]> git.proxmox.com Git - mirror_qemu.git/blobdiff - block.c
usb-host: wire up timer for windows
[mirror_qemu.git] / block.c
diff --git a/block.c b/block.c
index 75a82af64117f04670ff4479078bcc135b3d7fd3..e97ce0b1c83eb68db8abccfe90867afb2e8542cb 100644 (file)
--- a/block.c
+++ b/block.c
@@ -54,7 +54,7 @@
 #ifdef CONFIG_BSD
 #include <sys/ioctl.h>
 #include <sys/queue.h>
-#ifndef __DragonFly__
+#if defined(HAVE_SYS_DISK_H)
 #include <sys/disk.h>
 #endif
 #endif
@@ -84,20 +84,15 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
 
 static void bdrv_replace_child_noperm(BdrvChild *child,
                                       BlockDriverState *new_bs);
-static int bdrv_attach_child_noperm(BlockDriverState *parent_bs,
-                                    BlockDriverState *child_bs,
-                                    const char *child_name,
-                                    const BdrvChildClass *child_class,
-                                    BdrvChildRole child_role,
-                                    BdrvChild **child,
-                                    Transaction *tran,
-                                    Error **errp);
+static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
+                                              BdrvChild *child,
+                                              Transaction *tran);
 static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
                                             Transaction *tran);
 
 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
                                BlockReopenQueue *queue,
-                               Transaction *set_backings_tran, Error **errp);
+                               Transaction *change_child_tran, Error **errp);
 static void bdrv_reopen_commit(BDRVReopenState *reopen_state);
 static void bdrv_reopen_abort(BDRVReopenState *reopen_state);
 
@@ -265,7 +260,7 @@ void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
  * image is inactivated. */
 bool bdrv_is_read_only(BlockDriverState *bs)
 {
-    return bs->read_only;
+    return !(bs->open_flags & BDRV_O_RDWR);
 }
 
 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
@@ -317,7 +312,6 @@ int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
         goto fail;
     }
 
-    bs->read_only = true;
     bs->open_flags &= ~BDRV_O_RDWR;
 
     return 0;
@@ -1158,7 +1152,7 @@ int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough)
 static char *bdrv_child_get_parent_desc(BdrvChild *c)
 {
     BlockDriverState *parent = c->opaque;
-    return g_strdup(bdrv_get_device_or_node_name(parent));
+    return g_strdup_printf("node '%s'", bdrv_get_node_name(parent));
 }
 
 static void bdrv_child_cb_drained_begin(BdrvChild *child)
@@ -1412,7 +1406,7 @@ static int bdrv_child_cb_update_filename(BdrvChild *c, BlockDriverState *base,
     return 0;
 }
 
-static AioContext *bdrv_child_cb_get_parent_aio_context(BdrvChild *c)
+AioContext *child_of_bds_get_parent_aio_context(BdrvChild *c)
 {
     BlockDriverState *bs = c->opaque;
 
@@ -1432,7 +1426,7 @@ const BdrvChildClass child_of_bds = {
     .can_set_aio_ctx = bdrv_child_cb_can_set_aio_ctx,
     .set_aio_ctx     = bdrv_child_cb_set_aio_ctx,
     .update_filename = bdrv_child_cb_update_filename,
-    .get_parent_aio_context = bdrv_child_cb_get_parent_aio_context,
+    .get_parent_aio_context = child_of_bds_get_parent_aio_context,
 };
 
 AioContext *bdrv_child_get_parent_aio_context(BdrvChild *c)
@@ -1549,7 +1543,6 @@ static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv,
     }
 
     bs->drv = drv;
-    bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
     bs->opaque = g_malloc0(drv->instance_size);
 
     if (drv->bdrv_file_open) {
@@ -1720,6 +1713,7 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
     QemuOpts *opts;
     BlockDriver *drv;
     Error *local_err = NULL;
+    bool ro;
 
     assert(bs->file == NULL);
     assert(options != NULL && bs->options != options);
@@ -1770,17 +1764,17 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
     trace_bdrv_open_common(bs, filename ?: "", bs->open_flags,
                            drv->format_name);
 
-    bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
+    ro = bdrv_is_read_only(bs);
 
