue);
@@ -1761,7 +1753,7 @@
 {
     int ret = -1;
     Error *local_err = NULL;
-    BlockReopenQueue *queue = bdrv_reopen_queue(NULL, bs, bdrv_flags);
+    BlockReopenQueue *queue = bdrv_reopen_queue(NULL, bs, NULL, bdrv_flags);
 
     ret = bdrv_reopen_multiple(queue, &local_err);
     if (local_err != NULL) {
@@ -1837,6 +1829,26 @@
         goto error;
     }
 
+    /* Options that are not handled are only okay if they are unchanged
+     * compared to the old state. It is expected that some options are only
+     * used for the initial open, but not reopen (e.g. filename) */
+    if (qdict_size(reopen_state->options)) {
+        const QDictEntry *entry = qdict_first(reopen_state->options);
+
+        do {
+            QString *new_obj = qobject_to_qstring(entry->value);
+            const char *new = qstring_get_str(new_obj);
+            const char *old = qdict_get_try_str(reopen_state->bs->options,
+                                                entry->key);
+
+            if (!old || strcmp(new, old)) {
+                error_setg(errp, "Cannot change the option '%s'", entry->key);
+                ret = -EINVAL;
+                goto error;
+            }
+        } while ((entry = qdict_next(reopen_state->options, entry)));
+    }
+
     ret = 0;
 
 error:
@@ -3739,7 +3751,6 @@
     const char *backing_fmt, *backing_file;
     int64_t size;
     BlockDriver *drv, *proto_drv;
-    BlockDriver *backing_drv = NULL;
     Error *local_err = NULL;
     int ret = 0;
 
@@ -3813,14 +3824,6 @@
     }
 
     backing_fmt = qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT);
-    if (backing_fmt) {
-        backing_drv = bdrv_find_format(backing_fmt);
-        if (!backing_drv) {
-            error_setg(errp, "Unknown backing file format '%s'",
-                       backing_fmt);
-            goto out;
-        }
-    }
 
     // The size for the image must always be specified, with one exception:
     // If we are using a backing file, we can obtain the size from there
@@ -3831,6 +3834,7 @@
             char *full_backing = g_new0(char, PATH_MAX);
             int64_t size;
             int back_flags;
+            QDict *backing_options = NULL;
 
             bdrv_get_full_backing_filename_from_filename(filename, backing_file,
                                                          full_backing, PATH_MAX,
@@ -3844,9 +3848,15 @@
             back_flags =
                 flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
 
+            if (backing_fmt) {
+                backing_options = qdict_new();
+                qdict_put(backing_options, "driver",
+                          qstring_from_str(backing_fmt));
+            }
+
             bs = NULL;
-            ret = bdrv_open(&bs, full_backing, NULL, NULL, back_flags,
-                            backing_drv, &local_err);
+            ret = bdrv_open(&bs, full_backing, NULL, backing_options,
+                            back_flags, &local_err);
             g_free(full_backing);
             if (ret < 0) {
                 goto out;
diff --git a/block/block-backend.c b/block/block-backend.c
index aee8a12..c2e8732 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -126,7 +126,7 @@
         return NULL;
     }
 
-    ret = bdrv_open(&blk->bs, filename, reference, options, flags, NULL, errp);
+    ret = bdrv_open(&blk->bs, filename, reference, options, flags, errp);
     if (ret < 0) {
         blk_unref(blk);
         return NULL;
diff --git a/block/commit.c b/block/commit.c
index 7312a5b..d12e26f 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -236,11 +236,11 @@
 
     /* convert base & overlay_bs to r/w, if necessary */
     if (!(orig_base_flags & BDRV_O_RDWR)) {
-        reopen_queue = bdrv_reopen_queue(reopen_queue, base,
+        reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
                                          orig_base_flags | BDRV_O_RDWR);
     }
     if (!(orig_overlay_flags & BDRV_O_RDWR)) {
-        reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs,
+        reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
                                          orig_overlay_flags | BDRV_O_RDWR);
     }
     if (reopen_queue) {
diff --git a/block/parallels.c b/block/parallels.c
index 046b568..5cd6ec3 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -476,7 +476,7 @@
 
     file = NULL;
     ret = bdrv_open(&file, filename, NULL, NULL,
-                    BDRV_O_RDWR | BDRV_O_PROTOCOL, NULL, &local_err);
+                    BDRV_O_RDWR | BDRV_O_PROTOCOL, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         return ret;
diff --git a/block/qcow.c b/block/qcow.c
index 01fba54..6e35db1 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -793,7 +793,7 @@
 
     qcow_bs = NULL;
     ret = bdrv_open(&qcow_bs, filename, NULL, NULL,
-                    BDRV_O_RDWR | BDRV_O_PROTOCOL, NULL, &local_err);
+                    BDRV_O_RDWR | BDRV_O_PROTOCOL, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto cleanup;
diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index 046f5b8..7b14c5c 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -55,14 +55,14 @@
 static inline void *qcow2_cache_get_table_addr(BlockDriverState *bs,
                     Qcow2Cache *c, int table)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     return (uint8_t *) c->table_array + (size_t) table * s->cluster_size;
 }
 
 static inline int qcow2_cache_get_table_idx(BlockDriverState *bs,
                   Qcow2Cache *c, void *table)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     ptrdiff_t table_offset = (uint8_t *) table - (uint8_t *) c->table_array;
     int idx = table_offset / s->cluster_size;
     assert(idx >= 0 && idx < c->size && table_offset % s->cluster_size == 0);
@@ -73,7 +73,7 @@
                                       int i, int num_tables)
 {
 #if QEMU_MADV_DONTNEED != QEMU_MADV_INVALID
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     void *t = qcow2_cache_get_table_addr(bs, c, i);
     int align = getpagesize();
     size_t mem_size = (size_t) s->cluster_size * num_tables;
@@ -121,7 +121,7 @@
 
 Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     Qcow2Cache *c;
 
     c = g_new0(Qcow2Cache, 1);
@@ -172,7 +172,7 @@
 
 static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret = 0;
 
     if (!c->entries[i].dirty || !c->entries[i].offset) {
@@ -229,7 +229,7 @@
 
 int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int result = 0;
     int ret;
     int i;
@@ -306,7 +306,7 @@
 static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
     uint64_t offset, void **table, bool read_from_disk)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int i;
     int ret;
     int lookup_index;
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 61309ae..6ede629 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -32,7 +32,7 @@
 int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
                         bool exact_size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int new_l1_size2, ret, i;
     uint64_t *new_l1_table;
     int64_t old_l1_table_offset, old_l1_size;
@@ -148,7 +148,7 @@
 static int l2_load(BlockDriverState *bs, uint64_t l2_offset,
     uint64_t **l2_table)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret;
 
     ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, (void**) l2_table);
@@ -163,7 +163,7 @@
 #define L1_ENTRIES_PER_SECTOR (512 / 8)
 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 };
     int l1_start_index;
     int i, ret;
@@ -203,7 +203,7 @@
 
 static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t old_l2_offset;
     uint64_t *l2_table = NULL;
     int64_t l2_offset;
@@ -298,7 +298,7 @@
  * as contiguous. (This allows it, for example, to stop at the first compressed
  * cluster which may require a different handling)
  */
-static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
+static int count_contiguous_clusters(int nb_clusters, int cluster_size,
         uint64_t *l2_table, uint64_t stop_flags)
 {
     int i;
@@ -321,7 +321,7 @@
 	return i;
 }
 
-static int count_contiguous_free_clusters(uint64_t nb_clusters, uint64_t *l2_table)
+static int count_contiguous_free_clusters(int nb_clusters, uint64_t *l2_table)
 {
     int i;
 
@@ -339,7 +339,7 @@
 /* The crypt function is compatible with the linux cryptoloop
    algorithm for < 4 GB images. NOTE: out_buf == in_buf is
    supported */
-int qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
+int qcow2_encrypt_sectors(BDRVQcow2State *s, int64_t sector_num,
                           uint8_t *out_buf, const uint8_t *in_buf,
                           int nb_sectors, bool enc,
                           Error **errp)
@@ -387,7 +387,7 @@
                                      uint64_t cluster_offset,
                                      int n_start, int n_end)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QEMUIOVector qiov;
     struct iovec iov;
     int n, ret;
@@ -469,7 +469,7 @@
 int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
     int *num, uint64_t *cluster_offset)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     unsigned int l2_index;
     uint64_t l1_index, l2_offset, *l2_table;
     int l1_bits, c;
@@ -495,6 +495,7 @@
     if (nb_needed > nb_available) {
         nb_needed = nb_available;
     }
+    assert(nb_needed <= INT_MAX);
 
     *cluster_offset = 0;
 
@@ -530,6 +531,8 @@
 
     l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
     *cluster_offset = be64_to_cpu(l2_table[l2_index]);
+
+    /* nb_needed <= INT_MAX, thus nb_clusters <= INT_MAX, too */
     nb_clusters = size_to_clusters(s, nb_needed << 9);
 
     ret = qcow2_get_cluster_type(*cluster_offset);
@@ -606,7 +609,7 @@
                              uint64_t **new_l2_table,
                              int *new_l2_index)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     unsigned int l2_index;
     uint64_t l1_index, l2_offset;
     uint64_t *l2_table = NULL;
@@ -680,7 +683,7 @@
                                                uint64_t offset,
                                                int compressed_size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int l2_index, ret;
     uint64_t *l2_table;
     int64_t cluster_offset;
@@ -725,7 +728,7 @@
 
 static int perform_cow(BlockDriverState *bs, QCowL2Meta *m, Qcow2COWRegion *r)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret;
 
     if (r->nb_sectors == 0) {
@@ -754,7 +757,7 @@
 
 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int i, j = 0, l2_index, ret;
     uint64_t *old_cluster, *l2_table;
     uint64_t cluster_offset = m->alloc_offset;
@@ -837,7 +840,7 @@
  * write, but require COW to be performed (this includes yet unallocated space,
  * which must copy from the backing file)
  */
-static int count_cow_clusters(BDRVQcowState *s, int nb_clusters,
+static int count_cow_clusters(BDRVQcow2State *s, int nb_clusters,
     uint64_t *l2_table, int l2_index)
 {
     int i;
@@ -883,7 +886,7 @@
 static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset,
     uint64_t *cur_bytes, QCowL2Meta **m)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowL2Meta *old_alloc;
     uint64_t bytes = *cur_bytes;
 
