Initial import of abandoned HQEMU version 2.5.2HEADmaster

1 files changed, 4059 insertions, 0 deletions

diff --git a/src/block.c b/src/block.c
new file mode 100644
index 0000000..3c172dd
--- /dev/null
+++ b/src/block.c
@@ -0,0 +1,4059 @@
+/*
+ * QEMU System Emulator block driver
+ *
+ * Copyright (c) 2003 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "config-host.h"
+#include "qemu-common.h"
+#include "trace.h"
+#include "block/block_int.h"
+#include "block/blockjob.h"
+#include "qemu/error-report.h"
+#include "qemu/module.h"
+#include "qapi/qmp/qerror.h"
+#include "qapi/qmp/qjson.h"
+#include "sysemu/block-backend.h"
+#include "sysemu/sysemu.h"
+#include "qemu/notify.h"
+#include "qemu/coroutine.h"
+#include "block/qapi.h"
+#include "qmp-commands.h"
+#include "qemu/timer.h"
+#include "qapi-event.h"
+#include "block/throttle-groups.h"
+
+#ifdef CONFIG_BSD
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <sys/queue.h>
+#ifndef __DragonFly__
+#include <sys/disk.h>
+#endif
+#endif
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+/**
+ * A BdrvDirtyBitmap can be in three possible states:
+ * (1) successor is NULL and disabled is false: full r/w mode
+ * (2) successor is NULL and disabled is true: read only mode ("disabled")
+ * (3) successor is set: frozen mode.
+ *     A frozen bitmap cannot be renamed, deleted, anonymized, cleared, set,
+ *     or enabled. A frozen bitmap can only abdicate() or reclaim().
+ */
+struct BdrvDirtyBitmap {
+    HBitmap *bitmap;            /* Dirty sector bitmap implementation */
+    BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
+    char *name;                 /* Optional non-empty unique ID */
+    int64_t size;               /* Size of the bitmap (Number of sectors) */
+    bool disabled;              /* Bitmap is read-only */
+    QLIST_ENTRY(BdrvDirtyBitmap) list;
+};
+
+#define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
+
+struct BdrvStates bdrv_states = QTAILQ_HEAD_INITIALIZER(bdrv_states);
+
+static QTAILQ_HEAD(, BlockDriverState) graph_bdrv_states =
+    QTAILQ_HEAD_INITIALIZER(graph_bdrv_states);
+
+static QLIST_HEAD(, BlockDriver) bdrv_drivers =
+    QLIST_HEAD_INITIALIZER(bdrv_drivers);
+
+static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
+                             const char *reference, QDict *options, int flags,
+                             BlockDriverState *parent,
+                             const BdrvChildRole *child_role, Error **errp);
+
+static void bdrv_dirty_bitmap_truncate(BlockDriverState *bs);
+/* If non-zero, use only whitelisted block drivers */
+static int use_bdrv_whitelist;
+
+#ifdef _WIN32
+static int is_windows_drive_prefix(const char *filename)
+{
+    return (((filename[0] >= 'a' && filename[0] <= 'z') ||
+             (filename[0] >= 'A' && filename[0] <= 'Z')) &&
+            filename[1] == ':');
+}
+
+int is_windows_drive(const char *filename)
+{
+    if (is_windows_drive_prefix(filename) &&
+        filename[2] == '\0')
+        return 1;
+    if (strstart(filename, "\\\\.\\", NULL) ||
+        strstart(filename, "//./", NULL))
+        return 1;
+    return 0;
+}
+#endif
+
+size_t bdrv_opt_mem_align(BlockDriverState *bs)
+{
+    if (!bs || !bs->drv) {
+        /* page size or 4k (hdd sector size) should be on the safe side */
+        return MAX(4096, getpagesize());
+    }
+
+    return bs->bl.opt_mem_alignment;
+}
+
+size_t bdrv_min_mem_align(BlockDriverState *bs)
+{
+    if (!bs || !bs->drv) {
+        /* page size or 4k (hdd sector size) should be on the safe side */
+        return MAX(4096, getpagesize());
+    }
+
+    return bs->bl.min_mem_alignment;
+}
+
+/* check if the path starts with "<protocol>:" */
+int path_has_protocol(const char *path)
+{
+    const char *p;
+
+#ifdef _WIN32
+    if (is_windows_drive(path) ||
+        is_windows_drive_prefix(path)) {
+        return 0;
+    }
+    p = path + strcspn(path, ":/\\");
+#else
+    p = path + strcspn(path, ":/");
+#endif
+
+    return *p == ':';
+}
+
+int path_is_absolute(const char *path)
+{
+#ifdef _WIN32
+    /* specific case for names like: "\\.\d:" */
+    if (is_windows_drive(path) || is_windows_drive_prefix(path)) {
+        return 1;
+    }
+    return (*path == '/' || *path == '\\');
+#else
+    return (*path == '/');
+#endif
+}
+
+/* if filename is absolute, just copy it to dest. Otherwise, build a
+   path to it by considering it is relative to base_path. URL are
+   supported. */
+void path_combine(char *dest, int dest_size,
+                  const char *base_path,
+                  const char *filename)
+{
+    const char *p, *p1;
+    int len;
+
+    if (dest_size <= 0)
+        return;
+    if (path_is_absolute(filename)) {
+        pstrcpy(dest, dest_size, filename);
+    } else {
+        p = strchr(base_path, ':');