-    if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, bs->read_only)) {
-        if (!bs->read_only && bdrv_is_whitelisted(drv, true)) {
+    if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, ro)) {
+        if (!ro && bdrv_is_whitelisted(drv, true)) {
             ret = bdrv_apply_auto_read_only(bs, NULL, NULL);
         } else {
             ret = -ENOTSUP;
         }
         if (ret < 0) {
             error_setg(errp,
-                       !bs->read_only && bdrv_is_whitelisted(drv, true)
+                       !ro && bdrv_is_whitelisted(drv, true)
                        ? "Driver '%s' can only be used for read-only devices"
                        : "Driver '%s' is not whitelisted",
                        drv->format_name);
@@ -1792,7 +1786,7 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
     assert(qatomic_read(&bs->copy_on_read) == 0);
 
     if (bs->open_flags & BDRV_O_COPY_ON_READ) {
-        if (!bs->read_only) {
+        if (!ro) {
             bdrv_enable_copy_on_read(bs);
         } else {
             error_setg(errp, "Can't use copy-on-read on read-only device");
@@ -2035,27 +2029,38 @@ bool bdrv_is_writable(BlockDriverState *bs)
 
 static char *bdrv_child_user_desc(BdrvChild *c)
 {
-    if (c->klass->get_parent_desc) {
-        return c->klass->get_parent_desc(c);
-    }
-
-    return g_strdup("another user");
+    return c->klass->get_parent_desc(c);
 }
 
+/*
+ * Check that @a allows everything that @b needs. @a and @b must reference same
+ * child node.
+ */
 static bool bdrv_a_allow_b(BdrvChild *a, BdrvChild *b, Error **errp)
 {
-    g_autofree char *user = NULL;
-    g_autofree char *perm_names = NULL;
+    const char *child_bs_name;
+    g_autofree char *a_user = NULL;
+    g_autofree char *b_user = NULL;
+    g_autofree char *perms = NULL;
+
+    assert(a->bs);
+    assert(a->bs == b->bs);
 
     if ((b->perm & a->shared_perm) == b->perm) {
         return true;
     }
 
-    perm_names = bdrv_perm_names(b->perm & ~a->shared_perm);
-    user = bdrv_child_user_desc(a);
-    error_setg(errp, "Conflicts with use by %s as '%s', which does not "
-               "allow '%s' on %s",
-               user, a->name, perm_names, bdrv_get_node_name(b->bs));
+    child_bs_name = bdrv_get_node_name(b->bs);
+    a_user = bdrv_child_user_desc(a);
+    b_user = bdrv_child_user_desc(b);
+    perms = bdrv_perm_names(b->perm & ~a->shared_perm);
+
+    error_setg(errp, "Permission conflict on node '%s': permissions '%s' are "
+               "both required by %s (uses node '%s' as '%s' child) and "
+               "unshared by %s (uses node '%s' as '%s' child).",
+               child_bs_name, perms,
+               b_user, child_bs_name, b->name,
+               a_user, child_bs_name, a->name);
 
     return false;
 }
@@ -2247,12 +2252,14 @@ static TransactionActionDrv bdrv_replace_child_drv = {
 };
 
 /*
- * bdrv_replace_child
+ * bdrv_replace_child_tran
  *
  * Note: real unref of old_bs is done only on commit.
+ *
+ * The function doesn't update permissions, caller is responsible for this.
  */
-static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs,
-                               Transaction *tran)
+static void bdrv_replace_child_tran(BdrvChild *child, BlockDriverState *new_bs,
+                                    Transaction *tran)
 {
     BdrvReplaceChildState *s = g_new(BdrvReplaceChildState, 1);
     *s = (BdrvReplaceChildState) {
@@ -2760,6 +2767,14 @@ static TransactionActionDrv bdrv_attach_child_common_drv = {
 
 /*
  * Common part of attaching bdrv child to bs or to blk or to job
+ *
+ * Resulting new child is returned through @child.
+ * At start *@child must be NULL.
+ * @child is saved to a new entry of @tran, so that *@child could be reverted to
+ * NULL on abort(). So referenced variable must live at least until transaction
+ * end.
+ *
+ * Function doesn't update permissions, caller is responsible for this.
  */
 static int bdrv_attach_child_common(BlockDriverState *child_bs,
                                     const char *child_name,
@@ -2775,6 +2790,7 @@ static int bdrv_attach_child_common(BlockDriverState *child_bs,
 
     assert(child);
     assert(*child == NULL);
+    assert(child_class->get_parent_desc);
 
     new_child = g_new(BdrvChild, 1);
     *new_child = (BdrvChild) {
@@ -2834,6 +2850,12 @@ static int bdrv_attach_child_common(BlockDriverState *child_bs,
     return 0;
 }
 