@@ -956,11 +959,11 @@
 static int handle_copied(BlockDriverState *bs, uint64_t guest_offset,
     uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int l2_index;
     uint64_t cluster_offset;
     uint64_t *l2_table;
-    unsigned int nb_clusters;
+    uint64_t nb_clusters;
     unsigned int keep_clusters;
     int ret;
 
@@ -979,6 +982,7 @@
 
     l2_index = offset_to_l2_index(s, guest_offset);
     nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
+    assert(nb_clusters <= INT_MAX);
 
     /* Find L2 entry for the first involved cluster */
     ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index);
@@ -1061,9 +1065,9 @@
  * restarted, but the whole request should not be failed.
  */
 static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset,
-    uint64_t *host_offset, unsigned int *nb_clusters)
+                                   uint64_t *host_offset, uint64_t *nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset,
                                          *host_offset, *nb_clusters);
@@ -1079,7 +1083,7 @@
         *host_offset = cluster_offset;
         return 0;
     } else {
-        int ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters);
+        int64_t ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters);
         if (ret < 0) {
             return ret;
         }
@@ -1111,11 +1115,11 @@
 static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset,
     uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int l2_index;
     uint64_t *l2_table;
     uint64_t entry;
-    unsigned int nb_clusters;
+    uint64_t nb_clusters;
     int ret;
 
     uint64_t alloc_cluster_offset;
@@ -1133,6 +1137,7 @@
 
     l2_index = offset_to_l2_index(s, guest_offset);
     nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
+    assert(nb_clusters <= INT_MAX);
 
     /* Find L2 entry for the first involved cluster */
     ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index);
@@ -1263,7 +1268,7 @@
 int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
     int *num, uint64_t *host_offset, QCowL2Meta **m)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t start, remaining;
     uint64_t cluster_offset;
     uint64_t cur_bytes;
@@ -1397,7 +1402,7 @@
 
 int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret, csize, nb_csectors, sector_offset;
     uint64_t coffset;
 
@@ -1426,9 +1431,10 @@
  * clusters.
  */
 static int discard_single_l2(BlockDriverState *bs, uint64_t offset,
-    unsigned int nb_clusters, enum qcow2_discard_type type, bool full_discard)
+                             uint64_t nb_clusters, enum qcow2_discard_type type,
+                             bool full_discard)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l2_table;
     int l2_index;
     int ret;
@@ -1441,6 +1447,7 @@
 
     /* Limit nb_clusters to one L2 table */
     nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
+    assert(nb_clusters <= INT_MAX);
 
     for (i = 0; i < nb_clusters; i++) {
         uint64_t old_l2_entry;
@@ -1501,9 +1508,9 @@
 int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
     int nb_sectors, enum qcow2_discard_type type, bool full_discard)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t end_offset;
-    unsigned int nb_clusters;
+    uint64_t nb_clusters;
     int ret;
 
     end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS);
@@ -1545,9 +1552,9 @@
  * clusters.
  */
 static int zero_single_l2(BlockDriverState *bs, uint64_t offset,
-    unsigned int nb_clusters)
+                          uint64_t nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l2_table;
     int l2_index;
     int ret;
@@ -1560,6 +1567,7 @@
 
     /* Limit nb_clusters to one L2 table */
     nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
+    assert(nb_clusters <= INT_MAX);
 
     for (i = 0; i < nb_clusters; i++) {
         uint64_t old_offset;
@@ -1583,8 +1591,8 @@
 
 int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors)
 {
-    BDRVQcowState *s = bs->opaque;
-    unsigned int nb_clusters;
+    BDRVQcow2State *s = bs->opaque;
+    uint64_t nb_clusters;
     int ret;
 
     /* The zero flag is only supported by version 3 and newer */
@@ -1628,7 +1636,7 @@
                                       int64_t l1_entries,
                                       BlockDriverAmendStatusCB *status_cb)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     bool is_active_l1 = (l1_table == s->l1_table);
     uint64_t *l2_table = NULL;
     int ret;
@@ -1815,7 +1823,7 @@
 int qcow2_expand_zero_clusters(BlockDriverState *bs,
                                BlockDriverAmendStatusCB *status_cb)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l1_table = NULL;
     int64_t l1_entries = 0, visited_l1_entries = 0;
     int ret;
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index d8f0645..2110839 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -82,7 +82,7 @@
 
 int qcow2_refcount_init(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     unsigned int refcount_table_size2, i;
     int ret;
 
@@ -116,7 +116,7 @@
 
 void qcow2_refcount_close(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     g_free(s->refcount_table);
 }
 
@@ -214,7 +214,7 @@
                                int64_t refcount_block_offset,
                                void **refcount_block)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret;
 
     BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_LOAD);
@@ -231,7 +231,7 @@
 int qcow2_get_refcount(BlockDriverState *bs, int64_t cluster_index,
                        uint64_t *refcount)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t refcount_table_index, block_index;
     int64_t refcount_block_offset;
     int ret;
@@ -274,7 +274,7 @@
  * Rounds the refcount table size up to avoid growing the table for each single
  * refcount block that is allocated.
  */
-static unsigned int next_refcount_table_size(BDRVQcowState *s,
+static unsigned int next_refcount_table_size(BDRVQcow2State *s,
     unsigned int min_size)
 {
     unsigned int min_clusters = (min_size >> (s->cluster_bits - 3)) + 1;
@@ -290,7 +290,7 @@
 
 
 /* Checks if two offsets are described by the same refcount block */
-static int in_same_refcount_block(BDRVQcowState *s, uint64_t offset_a,
+static int in_same_refcount_block(BDRVQcow2State *s, uint64_t offset_a,
     uint64_t offset_b)
 {
     uint64_t block_a = offset_a >> (s->cluster_bits + s->refcount_block_bits);
@@ -308,7 +308,7 @@
 static int alloc_refcount_block(BlockDriverState *bs,
                                 int64_t cluster_index, void **refcount_block)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     unsigned int refcount_table_index;
     int ret;
 
@@ -605,7 +605,7 @@
 
 void qcow2_process_discards(BlockDriverState *bs, int ret)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     Qcow2DiscardRegion *d, *next;
 
     QTAILQ_FOREACH_SAFE(d, &s->discards, next, next) {
@@ -625,7 +625,7 @@
 static void update_refcount_discard(BlockDriverState *bs,
                                     uint64_t offset, uint64_t length)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     Qcow2DiscardRegion *d, *p, *next;
 
     QTAILQ_FOREACH(d, &s->discards, next) {
@@ -682,7 +682,7 @@
                                                    bool decrease,
                                                    enum qcow2_discard_type type)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t start, last, cluster_offset;
     void *refcount_block = NULL;
     int64_t old_table_index = -1;
@@ -793,7 +793,7 @@
                                   uint64_t addend, bool decrease,
                                   enum qcow2_discard_type type)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret;
 
     ret = update_refcount(bs, cluster_index << s->cluster_bits, 1, addend,
@@ -815,7 +815,7 @@
 /* return < 0 if error */
 static int64_t alloc_clusters_noref(BlockDriverState *bs, uint64_t size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t i, nb_clusters, refcount;
     int ret;
 
@@ -875,10 +875,10 @@
     return offset;
 }
 
-int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
-    int nb_clusters)
+int64_t qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
+                                int64_t nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t cluster_index, refcount;
     uint64_t i;
     int ret;
@@ -916,7 +916,7 @@
    contiguous sectors. size must be <= cluster_size */
 int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t offset;
     size_t free_in_cluster;
     int ret;
@@ -949,11 +949,17 @@
 
             if (!offset || ROUND_UP(offset, s->cluster_size) != new_cluster) {
                 offset = new_cluster;
+                free_in_cluster = s->cluster_size;
+            } else {
+                free_in_cluster += s->cluster_size;
             }
         }
 
         assert(offset);
         ret = update_refcount(bs, offset, size, 1, false, QCOW2_DISCARD_NEVER);
+        if (ret < 0) {
+            offset = 0;
+        }
     } while (ret == -EAGAIN);
     if (ret < 0) {
         return ret;
@@ -992,7 +998,7 @@
 void qcow2_free_any_clusters(BlockDriverState *bs, uint64_t l2_entry,
                              int nb_clusters, enum qcow2_discard_type type)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     switch (qcow2_get_cluster_type(l2_entry)) {
     case QCOW2_CLUSTER_COMPRESSED:
@@ -1036,7 +1042,7 @@
 int qcow2_update_snapshot_refcount(BlockDriverState *bs,
     int64_t l1_table_offset, int l1_size, int addend)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2, refcount;
     bool l1_allocated = false;
     int64_t old_offset, old_l2_offset;
@@ -1233,7 +1239,7 @@
 /* refcount checking functions */
 
 
-static size_t refcount_array_byte_size(BDRVQcowState *s, uint64_t entries)
+static size_t refcount_array_byte_size(BDRVQcow2State *s, uint64_t entries)
 {
     /* This assertion holds because there is no way we can address more than
      * 2^(64 - 9) clusters at once (with cluster size 512 = 2^9, and because
@@ -1256,10 +1262,10 @@
  * refcount array buffer will be aligned to a cluster boundary, and the newly
  * allocated area will be zeroed.
  */
-static int realloc_refcount_array(BDRVQcowState *s, void **array,
+static int realloc_refcount_array(BDRVQcow2State *s, void **array,
                                   int64_t *size, int64_t new_size)
 {
-    size_t old_byte_size, new_byte_size;
+    int64_t old_byte_size, new_byte_size;
     void *new_ptr;
 
     /* Round to clusters so the array can be directly written to disk */
@@ -1275,13 +1281,17 @@
 
     assert(new_byte_size > 0);
 
+    if (new_byte_size > SIZE_MAX) {
+        return -ENOMEM;
+    }
+
     new_ptr = g_try_realloc(*array, new_byte_size);
     if (!new_ptr) {
         return -ENOMEM;
     }
 
     if (new_byte_size > old_byte_size) {
-        memset((void *)((uintptr_t)new_ptr + old_byte_size), 0,
+        memset((char *)new_ptr + old_byte_size, 0,
                new_byte_size - old_byte_size);
     }
 
@@ -1304,7 +1314,7 @@
                          int64_t *refcount_table_size,
                          int64_t offset, int64_t size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t start, last, cluster_offset, k, refcount;
     int ret;
 
@@ -1357,7 +1367,7 @@
                               int64_t *refcount_table_size, int64_t l2_offset,
                               int flags)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l2_table, l2_entry;
     uint64_t next_contiguous_offset = 0;
     int i, l2_size, nb_csectors, ret;
@@ -1477,7 +1487,7 @@
                               int64_t l1_table_offset, int l1_size,
                               int flags)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l1_table = NULL, l2_offset, l1_size2;
     int i, ret;
 
@@ -1554,7 +1564,7 @@
 static int check_oflag_copied(BlockDriverState *bs, BdrvCheckResult *res,
                               BdrvCheckMode fix)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t *l2_table = qemu_blockalign(bs, s->cluster_size);
     int ret;
     uint64_t refcount;
@@ -1673,7 +1683,7 @@
                            BdrvCheckMode fix, bool *rebuild,
                            void **refcount_table, int64_t *nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t i, size;
     int ret;
 
@@ -1776,7 +1786,7 @@
                                BdrvCheckMode fix, bool *rebuild,
                                void **refcount_table, int64_t *nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t i;
     QCowSnapshot *sn;
     int ret;
@@ -1840,7 +1850,7 @@
                               int64_t *highest_cluster,
                               void *refcount_table, int64_t nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t i;
     uint64_t refcount1, refcount2;
     int ret;
@@ -1917,7 +1927,7 @@
                                    int64_t *imrt_nb_clusters,
                                    int64_t *first_free_cluster)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t cluster = *first_free_cluster, i;
     bool first_gap = true;
     int contiguous_free_clusters;
@@ -1987,7 +1997,7 @@
                                       void **refcount_table,
                                       int64_t *nb_clusters)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t first_free_cluster = 0, reftable_offset = -1, cluster = 0;
     int64_t refblock_offset, refblock_start, refblock_index;
     uint32_t reftable_size = 0;
@@ -2174,7 +2184,7 @@
 int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
                           BdrvCheckMode fix)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     BdrvCheckResult pre_compare_res;
     int64_t size, highest_cluster, nb_clusters;
     void *refcount_table = NULL;
@@ -2311,7 +2321,7 @@
 int qcow2_check_metadata_overlap(BlockDriverState *bs, int ign, int64_t offset,
                                  int64_t size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int chk = s->overlap_check & ~ign;
     int i, j;
 
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index b6f58c1..92f4dfc 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -29,7 +29,7 @@
 
 void qcow2_free_snapshots(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int i;
 
     for(i = 0; i < s->nb_snapshots; i++) {
@@ -43,7 +43,7 @@
 
 int qcow2_read_snapshots(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshotHeader h;
     QCowSnapshotExtraData extra;
     QCowSnapshot *sn;
@@ -136,7 +136,7 @@
 /* add at the end of the file a new list of snapshots */
 static int qcow2_write_snapshots(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshot *sn;
     QCowSnapshotHeader h;
     QCowSnapshotExtraData extra;
@@ -278,7 +278,7 @@
 static void find_new_snapshot_id(BlockDriverState *bs,
                                  char *id_str, int id_str_size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshot *sn;
     int i;
     unsigned long id, id_max = 0;
@@ -296,7 +296,7 @@
                                         const char *id,
                                         const char *name)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int i;
 
     if (id && name) {
@@ -338,7 +338,7 @@
 /* if no id is provided, a new one is constructed */
 int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshot *new_snapshot_list = NULL;
     QCowSnapshot *old_snapshot_list = NULL;
     QCowSnapshot sn1, *sn = &sn1;
@@ -461,7 +461,7 @@
 /* copy the snapshot 'snapshot_name' into the current disk image */
 int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshot *sn;
     int i, snapshot_index;
     int cur_l1_bytes, sn_l1_bytes;
@@ -587,7 +587,7 @@
                           const char *name,
                           Error **errp)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshot sn;
     int snapshot_index, ret;
 
@@ -650,7 +650,7 @@
 
 int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QEMUSnapshotInfo *sn_tab, *sn_info;
     QCowSnapshot *sn;
     int i;
@@ -683,7 +683,7 @@
                             Error **errp)
 {
     int i, snapshot_index;
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowSnapshot *sn;
     uint64_t *new_l1_table;
     int new_l1_bytes;
diff --git a/block/qcow2.c b/block/qcow2.c
index ea34ae2..56ad808 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -85,7 +85,7 @@
                                  uint64_t end_offset, void **p_feature_table,
                                  Error **errp)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowExtension ext;
     uint64_t offset;
     int ret;
@@ -187,7 +187,7 @@
 
 static void cleanup_unknown_header_ext(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     Qcow2UnknownHeaderExtension *uext, *next;
 
     QLIST_FOREACH_SAFE(uext, &s->unknown_header_ext, next, next) {
@@ -249,7 +249,7 @@
  */
 int qcow2_mark_dirty(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t val;
     int ret;
 
@@ -282,7 +282,7 @@
  */
 static int qcow2_mark_clean(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     if (s->incompatible_features & QCOW2_INCOMPAT_DIRTY) {
         int ret;
@@ -304,7 +304,7 @@
  */
 int qcow2_mark_corrupt(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     s->incompatible_features |= QCOW2_INCOMPAT_CORRUPT;
     return qcow2_update_header(bs);
@@ -316,7 +316,7 @@
  */
 int qcow2_mark_consistent(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     if (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT) {
         int ret = bdrv_flush(bs);
@@ -351,7 +351,7 @@
 static int validate_table_offset(BlockDriverState *bs, uint64_t offset,
                                  uint64_t entries, size_t entry_len)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t size;
 
     /* Use signed INT64_MAX as the maximum even for uint64_t header fields,
@@ -490,7 +490,7 @@
 static void cache_clean_timer_cb(void *opaque)
 {
     BlockDriverState *bs = opaque;
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     qcow2_cache_clean_unused(bs, s->l2_table_cache);
     qcow2_cache_clean_unused(bs, s->refcount_block_cache);
     timer_mod(s->cache_clean_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
@@ -499,7 +499,7 @@
 
 static void cache_clean_timer_init(BlockDriverState *bs, AioContext *context)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     if (s->cache_clean_interval > 0) {
         s->cache_clean_timer = aio_timer_new(context, QEMU_CLOCK_VIRTUAL,
                                              SCALE_MS, cache_clean_timer_cb,
@@ -511,7 +511,7 @@
 
 static void cache_clean_timer_del(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     if (s->cache_clean_timer) {
         timer_del(s->cache_clean_timer);
         timer_free(s->cache_clean_timer);
@@ -534,7 +534,7 @@
                              uint64_t *l2_cache_size,
                              uint64_t *refcount_cache_size, Error **errp)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t combined_cache_size;
     bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set;
 