+/*
+ * Variable referenced by @child must live at least until transaction end.
+ * (see bdrv_attach_child_common() doc for details)
+ *
+ * Function doesn't update permissions, caller is responsible for this.
+ */
 static int bdrv_attach_child_noperm(BlockDriverState *parent_bs,
                                     BlockDriverState *child_bs,
                                     const char *child_name,
@@ -2916,12 +2938,15 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
                                    child_role, perm, shared_perm, opaque,
                                    &child, tran, errp);
     if (ret < 0) {
-        bdrv_unref(child_bs);
-        return NULL;
+        goto out;
     }
 
     ret = bdrv_refresh_perms(child_bs, errp);
+
+out:
     tran_finalize(tran, ret);
+    /* child is unset on failure by bdrv_attach_child_common_abort() */
+    assert((ret < 0) == !child);
 
     bdrv_unref(child_bs);
     return child;
@@ -2962,6 +2987,8 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
 
 out:
     tran_finalize(tran, ret);
+    /* child is unset on failure by bdrv_attach_child_common_abort() */
+    assert((ret < 0) == !child);
 
     bdrv_unref(child_bs);
 
@@ -3093,54 +3120,104 @@ static BdrvChildRole bdrv_backing_role(BlockDriverState *bs)
 }
 
 /*
- * Sets the bs->backing link of a BDS. A new reference is created; callers
- * which don't need their own reference any more must call bdrv_unref().
+ * Sets the bs->backing or bs->file link of a BDS. A new reference is created;
+ * callers which don't need their own reference any more must call bdrv_unref().
+ *
+ * Function doesn't update permissions, caller is responsible for this.
  */
-static int bdrv_set_backing_noperm(BlockDriverState *bs,
-                                   BlockDriverState *backing_hd,
-                                   Transaction *tran, Error **errp)
+static int bdrv_set_file_or_backing_noperm(BlockDriverState *parent_bs,
+                                           BlockDriverState *child_bs,
+                                           bool is_backing,
+                                           Transaction *tran, Error **errp)
 {
     int ret = 0;
-    bool update_inherits_from = bdrv_chain_contains(bs, backing_hd) &&
-        bdrv_inherits_from_recursive(backing_hd, bs);
+    bool update_inherits_from =
+        bdrv_inherits_from_recursive(child_bs, parent_bs);
+    BdrvChild *child = is_backing ? parent_bs->backing : parent_bs->file;
+    BdrvChildRole role;
+
+    if (!parent_bs->drv) {
+        /*
+         * Node without drv is an object without a class :/. TODO: finally fix
+         * qcow2 driver to never clear bs->drv and implement format corruption
+         * handling in other way.
+         */
+        error_setg(errp, "Node corrupted");
+        return -EINVAL;
+    }
 
-    if (bdrv_is_backing_chain_frozen(bs, child_bs(bs->backing), errp)) {
+    if (child && child->frozen) {
+        error_setg(errp, "Cannot change frozen '%s' link from '%s' to '%s'",
+                   child->name, parent_bs->node_name, child->bs->node_name);
         return -EPERM;
     }
 
-    if (bs->backing) {
-        /* Cannot be frozen, we checked that above */
-        bdrv_unset_inherits_from(bs, bs->backing, tran);
-        bdrv_remove_filter_or_cow_child(bs, tran);
+    if (is_backing && !parent_bs->drv->is_filter &&
+        !parent_bs->drv->supports_backing)
+    {
+        error_setg(errp, "Driver '%s' of node '%s' does not support backing "
+                   "files", parent_bs->drv->format_name, parent_bs->node_name);
+        return -EINVAL;
     }
 
-    if (!backing_hd) {
+    if (parent_bs->drv->is_filter) {
+        role = BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY;
+    } else if (is_backing) {
+        role = BDRV_CHILD_COW;
+    } else {
+        /*
+         * We only can use same role as it is in existing child. We don't have
+         * infrastructure to determine role of file child in generic way
+         */
+        if (!child) {
+            error_setg(errp, "Cannot set file child to format node without "
+                       "file child");
+            return -EINVAL;
+        }
+        role = child->role;
+    }
+
+    if (child) {
+        bdrv_unset_inherits_from(parent_bs, child, tran);
+        bdrv_remove_file_or_backing_child(parent_bs, child, tran);
+    }
+
+    if (!child_bs) {
         goto out;
     }
 
-    ret = bdrv_attach_child_noperm(bs, backing_hd, "backing",
-                                   &child_of_bds, bdrv_backing_role(bs),
-                                   &bs->backing, tran, errp);
+    ret = bdrv_attach_child_noperm(parent_bs, child_bs,
+                                   is_backing ? "backing" : "file",
+                                   &child_of_bds, role,
+                                   is_backing ? &parent_bs->backing :
+                                                &parent_bs->file,
+                                   tran, errp);
     if (ret < 0) {
         return ret;
     }
 
 
     /*
-     * If backing_hd was already part of bs's backing chain, and
-     * inherits_from pointed recursively to bs then let's update it to
+     * If inherits_from pointed recursively to bs then let's update it to
      * point directly to bs (else it will become NULL).
      */
     if (update_inherits_from) {
-        bdrv_set_inherits_from(backing_hd, bs, tran);
+        bdrv_set_inherits_from(child_bs, parent_bs, tran);
     }
 
 out:
-    bdrv_refresh_limits(bs, tran, NULL);
+    bdrv_refresh_limits(parent_bs, tran, NULL);
 
     return 0;
 }
 
+static int bdrv_set_backing_noperm(BlockDriverState *bs,
+                                   BlockDriverState *backing_hd,
+                                   Transaction *tran, Error **errp)
+{
+    return bdrv_set_file_or_backing_noperm(bs, backing_hd, true, tran, errp);
+}
+
 int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
                         Error **errp)
 {
@@ -4018,6 +4095,19 @@ BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
                                    NULL, 0, keep_old_opts);
 }
 
+void bdrv_reopen_queue_free(BlockReopenQueue *bs_queue)
+{
+    if (bs_queue) {
+        BlockReopenQueueEntry *bs_entry, *next;
+        QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
+            qobject_unref(bs_entry->state.explicit_options);
+            qobject_unref(bs_entry->state.options);
+            g_free(bs_entry);
+        }
+        g_free(bs_queue);
+    }
+}
+
 /*
  * Reopen multiple BlockDriverStates atomically & transactionally.
  *
@@ -4034,28 +4124,38 @@ BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
  *
  * All affected nodes must be drained between bdrv_reopen_queue() and
  * bdrv_reopen_multiple().
+ *
+ * To be called from the main thread, with all other AioContexts unlocked.
  */
 int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
 {
     int ret = -1;
     BlockReopenQueueEntry *bs_entry, *next;
+    AioContext *ctx;
     Transaction *tran = tran_new();
     g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
 
+    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
     assert(bs_queue != NULL);
 
     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
+        ctx = bdrv_get_aio_context(bs_entry->state.bs);
+        aio_context_acquire(ctx);
         ret = bdrv_flush(bs_entry->state.bs);
+        aio_context_release(ctx);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Error flushing drive");
-            goto cleanup;
+            goto abort;
         }
     }
 
     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
         assert(bs_entry->state.bs->quiesce_counter > 0);
+        ctx = bdrv_get_aio_context(bs_entry->state.bs);
+        aio_context_acquire(ctx);
         ret = bdrv_reopen_prepare(&bs_entry->state, bs_queue, tran, errp);
+        aio_context_release(ctx);
         if (ret < 0) {
             goto abort;
         }
@@ -4071,6 +4171,10 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
             refresh_list = bdrv_topological_dfs(refresh_list, found,
                                                 state->old_backing_bs);
         }
+        if (state->old_file_bs) {
+            refresh_list = bdrv_topological_dfs(refresh_list, found,
+                                                state->old_file_bs);
+        }
     }
 
     /*
@@ -4094,7 +4198,10 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
      * to first element.
      */
     QTAILQ_FOREACH_REVERSE(bs_entry, bs_queue, entry) {
+        ctx = bdrv_get_aio_context(bs_entry->state.bs);
+        aio_context_acquire(ctx);
         bdrv_reopen_commit(&bs_entry->state);
+        aio_context_release(ctx);
     }
 
     tran_commit(tran);
@@ -4103,7 +4210,10 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
         BlockDriverState *bs = bs_entry->state.bs;
 
         if (bs->drv->bdrv_reopen_commit_post) {
+            ctx = bdrv_get_aio_context(bs);
+            aio_context_acquire(ctx);
             bs->drv->bdrv_reopen_commit_post(&bs_entry->state);
+            aio_context_release(ctx);
         }
     }
 