@@ -589,21 +589,244 @@
     }
 }
 
-static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
-                      Error **errp)
+typedef struct Qcow2ReopenState {
+    Qcow2Cache *l2_table_cache;
+    Qcow2Cache *refcount_block_cache;
+    bool use_lazy_refcounts;
+    int overlap_check;
+    bool discard_passthrough[QCOW2_DISCARD_MAX];
+    uint64_t cache_clean_interval;
+} Qcow2ReopenState;
+
+static int qcow2_update_options_prepare(BlockDriverState *bs,
+                                        Qcow2ReopenState *r,
+                                        QDict *options, int flags,
+                                        Error **errp)
 {
-    BDRVQcowState *s = bs->opaque;
-    unsigned int len, i;
-    int ret = 0;
-    QCowHeader header;
+    BDRVQcow2State *s = bs->opaque;
     QemuOpts *opts = NULL;
-    Error *local_err = NULL;
-    uint64_t ext_end;
-    uint64_t l1_vm_state_index;
     const char *opt_overlap_check, *opt_overlap_check_template;
     int overlap_check_template = 0;
     uint64_t l2_cache_size, refcount_cache_size;
-    uint64_t cache_clean_interval;
+    int i;
+    Error *local_err = NULL;
+    int ret;
+
+    opts = qemu_opts_create(&qcow2_runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    /* get L2 table/refcount block cache size from command line options */
+    read_cache_sizes(bs, opts, &l2_cache_size, &refcount_cache_size,
+                     &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    l2_cache_size /= s->cluster_size;
+    if (l2_cache_size < MIN_L2_CACHE_SIZE) {
+        l2_cache_size = MIN_L2_CACHE_SIZE;
+    }
+    if (l2_cache_size > INT_MAX) {
+        error_setg(errp, "L2 cache size too big");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    refcount_cache_size /= s->cluster_size;
+    if (refcount_cache_size < MIN_REFCOUNT_CACHE_SIZE) {
+        refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE;
+    }
+    if (refcount_cache_size > INT_MAX) {
+        error_setg(errp, "Refcount cache size too big");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    /* alloc new L2 table/refcount block cache, flush old one */
+    if (s->l2_table_cache) {
+        ret = qcow2_cache_flush(bs, s->l2_table_cache);
+        if (ret) {
+            error_setg_errno(errp, -ret, "Failed to flush the L2 table cache");
+            goto fail;
+        }
+    }
+
+    if (s->refcount_block_cache) {
+        ret = qcow2_cache_flush(bs, s->refcount_block_cache);
+        if (ret) {
+            error_setg_errno(errp, -ret,
+                             "Failed to flush the refcount block cache");
+            goto fail;
+        }
+    }
+
+    r->l2_table_cache = qcow2_cache_create(bs, l2_cache_size);
+    r->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size);
+    if (r->l2_table_cache == NULL || r->refcount_block_cache == NULL) {
+        error_setg(errp, "Could not allocate metadata caches");
+        ret = -ENOMEM;
+        goto fail;
+    }
+
+    /* New interval for cache cleanup timer */
+    r->cache_clean_interval =
+        qemu_opt_get_number(opts, QCOW2_OPT_CACHE_CLEAN_INTERVAL,
+                            s->cache_clean_interval);
+    if (r->cache_clean_interval > UINT_MAX) {
+        error_setg(errp, "Cache clean interval too big");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    /* lazy-refcounts; flush if going from enabled to disabled */
+    r->use_lazy_refcounts = qemu_opt_get_bool(opts, QCOW2_OPT_LAZY_REFCOUNTS,
+        (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS));
+    if (r->use_lazy_refcounts && s->qcow_version < 3) {
+        error_setg(errp, "Lazy refcounts require a qcow2 image with at least "
+                   "qemu 1.1 compatibility level");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    if (s->use_lazy_refcounts && !r->use_lazy_refcounts) {
+        ret = qcow2_mark_clean(bs);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret, "Failed to disable lazy refcounts");
+            goto fail;
+        }
+    }
+
+    /* Overlap check options */
+    opt_overlap_check = qemu_opt_get(opts, QCOW2_OPT_OVERLAP);
+    opt_overlap_check_template = qemu_opt_get(opts, QCOW2_OPT_OVERLAP_TEMPLATE);
+    if (opt_overlap_check_template && opt_overlap_check &&
+        strcmp(opt_overlap_check_template, opt_overlap_check))
+    {
+        error_setg(errp, "Conflicting values for qcow2 options '"
+                   QCOW2_OPT_OVERLAP "' ('%s') and '" QCOW2_OPT_OVERLAP_TEMPLATE
+                   "' ('%s')", opt_overlap_check, opt_overlap_check_template);
+        ret = -EINVAL;
+        goto fail;
+    }
+    if (!opt_overlap_check) {
+        opt_overlap_check = opt_overlap_check_template ?: "cached";
+    }
+
+    if (!strcmp(opt_overlap_check, "none")) {
+        overlap_check_template = 0;
+    } else if (!strcmp(opt_overlap_check, "constant")) {
+        overlap_check_template = QCOW2_OL_CONSTANT;
+    } else if (!strcmp(opt_overlap_check, "cached")) {
+        overlap_check_template = QCOW2_OL_CACHED;
+    } else if (!strcmp(opt_overlap_check, "all")) {
+        overlap_check_template = QCOW2_OL_ALL;
+    } else {
+        error_setg(errp, "Unsupported value '%s' for qcow2 option "
+                   "'overlap-check'. Allowed are any of the following: "
+                   "none, constant, cached, all", opt_overlap_check);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    r->overlap_check = 0;
+    for (i = 0; i < QCOW2_OL_MAX_BITNR; i++) {
+        /* overlap-check defines a template bitmask, but every flag may be
+         * overwritten through the associated boolean option */
+        r->overlap_check |=
+            qemu_opt_get_bool(opts, overlap_bool_option_names[i],
+                              overlap_check_template & (1 << i)) << i;
+    }
+
+    r->discard_passthrough[QCOW2_DISCARD_NEVER] = false;
+    r->discard_passthrough[QCOW2_DISCARD_ALWAYS] = true;
+    r->discard_passthrough[QCOW2_DISCARD_REQUEST] =
+        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_REQUEST,
+                          flags & BDRV_O_UNMAP);
+    r->discard_passthrough[QCOW2_DISCARD_SNAPSHOT] =
+        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_SNAPSHOT, true);
+    r->discard_passthrough[QCOW2_DISCARD_OTHER] =
+        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_OTHER, false);
+
+    ret = 0;
+fail:
+    qemu_opts_del(opts);
+    opts = NULL;
+    return ret;
+}
+
+static void qcow2_update_options_commit(BlockDriverState *bs,
+                                        Qcow2ReopenState *r)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int i;
+
+    if (s->l2_table_cache) {
+        qcow2_cache_destroy(bs, s->l2_table_cache);
+    }
+    if (s->refcount_block_cache) {
+        qcow2_cache_destroy(bs, s->refcount_block_cache);
+    }
+    s->l2_table_cache = r->l2_table_cache;
+    s->refcount_block_cache = r->refcount_block_cache;
+
+    s->overlap_check = r->overlap_check;
+    s->use_lazy_refcounts = r->use_lazy_refcounts;
+
+    for (i = 0; i < QCOW2_DISCARD_MAX; i++) {
+        s->discard_passthrough[i] = r->discard_passthrough[i];
+    }
+
+    if (s->cache_clean_interval != r->cache_clean_interval) {
+        cache_clean_timer_del(bs);
+        s->cache_clean_interval = r->cache_clean_interval;
+        cache_clean_timer_init(bs, bdrv_get_aio_context(bs));
+    }
+}
+
+static void qcow2_update_options_abort(BlockDriverState *bs,
+                                       Qcow2ReopenState *r)
+{
+    if (r->l2_table_cache) {
+        qcow2_cache_destroy(bs, r->l2_table_cache);
+    }
+    if (r->refcount_block_cache) {
+        qcow2_cache_destroy(bs, r->refcount_block_cache);
+    }
+}
+
+static int qcow2_update_options(BlockDriverState *bs, QDict *options,
+                                int flags, Error **errp)
+{
+    Qcow2ReopenState r = {};
+    int ret;
+
+    ret = qcow2_update_options_prepare(bs, &r, options, flags, errp);
+    if (ret >= 0) {
+        qcow2_update_options_commit(bs, &r);
+    } else {
+        qcow2_update_options_abort(bs, &r);
+    }
+
+    return ret;
+}
+
+static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
+                      Error **errp)
+{
+    BDRVQcow2State *s = bs->opaque;
+    unsigned int len, i;
+    int ret = 0;
+    QCowHeader header;
+    Error *local_err = NULL;
+    uint64_t ext_end;
+    uint64_t l1_vm_state_index;
 
     ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
     if (ret < 0) {
@@ -851,62 +1074,12 @@
         }
     }
 
-    /* get L2 table/refcount block cache size from command line options */
-    opts = qemu_opts_create(&qcow2_runtime_opts, NULL, 0, &error_abort);
-    qemu_opts_absorb_qdict(opts, options, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        ret = -EINVAL;
+    /* Parse driver-specific options */
+    ret = qcow2_update_options(bs, options, flags, errp);
+    if (ret < 0) {
         goto fail;
     }
 
-    read_cache_sizes(bs, opts, &l2_cache_size, &refcount_cache_size,
-                     &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        ret = -EINVAL;
-        goto fail;
-    }
-
-    l2_cache_size /= s->cluster_size;
-    if (l2_cache_size < MIN_L2_CACHE_SIZE) {
-        l2_cache_size = MIN_L2_CACHE_SIZE;
-    }
-    if (l2_cache_size > INT_MAX) {
-        error_setg(errp, "L2 cache size too big");
-        ret = -EINVAL;
-        goto fail;
-    }
-
-    refcount_cache_size /= s->cluster_size;
-    if (refcount_cache_size < MIN_REFCOUNT_CACHE_SIZE) {
-        refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE;
-    }
-    if (refcount_cache_size > INT_MAX) {
-        error_setg(errp, "Refcount cache size too big");
-        ret = -EINVAL;
-        goto fail;
-    }
-
-    /* alloc L2 table/refcount block cache */
-    s->l2_table_cache = qcow2_cache_create(bs, l2_cache_size);
-    s->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size);
-    if (s->l2_table_cache == NULL || s->refcount_block_cache == NULL) {
-        error_setg(errp, "Could not allocate metadata caches");
-        ret = -ENOMEM;
-        goto fail;
-    }
-
-    cache_clean_interval =
-        qemu_opt_get_number(opts, QCOW2_OPT_CACHE_CLEAN_INTERVAL, 0);
-    if (cache_clean_interval > UINT_MAX) {
-        error_setg(errp, "Cache clean interval too big");
-        ret = -EINVAL;
-        goto fail;
-    }
-    s->cache_clean_interval = cache_clean_interval;
-    cache_clean_timer_init(bs, bdrv_get_aio_context(bs));
-
     s->cluster_cache = g_malloc(s->cluster_size);
     /* one more sector for decompressed data alignment */
     s->cluster_data = qemu_try_blockalign(bs->file, QCOW_MAX_CRYPT_CLUSTERS
@@ -991,70 +1164,6 @@
         }
     }
 
-    /* Enable lazy_refcounts according to image and command line options */
-    s->use_lazy_refcounts = qemu_opt_get_bool(opts, QCOW2_OPT_LAZY_REFCOUNTS,
-        (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS));
-
-    s->discard_passthrough[QCOW2_DISCARD_NEVER] = false;
-    s->discard_passthrough[QCOW2_DISCARD_ALWAYS] = true;
-    s->discard_passthrough[QCOW2_DISCARD_REQUEST] =
-        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_REQUEST,
-                          flags & BDRV_O_UNMAP);
-    s->discard_passthrough[QCOW2_DISCARD_SNAPSHOT] =
-        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_SNAPSHOT, true);
-    s->discard_passthrough[QCOW2_DISCARD_OTHER] =
-        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_OTHER, false);
-
-    opt_overlap_check = qemu_opt_get(opts, QCOW2_OPT_OVERLAP);
-    opt_overlap_check_template = qemu_opt_get(opts, QCOW2_OPT_OVERLAP_TEMPLATE);
-    if (opt_overlap_check_template && opt_overlap_check &&
-        strcmp(opt_overlap_check_template, opt_overlap_check))
-    {
-        error_setg(errp, "Conflicting values for qcow2 options '"
-                   QCOW2_OPT_OVERLAP "' ('%s') and '" QCOW2_OPT_OVERLAP_TEMPLATE
-                   "' ('%s')", opt_overlap_check, opt_overlap_check_template);
-        ret = -EINVAL;
-        goto fail;
-    }
-    if (!opt_overlap_check) {
-        opt_overlap_check = opt_overlap_check_template ?: "cached";
-    }
-
-    if (!strcmp(opt_overlap_check, "none")) {
-        overlap_check_template = 0;
-    } else if (!strcmp(opt_overlap_check, "constant")) {
-        overlap_check_template = QCOW2_OL_CONSTANT;
-    } else if (!strcmp(opt_overlap_check, "cached")) {
-        overlap_check_template = QCOW2_OL_CACHED;
-    } else if (!strcmp(opt_overlap_check, "all")) {
-        overlap_check_template = QCOW2_OL_ALL;
-    } else {
-        error_setg(errp, "Unsupported value '%s' for qcow2 option "
-                   "'overlap-check'. Allowed are either of the following: "
-                   "none, constant, cached, all", opt_overlap_check);
-        ret = -EINVAL;
-        goto fail;
-    }
-
-    s->overlap_check = 0;
-    for (i = 0; i < QCOW2_OL_MAX_BITNR; i++) {
-        /* overlap-check defines a template bitmask, but every flag may be
-         * overwritten through the associated boolean option */
-        s->overlap_check |=
-            qemu_opt_get_bool(opts, overlap_bool_option_names[i],
-                              overlap_check_template & (1 << i)) << i;
-    }
-
-    qemu_opts_del(opts);
-    opts = NULL;
-
-    if (s->use_lazy_refcounts && s->qcow_version < 3) {
-        error_setg(errp, "Lazy refcounts require a qcow2 image with at least "
-                   "qemu 1.1 compatibility level");
-        ret = -EINVAL;
-        goto fail;
-    }
-
 #ifdef DEBUG_ALLOC
     {
         BdrvCheckResult result = {0};
@@ -1064,7 +1173,6 @@
     return ret;
 