@@ -4114,59 +4224,50 @@ abort:
     tran_abort(tran);
     QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
         if (bs_entry->prepared) {
+            ctx = bdrv_get_aio_context(bs_entry->state.bs);
+            aio_context_acquire(ctx);
             bdrv_reopen_abort(&bs_entry->state);
+            aio_context_release(ctx);
         }
-        qobject_unref(bs_entry->state.explicit_options);
-        qobject_unref(bs_entry->state.options);
     }
 
 cleanup:
-    QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
-        g_free(bs_entry);
-    }
-    g_free(bs_queue);
+    bdrv_reopen_queue_free(bs_queue);
 
     return ret;
 }
 
-int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only,
-                              Error **errp)
+int bdrv_reopen(BlockDriverState *bs, QDict *opts, bool keep_old_opts,
+                Error **errp)
 {
-    int ret;
+    AioContext *ctx = bdrv_get_aio_context(bs);
     BlockReopenQueue *queue;
-    QDict *opts = qdict_new();
-
-    qdict_put_bool(opts, BDRV_OPT_READ_ONLY, read_only);
+    int ret;
 
     bdrv_subtree_drained_begin(bs);
-    queue = bdrv_reopen_queue(NULL, bs, opts, true);
+    if (ctx != qemu_get_aio_context()) {
+        aio_context_release(ctx);
+    }
+
+    queue = bdrv_reopen_queue(NULL, bs, opts, keep_old_opts);
     ret = bdrv_reopen_multiple(queue, errp);
+
+    if (ctx != qemu_get_aio_context()) {
+        aio_context_acquire(ctx);
+    }
     bdrv_subtree_drained_end(bs);
 
     return ret;
 }
 
-static bool bdrv_reopen_can_attach(BlockDriverState *parent,
-                                   BdrvChild *child,
-                                   BlockDriverState *new_child,
-                                   Error **errp)
+int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only,
+                              Error **errp)
 {
-    AioContext *parent_ctx = bdrv_get_aio_context(parent);
-    AioContext *child_ctx = bdrv_get_aio_context(new_child);
-    GSList *ignore;
-    bool ret;
+    QDict *opts = qdict_new();
 
-    ignore = g_slist_prepend(NULL, child);
-    ret = bdrv_can_set_aio_context(new_child, parent_ctx, &ignore, NULL);
-    g_slist_free(ignore);
-    if (ret) {
-        return ret;
-    }
+    qdict_put_bool(opts, BDRV_OPT_READ_ONLY, read_only);
 
-    ignore = g_slist_prepend(NULL, child);
-    ret = bdrv_can_set_aio_context(parent, child_ctx, &ignore, errp);
-    g_slist_free(ignore);
-    return ret;
+    return bdrv_reopen(bs, opts, true, errp);
 }
 
 /*
@@ -4186,115 +4287,81 @@ static bool bdrv_reopen_can_attach(BlockDriverState *parent,
  *
  * Return 0 on success, otherwise return < 0 and set @errp.
  */
-static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state,
-                                     Transaction *set_backings_tran,
-                                     Error **errp)
+static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
+                                             bool is_backing, Transaction *tran,
+                                             Error **errp)
 {
     BlockDriverState *bs = reopen_state->bs;
-    BlockDriverState *overlay_bs, *below_bs, *new_backing_bs;
+    BlockDriverState *new_child_bs;
+    BlockDriverState *old_child_bs = is_backing ? child_bs(bs->backing) :
+                                                  child_bs(bs->file);
+    const char *child_name = is_backing ? "backing" : "file";
     QObject *value;
     const char *str;
 
-    value = qdict_get(reopen_state->options, "backing");
+    value = qdict_get(reopen_state->options, child_name);
     if (value == NULL) {
         return 0;
     }
 
     switch (qobject_type(value)) {
     case QTYPE_QNULL:
-        new_backing_bs = NULL;
+        assert(is_backing); /* The 'file' option does not allow a null value */
+        new_child_bs = NULL;
         break;
     case QTYPE_QSTRING:
         str = qstring_get_str(qobject_to(QString, value));
-        new_backing_bs = bdrv_lookup_bs(NULL, str, errp);
-        if (new_backing_bs == NULL) {
+        new_child_bs = bdrv_lookup_bs(NULL, str, errp);
+        if (new_child_bs == NULL) {
             return -EINVAL;
-        } else if (bdrv_recurse_has_child(new_backing_bs, bs)) {
-            error_setg(errp, "Making '%s' a backing file of '%s' "
-                       "would create a cycle", str, bs->node_name);
+        } else if (bdrv_recurse_has_child(new_child_bs, bs)) {
+            error_setg(errp, "Making '%s' a %s child of '%s' would create a "
+                       "cycle", str, child_name, bs->node_name);
             return -EINVAL;
         }
         break;
     default:
-        /* 'backing' does not allow any other data type */
+        /*
+         * The options QDict has been flattened, so 'backing' and 'file'
+         * do not allow any other data type here.
+         */
         g_assert_not_reached();
     }
 
-    /*
-     * Check AioContext compatibility so that the bdrv_set_backing_hd() call in
-     * bdrv_reopen_commit() won't fail.
-     */
-    if (new_backing_bs) {
-        if (!bdrv_reopen_can_attach(bs, bs->backing, new_backing_bs, errp)) {
-            return -EINVAL;
-        }
+    if (old_child_bs == new_child_bs) {
+        return 0;
     }
 
-    /*
-     * Ensure that @bs can really handle backing files, because we are
-     * about to give it one (or swap the existing one)
-     */
-    if (bs->drv->is_filter) {
-        /* Filters always have a file or a backing child */
-        if (!bs->backing) {
-            error_setg(errp, "'%s' is a %s filter node that does not support a "
-                       "backing child", bs->node_name, bs->drv->format_name);
-            return -EINVAL;
+    if (old_child_bs) {
+        if (bdrv_skip_implicit_filters(old_child_bs) == new_child_bs) {
+            return 0;
         }
-    } else if (!bs->drv->supports_backing) {
-        error_setg(errp, "Driver '%s' of node '%s' does not support backing "
-                   "files", bs->drv->format_name, bs->node_name);
-        return -EINVAL;
-    }
 
-    /*
-     * Find the "actual" backing file by skipping all links that point
-     * to an implicit node, if any (e.g. a commit filter node).
-     * We cannot use any of the bdrv_skip_*() functions here because
-     * those return the first explicit node, while we are looking for
-     * its overlay here.
-     */
-    overlay_bs = bs;
-    for (below_bs = bdrv_filter_or_cow_bs(overlay_bs);
-         below_bs && below_bs->implicit;
-         below_bs = bdrv_filter_or_cow_bs(overlay_bs))
-    {
-        overlay_bs = below_bs;
-    }
-
-    /* If we want to replace the backing file we need some extra checks */
-    if (new_backing_bs != bdrv_filter_or_cow_bs(overlay_bs)) {
-        int ret;
-
-        /* Check for implicit nodes between bs and its backing file */
-        if (bs != overlay_bs) {
-            error_setg(errp, "Cannot change backing link if '%s' has "
-                       "an implicit backing file", bs->node_name);
+        if (old_child_bs->implicit) {
+            error_setg(errp, "Cannot replace implicit %s child of %s",
+                       child_name, bs->node_name);
             return -EPERM;
         }
+    }
+
+    if (bs->drv->is_filter && !old_child_bs) {
         /*
-         * Check if the backing link that we want to replace is frozen.
-         * Note that
-         * bdrv_filter_or_cow_child(overlay_bs) == overlay_bs->backing,
-         * because we know that overlay_bs == bs, and that @bs
-         * either is a filter that uses ->backing or a COW format BDS
-         * with bs->drv->supports_backing == true.
+         * Filters always have a file or a backing child, so we are trying to
+         * change wrong child
          */
-        if (bdrv_is_backing_chain_frozen(overlay_bs,
-                                         child_bs(overlay_bs->backing), errp))
-        {
-            return -EPERM;
-        }
-        reopen_state->replace_backing_bs = true;
-        reopen_state->old_backing_bs = bs->backing ? bs->backing->bs : NULL;
-        ret = bdrv_set_backing_noperm(bs, new_backing_bs, set_backings_tran,
-                                      errp);
-        if (ret < 0) {
-            return ret;
-        }
+        error_setg(errp, "'%s' is a %s filter node that does not support a "
+                   "%s child", bs->node_name, bs->drv->format_name, child_name);
+        return -EINVAL;
     }
 