  fail:
-    qemu_opts_del(opts);
     g_free(s->unknown_header_fields);
     cleanup_unknown_header_ext(bs);
     qcow2_free_snapshots(bs);
@@ -1086,14 +1194,14 @@
 
 static void qcow2_refresh_limits(BlockDriverState *bs, Error **errp)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     bs->bl.write_zeroes_alignment = s->cluster_sectors;
 }
 
 static int qcow2_set_key(BlockDriverState *bs, const char *key)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint8_t keybuf[16];
     int len, i;
     Error *err = NULL;
@@ -1126,32 +1234,58 @@
     return 0;
 }
 
-/* We have no actual commit/abort logic for qcow2, but we need to write out any
- * unwritten data if we reopen read-only. */
 static int qcow2_reopen_prepare(BDRVReopenState *state,
                                 BlockReopenQueue *queue, Error **errp)
 {
+    Qcow2ReopenState *r;
     int ret;
 
+    r = g_new0(Qcow2ReopenState, 1);
+    state->opaque = r;
+
+    ret = qcow2_update_options_prepare(state->bs, r, state->options,
+                                       state->flags, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    /* We need to write out any unwritten data if we reopen read-only. */
     if ((state->flags & BDRV_O_RDWR) == 0) {
         ret = bdrv_flush(state->bs);
         if (ret < 0) {
-            return ret;
+            goto fail;
         }
 
         ret = qcow2_mark_clean(state->bs);
         if (ret < 0) {
-            return ret;
+            goto fail;
         }
     }
 
     return 0;
+
+fail:
+    qcow2_update_options_abort(state->bs, r);
+    g_free(r);
+    return ret;
+}
+
+static void qcow2_reopen_commit(BDRVReopenState *state)
+{
+    qcow2_update_options_commit(state->bs, state->opaque);
+    g_free(state->opaque);
+}
+
+static void qcow2_reopen_abort(BDRVReopenState *state)
+{
+    qcow2_update_options_abort(state->bs, state->opaque);
+    g_free(state->opaque);
 }
 
 static int64_t coroutine_fn qcow2_co_get_block_status(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, int *pnum)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t cluster_offset;
     int index_in_cluster, ret;
     int64_t status = 0;
@@ -1198,7 +1332,7 @@
 static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
                           int remaining_sectors, QEMUIOVector *qiov)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int index_in_cluster, n1;
     int ret;
     int cur_nr_sectors; /* number of sectors in current iteration */
@@ -1360,7 +1494,7 @@
                            int remaining_sectors,
                            QEMUIOVector *qiov)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int index_in_cluster;
     int ret;
     int cur_nr_sectors; /* number of sectors in current iteration */
@@ -1506,7 +1640,7 @@
 
 static void qcow2_close(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     qemu_vfree(s->l1_table);
     /* else pre-write overlap checks in cache_destroy may crash */
     s->l1_table = NULL;
@@ -1552,7 +1686,7 @@
 
 static void qcow2_invalidate_cache(BlockDriverState *bs, Error **errp)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int flags = s->flags;
     QCryptoCipher *cipher = NULL;
     QDict *options;
@@ -1575,7 +1709,7 @@
         return;
     }
 
-    memset(s, 0, sizeof(BDRVQcowState));
+    memset(s, 0, sizeof(BDRVQcow2State));
     options = qdict_clone_shallow(bs->options);
 
     ret = qcow2_open(bs, options, flags, &local_err);
@@ -1622,7 +1756,7 @@
  */
 int qcow2_update_header(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     QCowHeader *header;
     char *buf;
     size_t buflen = s->cluster_size;
@@ -1791,7 +1925,7 @@
 static int qcow2_change_backing_file(BlockDriverState *bs,
     const char *backing_file, const char *backing_fmt)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
     pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: "");
@@ -1873,8 +2007,10 @@
                          QemuOpts *opts, int version, int refcount_order,
                          Error **errp)
 {
-    /* Calculate cluster_bits */
     int cluster_bits;
+    QDict *options;
+
+    /* Calculate cluster_bits */
     cluster_bits = ctz32(cluster_size);
     if (cluster_bits < MIN_CLUSTER_BITS || cluster_bits > MAX_CLUSTER_BITS ||
         (1 << cluster_bits) != cluster_size)
@@ -1973,7 +2109,7 @@
 
     bs = NULL;
     ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, &local_err);
+                    &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         return ret;
@@ -2032,9 +2168,11 @@
      * refcount of the cluster that is occupied by the header and the refcount
      * table)
      */
-    ret = bdrv_open(&bs, filename, NULL, NULL,
+    options = qdict_new();
+    qdict_put(options, "driver", qstring_from_str("qcow2"));
+    ret = bdrv_open(&bs, filename, NULL, options,
                     BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH,
-                    &bdrv_qcow2, &local_err);
+                    &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
@@ -2070,7 +2208,7 @@
 
     /* And if we're supposed to preallocate metadata, do that now */
     if (prealloc != PREALLOC_MODE_OFF) {
-        BDRVQcowState *s = bs->opaque;
+        BDRVQcow2State *s = bs->opaque;
         qemu_co_mutex_lock(&s->lock);
         ret = preallocate(bs);
         qemu_co_mutex_unlock(&s->lock);
@@ -2084,9 +2222,11 @@
     bs = NULL;
 
     /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
-    ret = bdrv_open(&bs, filename, NULL, NULL,
+    options = qdict_new();
+    qdict_put(options, "driver", qstring_from_str("qcow2"));
+    ret = bdrv_open(&bs, filename, NULL, options,
                     BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_BACKING,
-                    &bdrv_qcow2, &local_err);
+                    &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         goto out;
@@ -2203,7 +2343,7 @@
     int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
 {
     int ret;
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     /* Emulate misaligned zero writes */
     if (sector_num % s->cluster_sectors || nb_sectors % s->cluster_sectors) {
@@ -2223,7 +2363,7 @@
     int64_t sector_num, int nb_sectors)
 {
     int ret;
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
 
     qemu_co_mutex_lock(&s->lock);
     ret = qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS,
@@ -2234,7 +2374,7 @@
 
 static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t new_l1_size;
     int ret;
 
@@ -2278,7 +2418,7 @@
 static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
                                   const uint8_t *buf, int nb_sectors)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     z_stream strm;
     int ret, out_len;
     uint8_t *out_buf;
@@ -2369,7 +2509,7 @@
 
 static int make_completely_empty(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret, l1_clusters;
     int64_t offset;
     uint64_t *new_reftable = NULL;
@@ -2517,7 +2657,7 @@
 
 static int qcow2_make_empty(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     uint64_t start_sector;
     int sector_step = INT_MAX / BDRV_SECTOR_SIZE;
     int l1_clusters, ret = 0;
@@ -2558,7 +2698,7 @@
 
 static coroutine_fn int qcow2_co_flush_to_os(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int ret;
 
     qemu_co_mutex_lock(&s->lock);
@@ -2582,7 +2722,7 @@
 
 static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     bdi->unallocated_blocks_are_zero = true;
     bdi->can_write_zeroes_with_unmap = (s->qcow_version >= 3);
     bdi->cluster_size = s->cluster_size;
@@ -2592,7 +2732,7 @@
 
 static ImageInfoSpecific *qcow2_get_specific_info(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     ImageInfoSpecific *spec_info = g_new(ImageInfoSpecific, 1);
 
     *spec_info = (ImageInfoSpecific){
@@ -2625,7 +2765,7 @@
 #if 0
 static void dump_refcounts(BlockDriverState *bs)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t nb_clusters, k, k1, size;
     int refcount;
 
@@ -2646,7 +2786,7 @@
 static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
                               int64_t pos)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int64_t total_sectors = bs->total_sectors;
     bool zero_beyond_eof = bs->zero_beyond_eof;
     int ret;
@@ -2667,7 +2807,7 @@
 static int qcow2_load_vmstate(BlockDriverState *bs, uint8_t *buf,
                               int64_t pos, int size)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     bool zero_beyond_eof = bs->zero_beyond_eof;
     int ret;
 
@@ -2686,7 +2826,7 @@
 static int qcow2_downgrade(BlockDriverState *bs, int target_version,
                            BlockDriverAmendStatusCB *status_cb)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int current_version = s->qcow_version;
     int ret;
 
@@ -2750,7 +2890,7 @@
 static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
                                BlockDriverAmendStatusCB *status_cb)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     int old_version = s->qcow_version, new_version = old_version;
     uint64_t new_size = 0;
     const char *backing_file = NULL, *backing_format = NULL;
@@ -2897,7 +3037,7 @@
 void qcow2_signal_corruption(BlockDriverState *bs, bool fatal, int64_t offset,
                              int64_t size, const char *message_format, ...)
 {
-    BDRVQcowState *s = bs->opaque;
+    BDRVQcow2State *s = bs->opaque;
     const char *node_name;
     char *message;
     va_list ap;
@@ -2998,11 +3138,13 @@
 