-    return 0;
+    if (is_backing) {
+        reopen_state->old_backing_bs = old_child_bs;
+    } else {
+        reopen_state->old_file_bs = old_child_bs;
+    }
+
+    return bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing,
+                                           tran, errp);
 }
 
 /*
@@ -4316,7 +4383,7 @@ static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state,
  */
 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
                                BlockReopenQueue *queue,
-                               Transaction *set_backings_tran, Error **errp)
+                               Transaction *change_child_tran, Error **errp)
 {
     int ret = -1;
     int old_flags;
@@ -4436,12 +4503,21 @@ static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
      * either a reference to an existing node (using its node name)
      * or NULL to simply detach the current backing file.
      */
-    ret = bdrv_reopen_parse_backing(reopen_state, set_backings_tran, errp);
+    ret = bdrv_reopen_parse_file_or_backing(reopen_state, true,
+                                            change_child_tran, errp);
     if (ret < 0) {
         goto error;
     }
     qdict_del(reopen_state->options, "backing");
 
+    /* Allow changing the 'file' option. In this case NULL is not allowed */
+    ret = bdrv_reopen_parse_file_or_backing(reopen_state, false,
+                                            change_child_tran, errp);
+    if (ret < 0) {
+        goto error;
+    }
+    qdict_del(reopen_state->options, "file");
+
     /* 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) */
@@ -4540,24 +4616,24 @@ static void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     /* set BDS specific flags now */
     qobject_unref(bs->explicit_options);
     qobject_unref(bs->options);
+    qobject_ref(reopen_state->explicit_options);
+    qobject_ref(reopen_state->options);
 
     bs->explicit_options   = reopen_state->explicit_options;
     bs->options            = reopen_state->options;
     bs->open_flags         = reopen_state->flags;
-    bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
     bs->detect_zeroes      = reopen_state->detect_zeroes;
 
-    if (reopen_state->replace_backing_bs) {
-        qdict_del(bs->explicit_options, "backing");
-        qdict_del(bs->options, "backing");
-    }
-
     /* Remove child references from bs->options and bs->explicit_options.
      * Child options were already removed in bdrv_reopen_queue_child() */
     QLIST_FOREACH(child, &bs->children, next) {
         qdict_del(bs->explicit_options, child->name);
         qdict_del(bs->options, child->name);
     }
+    /* backing is probably removed, so it's not handled by previous loop */
+    qdict_del(bs->explicit_options, "backing");
+    qdict_del(bs->options, "backing");
+
     bdrv_refresh_limits(bs, NULL, NULL);
 }
 
@@ -4749,7 +4825,7 @@ static void bdrv_remove_filter_or_cow_child_abort(void *opaque)
     }
 
     /*
-     * We don't have to restore child->bs here to undo bdrv_replace_child()
+     * We don't have to restore child->bs here to undo bdrv_replace_child_tran()
      * because that function is transactionable and it registered own completion
      * entries in @tran, so .abort() for bdrv_replace_child_safe() will be
      * called automatically.
@@ -4770,22 +4846,23 @@ static TransactionActionDrv bdrv_remove_filter_or_cow_child_drv = {
 };
 
 /*
- * A function to remove backing-chain child of @bs if exists: cow child for
- * format nodes (always .backing) and filter child for filters (may be .file or
- * .backing)
+ * A function to remove backing or file child of @bs.
+ * Function doesn't update permissions, caller is responsible for this.
  */
-static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
-                                            Transaction *tran)
+static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
+                                              BdrvChild *child,
+                                              Transaction *tran)
 {
     BdrvRemoveFilterOrCowChild *s;
-    BdrvChild *child = bdrv_filter_or_cow_child(bs);
+
+    assert(child == bs->backing || child == bs->file);
 
     if (!child) {
         return;
     }
 
     if (child->bs) {
-        bdrv_replace_child(child, NULL, tran);
+        bdrv_replace_child_tran(child, NULL, tran);
     }
 
     s = g_new(BdrvRemoveFilterOrCowChild, 1);
@@ -4803,6 +4880,17 @@ static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
     }
 }
 