 BlockDriver bdrv_qcow2 = {
     .format_name        = "qcow2",
-    .instance_size      = sizeof(BDRVQcowState),
+    .instance_size      = sizeof(BDRVQcow2State),
     .bdrv_probe         = qcow2_probe,
     .bdrv_open          = qcow2_open,
     .bdrv_close         = qcow2_close,
     .bdrv_reopen_prepare  = qcow2_reopen_prepare,
+    .bdrv_reopen_commit   = qcow2_reopen_commit,
+    .bdrv_reopen_abort    = qcow2_reopen_abort,
     .bdrv_create        = qcow2_create,
     .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_get_block_status = qcow2_co_get_block_status,
diff --git a/block/qcow2.h b/block/qcow2.h
index 71dafd6..d700bf1 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -222,7 +222,7 @@
 typedef void Qcow2SetRefcountFunc(void *refcount_array,
                                   uint64_t index, uint64_t value);
 
-typedef struct BDRVQcowState {
+typedef struct BDRVQcow2State {
     int cluster_bits;
     int cluster_size;
     int cluster_sectors;
@@ -293,7 +293,7 @@
      * override) */
     char *image_backing_file;
     char *image_backing_format;
-} BDRVQcowState;
+} BDRVQcow2State;
 
 struct QCowAIOCB;
 
@@ -405,28 +405,28 @@
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
 
-static inline int64_t start_of_cluster(BDRVQcowState *s, int64_t offset)
+static inline int64_t start_of_cluster(BDRVQcow2State *s, int64_t offset)
 {
     return offset & ~(s->cluster_size - 1);
 }
 
-static inline int64_t offset_into_cluster(BDRVQcowState *s, int64_t offset)
+static inline int64_t offset_into_cluster(BDRVQcow2State *s, int64_t offset)
 {
     return offset & (s->cluster_size - 1);
 }
 
-static inline int size_to_clusters(BDRVQcowState *s, int64_t size)
+static inline uint64_t size_to_clusters(BDRVQcow2State *s, uint64_t size)
 {
     return (size + (s->cluster_size - 1)) >> s->cluster_bits;
 }
 
-static inline int64_t size_to_l1(BDRVQcowState *s, int64_t size)
+static inline int64_t size_to_l1(BDRVQcow2State *s, int64_t size)
 {
     int shift = s->cluster_bits + s->l2_bits;
     return (size + (1ULL << shift) - 1) >> shift;
 }
 
-static inline int offset_to_l2_index(BDRVQcowState *s, int64_t offset)
+static inline int offset_to_l2_index(BDRVQcow2State *s, int64_t offset)
 {
     return (offset >> s->cluster_bits) & (s->l2_size - 1);
 }
@@ -437,12 +437,12 @@
     return offset;
 }
 
-static inline int64_t qcow2_vm_state_offset(BDRVQcowState *s)
+static inline int64_t qcow2_vm_state_offset(BDRVQcow2State *s)
 {
     return (int64_t)s->l1_vm_state_index << (s->cluster_bits + s->l2_bits);
 }
 
-static inline uint64_t qcow2_max_refcount_clusters(BDRVQcowState *s)
+static inline uint64_t qcow2_max_refcount_clusters(BDRVQcow2State *s)
 {
     return QCOW_MAX_REFTABLE_SIZE >> s->cluster_bits;
 }
@@ -461,7 +461,7 @@
 }
 
 /* Check whether refcounts are eager or lazy */
-static inline bool qcow2_need_accurate_refcounts(BDRVQcowState *s)
+static inline bool qcow2_need_accurate_refcounts(BDRVQcow2State *s)
 {
     return !(s->incompatible_features & QCOW2_INCOMPAT_DIRTY);
 }
@@ -509,8 +509,8 @@
                                   enum qcow2_discard_type type);
 
 int64_t qcow2_alloc_clusters(BlockDriverState *bs, uint64_t size);
-int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
-    int nb_clusters);
+int64_t qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
+                                int64_t nb_clusters);
 int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size);
 void qcow2_free_clusters(BlockDriverState *bs,
                           int64_t offset, int64_t size,
@@ -537,7 +537,7 @@
 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index);
 void qcow2_l2_cache_reset(BlockDriverState *bs);
 int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset);
-int qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
+int qcow2_encrypt_sectors(BDRVQcow2State *s, int64_t sector_num,
                           uint8_t *out_buf, const uint8_t *in_buf,
                           int nb_sectors, bool enc, Error **errp);
 
diff --git a/block/qed.c b/block/qed.c
index 954ed00..a7ff1d9 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -583,7 +583,7 @@
 
     bs = NULL;
     ret = bdrv_open(&bs, filename, NULL, NULL,
-                    BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL, NULL,
+                    BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_PROTOCOL,
                     &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 9585beb..67ca788 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1554,7 +1554,7 @@
     int ret;
 
     ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, errp);
+                    errp);
     if (ret < 0) {
         goto out_with_err_set;
     }
@@ -1746,8 +1746,7 @@
         }
 
         bs = NULL;
-        ret = bdrv_open(&bs, backing_file, NULL, NULL, BDRV_O_PROTOCOL, NULL,
-                        errp);
+        ret = bdrv_open(&bs, backing_file, NULL, NULL, BDRV_O_PROTOCOL, errp);
         if (ret < 0) {
             goto out;
         }
diff --git a/block/vdi.c b/block/vdi.c
index 7642ef3..062a654 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -764,7 +764,7 @@
         goto exit;
     }
     ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, &local_err);
+                    &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto exit;
diff --git a/block/vhdx.c b/block/vhdx.c
index f05c7a9..d3bb1bd 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1842,7 +1842,7 @@
 
     bs = NULL;
     ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, &local_err);
+                    &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto exit;
diff --git a/block/vmdk.c b/block/vmdk.c
index fbaab67..be0d640 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1324,8 +1324,12 @@
 
     write_end_sector = DIV_ROUND_UP(write_offset + write_len, BDRV_SECTOR_SIZE);
 
-    extent->next_cluster_sector = MAX(extent->next_cluster_sector,
-                                      write_end_sector);
+    if (extent->compressed) {
+        extent->next_cluster_sector = write_end_sector;
+    } else {
+        extent->next_cluster_sector = MAX(extent->next_cluster_sector,
+                                          write_end_sector);
+    }
 
     if (ret != write_len) {
         ret = ret < 0 ? ret : -EIO;
@@ -1632,7 +1636,7 @@
 
     assert(bs == NULL);
     ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, &local_err);
+                    &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto exit;
@@ -1905,8 +1909,7 @@
             ret = -ENOENT;
             goto exit;
         }
-        ret = bdrv_open(&bs, full_backing, NULL, NULL, BDRV_O_NO_BACKING, NULL,
-                        errp);
+        ret = bdrv_open(&bs, full_backing, NULL, NULL, BDRV_O_NO_BACKING, errp);
         g_free(full_backing);
         if (ret != 0) {
             goto exit;
@@ -1977,7 +1980,7 @@
     }
     assert(new_bs == NULL);
     ret = bdrv_open(&new_bs, filename, NULL, NULL,
-                    BDRV_O_RDWR | BDRV_O_PROTOCOL, NULL, &local_err);
+                    BDRV_O_RDWR | BDRV_O_PROTOCOL, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto exit;
diff --git a/block/vpc.c b/block/vpc.c
index 3e385d9..2b3b518 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -794,7 +794,7 @@
         goto out;
     }
     ret = bdrv_open(&bs, filename, NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
-                    NULL, &local_err);
+                    &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
diff --git a/block/vvfat.c b/block/vvfat.c
index 2068697..7ddc962 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -2926,6 +2926,8 @@
     QemuOpts *opts = NULL;
     int ret;
     int size = sector2cluster(s, s->sector_count);
+    QDict *options;
+
     s->used_clusters = calloc(size, 1);
 
     array_init(&(s->commits), sizeof(commit_t));
@@ -2956,9 +2958,11 @@
     }
 
     s->qcow = NULL;
-    ret = bdrv_open(&s->qcow, s->qcow_filename, NULL, NULL,
+    options = qdict_new();
+    qdict_put(options, "driver", qstring_from_str("qcow"));
+    ret = bdrv_open(&s->qcow, s->qcow_filename, NULL, options,
                     BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH,
-                    bdrv_qcow, errp);
+                    errp);
     if (ret < 0) {
         goto err;
     }
diff --git a/blockdev.c b/blockdev.c
index 6b48be6..32b04b4 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1422,9 +1422,8 @@
 static void external_snapshot_prepare(BlkTransactionState *common,
                                       Error **errp)
 {
-    BlockDriver *drv;
     int flags, ret;
-    QDict *options = NULL;
+    QDict *options;
     Error *local_err = NULL;
     bool has_device = false;
     const char *device;
@@ -1459,12 +1458,6 @@
     }
 
     /* start processing */
-    drv = bdrv_find_format(format);
-    if (!drv) {
-        error_setg(errp, QERR_INVALID_BLOCK_FORMAT, format);
-        return;
-    }
-
     state->old_bs = bdrv_lookup_bs(has_device ? device : NULL,
                                    has_node_name ? node_name : NULL,
                                    &local_err);
@@ -1523,17 +1516,18 @@
         }
     }
 
+    options = qdict_new();
     if (has_snapshot_node_name) {
-        options = qdict_new();
         qdict_put(options, "node-name",
                   qstring_from_str(snapshot_node_name));
     }
+    qdict_put(options, "driver", qstring_from_str(format));
 
     /* TODO Inherit bs->options or only take explicit options with an
      * extended QMP command? */
     assert(state->new_bs == NULL);
     ret = bdrv_open(&state->new_bs, new_image_file, NULL, options,
-                    flags | BDRV_O_NO_BACKING, drv, &local_err);
+                    flags | BDRV_O_NO_BACKING, &local_err);
     /* We will manually add the backing_hd field to the bs later */
     if (ret != 0) {
         error_propagate(errp, local_err);
@@ -1895,13 +1889,19 @@
 
 /* Assumes AioContext is held */
 static void qmp_bdrv_open_encrypted(BlockDriverState *bs, const char *filename,
-                                    int bdrv_flags, BlockDriver *drv,
+                                    int bdrv_flags, const char *format,
                                     const char *password, Error **errp)
 {
     Error *local_err = NULL;
+    QDict *options = NULL;
     int ret;
 
-    ret = bdrv_open(&bs, filename, NULL, NULL, bdrv_flags, drv, &local_err);
+    if (format) {
+        options = qdict_new();
+        qdict_put(options, "driver", qstring_from_str(format));
+    }
+
+    ret = bdrv_open(&bs, filename, NULL, options, bdrv_flags, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         return;
@@ -1916,7 +1916,6 @@
     BlockBackend *blk;
     BlockDriverState *bs;
     AioContext *aio_context;
-    BlockDriver *drv = NULL;
     int bdrv_flags;
     Error *err = NULL;
 
@@ -1931,14 +1930,6 @@
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    if (format) {
-        drv = bdrv_find_whitelisted_format(format, bs->read_only);
-        if (!drv) {
-            error_setg(errp, QERR_INVALID_BLOCK_FORMAT, format);
-            goto out;
-        }
-    }
-
     eject_device(blk, 0, &err);
     if (err) {
         error_propagate(errp, err);
@@ -1948,7 +1939,7 @@
     bdrv_flags = bdrv_is_read_only(bs) ? 0 : BDRV_O_RDWR;
     bdrv_flags |= bdrv_is_snapshot(bs) ? BDRV_O_SNAPSHOT : 0;
 
-    qmp_bdrv_open_encrypted(bs, filename, bdrv_flags, drv, NULL, errp);
+    qmp_bdrv_open_encrypted(bs, filename, bdrv_flags, format, NULL, errp);
 
 out:
     aio_context_release(aio_context);
@@ -2466,7 +2457,7 @@
     BlockDriverState *source = NULL;
     BdrvDirtyBitmap *bmap = NULL;
     AioContext *aio_context;
-    BlockDriver *drv = NULL;
+    QDict *options = NULL;
     Error *local_err = NULL;
     int flags;
     int64_t size;
@@ -2506,13 +2497,6 @@
     if (!has_format) {
         format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : bs->drv->format_name;
     }
-    if (format) {
-        drv = bdrv_find_format(format);
-        if (!drv) {
-            error_setg(errp, QERR_INVALID_BLOCK_FORMAT, format);
-            goto out;
-        }
-    }
 
     /* Early check to avoid creating target */
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
@@ -2540,7 +2524,7 @@
     }
 
     if (mode != NEW_IMAGE_MODE_EXISTING) {
-        assert(format && drv);
+        assert(format);
         if (source) {
             bdrv_img_create(target, format, source->filename,
                             source->drv->format_name, NULL,
@@ -2556,8 +2540,13 @@
         goto out;
     }
 
+    if (format) {
+        options = qdict_new();
+        qdict_put(options, "driver", qstring_from_str(format));
+    }
+
     target_bs = NULL;
-    ret = bdrv_open(&target_bs, target, NULL, NULL, flags, drv, &local_err);
+    ret = bdrv_open(&target_bs, target, NULL, options, flags, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
@@ -2663,9 +2652,8 @@
     BlockDriverState *bs;
     BlockDriverState *source, *target_bs;
     AioContext *aio_context;
-    BlockDriver *drv = NULL;
     Error *local_err = NULL;
-    QDict *options = NULL;
+    QDict *options;
     int flags;
     int64_t size;
     int ret;
@@ -2722,13 +2710,6 @@
     if (!has_format) {
         format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : bs->drv->format_name;
     }
-    if (format) {
-        drv = bdrv_find_format(format);
-        if (!drv) {
-            error_setg(errp, QERR_INVALID_BLOCK_FORMAT, format);
-            goto out;
-        }
-    }
 
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_MIRROR, errp)) {
         goto out;
@@ -2783,7 +2764,7 @@
         && mode != NEW_IMAGE_MODE_EXISTING)
     {
         /* create new image w/o backing file */
-        assert(format && drv);
+        assert(format);
         bdrv_img_create(target, format,
                         NULL, NULL, NULL, size, flags, &local_err, false);
     } else {
@@ -2807,17 +2788,20 @@
         goto out;
     }
 
+    options = qdict_new();
     if (has_node_name) {
-        options = qdict_new();
         qdict_put(options, "node-name", qstring_from_str(node_name));
     }
+    if (format) {
+        qdict_put(options, "driver", qstring_from_str(format));
+    }
 
     /* Mirroring takes care of copy-on-write using the source's backing
      * file.
      */
     target_bs = NULL;
     ret = bdrv_open(&target_bs, target, NULL, options,
-                    flags | BDRV_O_NO_BACKING, drv, &local_err);
+                    flags | BDRV_O_NO_BACKING, &local_err);
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto out;
diff --git a/include/block/block.h b/include/block/block.h
index 0acd104..ef67353 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -147,6 +147,7 @@
 typedef struct BDRVReopenState {
     BlockDriverState *bs;
     int flags;
+    QDict *options;
     void *opaque;
 } BDRVReopenState;
 
@@ -193,8 +194,6 @@
                                 bool allow_protocol_prefix,
                                 Error **errp);
 BlockDriver *bdrv_find_format(const char *format_name);
-BlockDriver *bdrv_find_whitelisted_format(const char *format_name,
-                                          bool readonly);
 int bdrv_create(BlockDriver *drv, const char* filename,
                 QemuOpts *opts, Error **errp);
 int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp);
@@ -218,10 +217,10 @@
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp);
 int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp);
 int bdrv_open(BlockDriverState **pbs, const char *filename,
-              const char *reference, QDict *options, int flags,
-              BlockDriver *drv, Error **errp);
+              const char *reference, QDict *options, int flags, Error **errp);
 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
-                                    BlockDriverState *bs, int flags);
+                                    BlockDriverState *bs,
+                                    QDict *options, int flags);
 int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp);
 int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp);
 int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 53477e1..d6572a8 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1979,6 +1979,95 @@
        .oneline        = "prints the allocated areas of a file",
 };
 
+static void reopen_help(void)
+{
+    printf(
+"\n"
+" Changes the open options of an already opened image\n"
+"\n"
+" Example:\n"
+" 'reopen -o lazy-refcounts=on' - activates lazy refcount writeback on a qcow2 image\n"
+"\n"
+" -r, -- Reopen the image read-only\n"
+" -c, -- Change the cache mode to the given value\n"
+" -o, -- Changes block driver options (cf. 'open' command)\n"
+"\n");
+}
+
+static int reopen_f(BlockBackend *blk, int argc, char **argv);
+
+static QemuOptsList reopen_opts = {
+    .name = "reopen",
+    .merge_lists = true,
+    .head = QTAILQ_HEAD_INITIALIZER(reopen_opts.head),
+    .desc = {
+        /* no elements => accept any params */
+        { /* end of list */ }
+    },
+};
+
+static const cmdinfo_t reopen_cmd = {
+       .name           = "reopen",
+       .argmin         = 0,
+       .argmax         = -1,
+       .cfunc          = reopen_f,
+       .args           = "[-r] [-c cache] [-o options]",
+       .oneline        = "reopens an image with new options",
+       .help           = reopen_help,
+};
+
+static int reopen_f(BlockBackend *blk, int argc, char **argv)
+{
+    BlockDriverState *bs = blk_bs(blk);
+    QemuOpts *qopts;
+    QDict *opts;
+    int c;
+    int flags = bs->open_flags;
+
+    BlockReopenQueue *brq;
+    Error *local_err = NULL;
+
+    while ((c = getopt(argc, argv, "c:o:r")) != -1) {
+        switch (c) {
+        case 'c':
+            if (bdrv_parse_cache_flags(optarg, &flags) < 0) {
+                error_report("Invalid cache option: %s", optarg);
+                return 0;
+            }
+            break;
+        case 'o':
+            if (!qemu_opts_parse_noisily(&reopen_opts, optarg, 0)) {
+                qemu_opts_reset(&reopen_opts);
+                return 0;
+            }
+            break;
+        case 'r':
+            flags &= ~BDRV_O_RDWR;
+            break;
+        default:
+            qemu_opts_reset(&reopen_opts);
+            return qemuio_command_usage(&reopen_cmd);
+        }
+    }
+
+    if (optind != argc) {
+        qemu_opts_reset(&reopen_opts);
+        return qemuio_command_usage(&reopen_cmd);
+    }
+
+    qopts = qemu_opts_find(&reopen_opts, NULL);
+    opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : NULL;
+    qemu_opts_reset(&reopen_opts);
+
+    brq = bdrv_reopen_queue(NULL, bs, opts, flags);
+    bdrv_reopen_multiple(brq, &local_err);
+    if (local_err) {
+        error_report_err(local_err);
+    }
+
+    return 0;
+}
+
 static int break_f(BlockBackend *blk, int argc, char **argv)
 {
     int ret;
@@ -2266,6 +2355,7 @@
     qemuio_add_command(&discard_cmd);
     qemuio_add_command(&alloc_cmd);
     qemuio_add_command(&map_cmd);
+    qemuio_add_command(&reopen_cmd);
     qemuio_add_command(&break_cmd);
     qemuio_add_command(&remove_break_cmd);
     qemuio_add_command(&resume_cmd);
diff --git a/qemu-io.c b/qemu-io.c
index f1e3a67..269f17c 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -156,7 +156,6 @@
             break;
         case 'o':
             if (!qemu_opts_parse_noisily(&empty_opts, optarg, false)) {
-                printf("could not parse option list -- %s\n", optarg);
                 qemu_opts_reset(&empty_opts);
                 return 0;
             }
diff --git a/tests/qemu-iotests/039 b/tests/qemu-iotests/039
index 617f397..9e9b379 100755
--- a/tests/qemu-iotests/039
+++ b/tests/qemu-iotests/039
@@ -147,6 +147,33 @@
 _check_test_img
 TEST_IMG="$TEST_IMG".base _check_test_img
 
+echo
+echo "== Changing lazy_refcounts setting at runtime =="
+
+IMGOPTS="compat=1.1,lazy_refcounts=off"
+_make_test_img $size
+
+$QEMU_IO -c "reopen -o lazy-refcounts=on" \
+         -c "write -P 0x5a 0 512" \
+         -c "sigraise $(kill -l KILL)" "$TEST_IMG" 2>&1 \
+    | _filter_qemu_io
+
+# The dirty bit must be set
+$PYTHON qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
+_check_test_img
+
+IMGOPTS="compat=1.1,lazy_refcounts=on"
+_make_test_img $size
+
+$QEMU_IO -c "reopen -o lazy-refcounts=off" \
+         -c "write -P 0x5a 0 512" \
+         -c "sigraise $(kill -l KILL)" "$TEST_IMG" 2>&1 \
+    | _filter_qemu_io
+
+# The dirty bit must not be set
+$PYTHON qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
+_check_test_img
+
 