+/*
+ * A function to remove backing-chain child of @bs if exists: cow child for
+ * format nodes (always .backing) and filter child for filters (may be .file or
+ * .backing)
+ */
+static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
+                                            Transaction *tran)
+{
+    bdrv_remove_file_or_backing_child(bs, bdrv_filter_or_cow_child(bs), tran);
+}
+
 static int bdrv_replace_node_noperm(BlockDriverState *from,
                                     BlockDriverState *to,
                                     bool auto_skip, Transaction *tran,
@@ -4825,7 +4913,7 @@ static int bdrv_replace_node_noperm(BlockDriverState *from,
                        c->name, from->node_name);
             return -EPERM;
         }
-        bdrv_replace_child(c, to, tran);
+        bdrv_replace_child_tran(c, to, tran);
     }
 
     return 0;
@@ -4849,7 +4937,7 @@ static int bdrv_replace_node_common(BlockDriverState *from,
     Transaction *tran = tran_new();
     g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
-    BlockDriverState *to_cow_parent;
+    BlockDriverState *to_cow_parent = NULL;
     int ret;
 
     if (detach_subchain) {
@@ -5031,7 +5119,7 @@ int coroutine_fn bdrv_co_check(BlockDriverState *bs,
  * -ENOTSUP - format driver doesn't support changing the backing file
  */
 int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
-                             const char *backing_fmt, bool warn)
+                             const char *backing_fmt, bool require)
 {
     BlockDriver *drv = bs->drv;
     int ret;
@@ -5045,10 +5133,8 @@ int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
         return -EINVAL;
     }
 
-    if (warn && backing_file && !backing_fmt) {
-        warn_report("Deprecated use of backing file without explicit "
-                    "backing format, use of this image requires "
-                    "potentially unsafe format probing");
+    if (require && backing_file && !backing_fmt) {
+        return -EINVAL;
     }
 
     if (drv->bdrv_change_backing_file != NULL) {
@@ -6076,6 +6162,9 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
 
 void bdrv_init(void)
 {
+#ifdef CONFIG_BDRV_WHITELIST_TOOLS
+    use_bdrv_whitelist = 1;
+#endif
     module_call_init(MODULE_INIT_BLOCK);
 }
 
@@ -6536,9 +6625,13 @@ void bdrv_img_create(const char *filename, const char *fmt,
         }
         assert(full_backing);
 
-        /* backing files always opened read-only */
+        /*
+         * No need to do I/O here, which allows us to open encrypted
+         * backing images without needing the secret
+         */
         back_flags = flags;
         back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
+        back_flags |= BDRV_O_NO_IO;
 
         backing_options = qdict_new();
         if (backing_fmt) {
@@ -6554,24 +6647,11 @@ void bdrv_img_create(const char *filename, const char *fmt,
             goto out;
         } else {
             if (!backing_fmt) {
-                warn_report("Deprecated use of backing file without explicit "
-                            "backing format (detected format of %s)",
-                            bs->drv->format_name);
-                if (bs->drv != &bdrv_raw) {
-                    /*
-                     * A probe of raw deserves the most attention:
-                     * leaving the backing format out of the image
-                     * will ensure bs->probed is set (ensuring we
-                     * don't accidentally commit into the backing
-                     * file), and allow more spots to warn the users
-                     * to fix their toolchain when opening this image
-                     * later.  For other images, we can safely record
-                     * the format that we probed.
-                     */
-                    backing_fmt = bs->drv->format_name;
-                    qemu_opt_set(opts, BLOCK_OPT_BACKING_FMT, backing_fmt,
-                                 NULL);
-                }
+                error_setg(&local_err,
+                           "Backing file specified without backing format");
+                error_append_hint(&local_err, "Detected format of %s.",
+                                  bs->drv->format_name);
+                goto out;
             }
             if (size == -1) {
                 /* Opened BS, have no size */
@@ -6588,9 +6668,9 @@ void bdrv_img_create(const char *filename, const char *fmt,
         }
         /* (backing_file && !(flags & BDRV_O_NO_BACKING)) */
     } else if (backing_file && !backing_fmt) {
-        warn_report("Deprecated use of unopened backing file without "
-                    "explicit backing format, use of this image requires "
-                    "potentially unsafe format probing");
+        error_setg(&local_err,
+                   "Backing file specified without backing format");
+        goto out;
     }
 
     if (size == -1) {