 # success, all done
 echo "*** done"
diff --git a/tests/qemu-iotests/039.out b/tests/qemu-iotests/039.out
index d8c5a44..03a31c5 100644
--- a/tests/qemu-iotests/039.out
+++ b/tests/qemu-iotests/039.out
@@ -74,4 +74,22 @@
 incompatible_features     0x0
 No errors were found on the image.
 No errors were found on the image.
+
+== Changing lazy_refcounts setting at runtime ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
+wrote 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+./common.config: Killed                  ( exec "$QEMU_IO_PROG" $QEMU_IO_OPTIONS "$@" )
+incompatible_features     0x1
+ERROR cluster 5 refcount=0 reference=1
+ERROR OFLAG_COPIED data cluster: l2_entry=8000000000050000 refcount=0
+
+2 errors were found on the image.
+Data may be corrupted, or further writes to the image may corrupt it.
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
+wrote 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+./common.config: Killed                  ( exec "$QEMU_IO_PROG" $QEMU_IO_OPTIONS "$@" )
+incompatible_features     0x0
+No errors were found on the image.
 *** done
diff --git a/tests/qemu-iotests/137 b/tests/qemu-iotests/137
new file mode 100755
index 0000000..9a6597c
--- /dev/null
+++ b/tests/qemu-iotests/137
@@ -0,0 +1,145 @@
+#!/bin/bash
+#
+# Test qcow2 reopen
+#
+# Copyright (C) 2015 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+. ./common.qemu
+
+_supported_fmt qcow2
+_supported_proto generic
+_supported_os Linux
+
+
+_make_test_img 64M
+
+echo === Try setting valid values for all options ===
+echo
+
+# Try all options and then check that all of the basic I/O operations still
+# work on this image.
+$QEMU_IO \
+    -c "reopen -o lazy-refcounts=on,pass-discard-request=on" \
+    -c "reopen -o lazy-refcounts=off,pass-discard-request=off" \
+    -c "reopen -o pass-discard-snapshot=on,pass-discard-other=on" \
+    -c "reopen -o pass-discard-snapshot=off,pass-discard-other=off" \
+    -c "reopen -o overlap-check=all" \
+    -c "reopen -o overlap-check=none" \
+    -c "reopen -o overlap-check=cached" \
+    -c "reopen -o overlap-check=constant" \
+    -c "reopen -o overlap-check.template=all" \
+    -c "reopen -o overlap-check.template=none" \
+    -c "reopen -o overlap-check.template=cached" \
+    -c "reopen -o overlap-check.template=constant" \
+    -c "reopen -o overlap-check.main-header=on" \
+    -c "reopen -o overlap-check.main-header=off" \
+    -c "reopen -o overlap-check.active-l1=on" \
+    -c "reopen -o overlap-check.active-l1=off" \
+    -c "reopen -o overlap-check.active-l2=on" \
+    -c "reopen -o overlap-check.active-l2=off" \
+    -c "reopen -o overlap-check.refcount-table=on" \
+    -c "reopen -o overlap-check.refcount-table=off" \
+    -c "reopen -o overlap-check.refcount-block=on" \
+    -c "reopen -o overlap-check.refcount-block=off" \
+    -c "reopen -o overlap-check.snapshot-table=on" \
+    -c "reopen -o overlap-check.snapshot-table=off" \
+    -c "reopen -o overlap-check.inactive-l1=on" \
+    -c "reopen -o overlap-check.inactive-l1=off" \
+    -c "reopen -o overlap-check.inactive-l2=on" \
+    -c "reopen -o overlap-check.inactive-l2=off" \
+    -c "reopen -o cache-size=1M" \
+    -c "reopen -o l2-cache-size=512k" \
+    -c "reopen -o refcount-cache-size=128k" \
+    -c "reopen -o cache-clean-interval=5" \
+    -c "reopen -o cache-clean-interval=0" \
+    -c "reopen -o cache-clean-interval=10" \
+    \
+    -c "write -P 55 0 32M" \
+    -c "read -P 55 0 32M" \
+    -c "discard 0 32M" \
+    -c "write -z 0 32M" \
+    -c "read -P 0 0 32M" \
+    \
+    "$TEST_IMG" | _filter_qemu_io
+
+
+echo
+echo === Try setting some invalid values ===
+echo
+
+$QEMU_IO \
+    -c "reopen -o lazy-refcounts=42" \
+    -c "reopen -o cache-size=1M,l2-cache-size=64k,refcount-cache-size=64k" \
+    -c "reopen -o cache-size=1M,l2-cache-size=2M" \
+    -c "reopen -o cache-size=1M,refcount-cache-size=2M" \
+    -c "reopen -o l2-cache-size=256T" \
+    -c "reopen -o refcount-cache-size=256T" \
+    -c "reopen -o overlap-check=constant,overlap-check.template=all" \
+    -c "reopen -o overlap-check=blubb" \
+    -c "reopen -o overlap-check.template=blubb" \
+    -c "reopen -o cache-clean-interval=-1" \
+    "$TEST_IMG" | _filter_qemu_io
+
+echo
+echo === Test transaction semantics ===
+echo
+
+# Whether lazy-refcounts was actually enabled can easily be tested: Check if
+# the dirty bit is set after a crash
+$QEMU_IO \
+    -c "reopen -o lazy-refcounts=on,overlap-check=blubb" \
+    -c "write -P 0x5a 0 512" \
+    -c "sigraise $(kill -l KILL)" \
+    "$TEST_IMG" 2>&1 | _filter_qemu_io
+
+# The dirty bit must not be set
+$PYTHON qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
+
+# Similarly we can test whether corruption detection has been enabled:
+# Create L1/L2, overwrite first entry in refcount block, allocate something.
+# Disabling the checks should fail, so the corruption must be detected.
+_make_test_img 64M
+$QEMU_IO -c "write 0 64k" "$TEST_IMG" | _filter_qemu_io
+poke_file "$TEST_IMG" "$((0x20000))" "\x00\x00"
+$QEMU_IO \
+    -c "reopen -o overlap-check=none,lazy-refcounts=42" \
+    -c "write 64k 64k" \
+    "$TEST_IMG" 2>&1 | _filter_qemu_io
+
+# success, all done
+echo '*** done'
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/137.out b/tests/qemu-iotests/137.out
new file mode 100644
index 0000000..cf55a41
--- /dev/null
+++ b/tests/qemu-iotests/137.out
@@ -0,0 +1,42 @@
+QA output created by 137
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+=== Try setting valid values for all options ===
+
+wrote 33554432/33554432 bytes at offset 0
+32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 33554432/33554432 bytes at offset 0
+32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 33554432/33554432 bytes at offset 0
+32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 33554432/33554432 bytes at offset 0
+32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 33554432/33554432 bytes at offset 0
+32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Try setting some invalid values ===
+
+Parameter 'lazy-refcounts' expects 'on' or 'off'
+cache-size, l2-cache-size and refcount-cache-size may not be set the same time
+l2-cache-size may not exceed cache-size
+refcount-cache-size may not exceed cache-size
+L2 cache size too big
+L2 cache size too big
+Conflicting values for qcow2 options 'overlap-check' ('constant') and 'overlap-check.template' ('all')
+Unsupported value 'blubb' for qcow2 option 'overlap-check'. Allowed are any of the following: none, constant, cached, all
+Unsupported value 'blubb' for qcow2 option 'overlap-check'. Allowed are any of the following: none, constant, cached, all
+Cache clean interval too big
+
+=== Test transaction semantics ===
+
+Unsupported value 'blubb' for qcow2 option 'overlap-check'. Allowed are any of the following: none, constant, cached, all
+wrote 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+./common.config: Killed                  ( exec "$QEMU_IO_PROG" $QEMU_IO_OPTIONS "$@" )
+incompatible_features     0x0
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+Parameter 'lazy-refcounts' expects 'on' or 'off'
+qcow2: Marking image as corrupt: Preventing invalid write on metadata (overlaps with qcow2_header); further corruption events will be suppressed
+write failed: Input/output error
+*** done
diff --git a/tests/qemu-iotests/138 b/tests/qemu-iotests/138
new file mode 100755
index 0000000..a5c3464
--- /dev/null
+++ b/tests/qemu-iotests/138
@@ -0,0 +1,73 @@
+#!/bin/bash
+#
+# General test case for qcow2's image check
+#
+# Copyright (C) 2015 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=mreitz@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+# This tests qocw2-specific low-level functionality
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+
+echo
+echo '=== Check on an image with a multiple of 2^32 clusters ==='
+echo
+
+IMGOPTS=$(_optstr_add "$IMGOPTS" "cluster_size=512") \
+    _make_test_img 512
+
+# Allocate L2 table
+$QEMU_IO -c 'write 0 512' "$TEST_IMG" | _filter_qemu_io
+
+# Put the data cluster at a multiple of 2 TB, resulting in the image apparently
+# having a multiple of 2^32 clusters
+# (To be more specific: It is at 32 PB)
+poke_file "$TEST_IMG" 2048 "\x80\x80\x00\x00\x00\x00\x00\x00"
+
+# An offset of 32 PB results in qemu-img check having to allocate an in-memory
+# refcount table of 128 TB (16 bit refcounts, 512 byte clusters).
+# This should be generally too much for any system and thus fail.
+# What this test is checking is that the qcow2 driver actually tries to allocate
+# such a large amount of memory (and is consequently aborting) instead of having
+# truncated the cluster count somewhere (which would result in much less memory
+# being allocated and then a segfault occurring).
+_check_test_img
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/138.out b/tests/qemu-iotests/138.out
new file mode 100644
index 0000000..3fe911f
--- /dev/null
+++ b/tests/qemu-iotests/138.out
@@ -0,0 +1,9 @@
+QA output created by 138
+
+=== Check on an image with a multiple of 2^32 clusters ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=512
+wrote 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-img: Check failed: Cannot allocate memory
+*** done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index c430b6c..439b1d2 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -134,3 +134,5 @@
 132 rw auto quick
 134 rw auto quick
 135 rw auto
+137 rw auto
+138 rw auto quick