+        if (p)
+            p++;
+        else
+            p = base_path;
+        p1 = strrchr(base_path, '/');
+#ifdef _WIN32
+        {
+            const char *p2;
+            p2 = strrchr(base_path, '\\');
+            if (!p1 || p2 > p1)
+                p1 = p2;
+        }
+#endif
+        if (p1)
+            p1++;
+        else
+            p1 = base_path;
+        if (p1 > p)
+            p = p1;
+        len = p - base_path;
+        if (len > dest_size - 1)
+            len = dest_size - 1;
+        memcpy(dest, base_path, len);
+        dest[len] = '\0';
+        pstrcat(dest, dest_size, filename);
+    }
+}
+
+void bdrv_get_full_backing_filename_from_filename(const char *backed,
+                                                  const char *backing,
+                                                  char *dest, size_t sz,
+                                                  Error **errp)
+{
+    if (backing[0] == '\0' || path_has_protocol(backing) ||
+        path_is_absolute(backing))
+    {
+        pstrcpy(dest, sz, backing);
+    } else if (backed[0] == '\0' || strstart(backed, "json:", NULL)) {
+        error_setg(errp, "Cannot use relative backing file names for '%s'",
+                   backed);
+    } else {
+        path_combine(dest, sz, backed, backing);
+    }
+}
+
+void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz,
+                                    Error **errp)
+{
+    char *backed = bs->exact_filename[0] ? bs->exact_filename : bs->filename;
+
+    bdrv_get_full_backing_filename_from_filename(backed, bs->backing_file,
+                                                 dest, sz, errp);
+}
+
+void bdrv_register(BlockDriver *bdrv)
+{
+    bdrv_setup_io_funcs(bdrv);
+
+    QLIST_INSERT_HEAD(&bdrv_drivers, bdrv, list);
+}
+
+BlockDriverState *bdrv_new_root(void)
+{
+    BlockDriverState *bs = bdrv_new();
+
+    QTAILQ_INSERT_TAIL(&bdrv_states, bs, device_list);
+    return bs;
+}
+
+BlockDriverState *bdrv_new(void)
+{
+    BlockDriverState *bs;
+    int i;
+
+    bs = g_new0(BlockDriverState, 1);
+    QLIST_INIT(&bs->dirty_bitmaps);
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        QLIST_INIT(&bs->op_blockers[i]);
+    }
+    notifier_list_init(&bs->close_notifiers);
+    notifier_with_return_list_init(&bs->before_write_notifiers);
+    qemu_co_queue_init(&bs->throttled_reqs[0]);
+    qemu_co_queue_init(&bs->throttled_reqs[1]);
+    bs->refcnt = 1;
+    bs->aio_context = qemu_get_aio_context();
+
+    return bs;
+}
+
+void bdrv_add_close_notifier(BlockDriverState *bs, Notifier *notify)
+{
+    notifier_list_add(&bs->close_notifiers, notify);
+}
+
+BlockDriver *bdrv_find_format(const char *format_name)
+{
+    BlockDriver *drv1;
+    QLIST_FOREACH(drv1, &bdrv_drivers, list) {
+        if (!strcmp(drv1->format_name, format_name)) {
+            return drv1;
+        }
+    }
+    return NULL;
+}
+
+static int bdrv_is_whitelisted(BlockDriver *drv, bool read_only)
+{
+    static const char *whitelist_rw[] = {
+        CONFIG_BDRV_RW_WHITELIST
+    };
+    static const char *whitelist_ro[] = {
+        CONFIG_BDRV_RO_WHITELIST
+    };
+    const char **p;
+
+    if (!whitelist_rw[0] && !whitelist_ro[0]) {
+        return 1;               /* no whitelist, anything goes */
+    }
+
+    for (p = whitelist_rw; *p; p++) {
+        if (!strcmp(drv->format_name, *p)) {
+            return 1;
+        }
+    }
+    if (read_only) {
+        for (p = whitelist_ro; *p; p++) {
+            if (!strcmp(drv->format_name, *p)) {
+                return 1;
+            }
+        }
+    }
+    return 0;
+}
+
+typedef struct CreateCo {
+    BlockDriver *drv;
+    char *filename;
+    QemuOpts *opts;
+    int ret;
+    Error *err;
+} CreateCo;
+
+static void coroutine_fn bdrv_create_co_entry(void *opaque)
+{
+    Error *local_err = NULL;
+    int ret;
+
+    CreateCo *cco = opaque;
+    assert(cco->drv);
+
+    ret = cco->drv->bdrv_create(cco->filename, cco->opts, &local_err);
+    if (local_err) {
+        error_propagate(&cco->err, local_err);
+    }
+    cco->ret = ret;
+}
+
+int bdrv_create(BlockDriver *drv, const char* filename,
+                QemuOpts *opts, Error **errp)
+{
+    int ret;
+
+    Coroutine *co;
+    CreateCo cco = {
+        .drv = drv,
+        .filename = g_strdup(filename),
+        .opts = opts,
+        .ret = NOT_DONE,
+        .err = NULL,
+    };
+
+    if (!drv->bdrv_create) {
+        error_setg(errp, "Driver '%s' does not support image creation", drv->format_name);
+        ret = -ENOTSUP;
+        goto out;
+    }
+
+    if (qemu_in_coroutine()) {
+        /* Fast-path if already in coroutine context */
+        bdrv_create_co_entry(&cco);
+    } else {
+        co = qemu_coroutine_create(bdrv_create_co_entry);
+        qemu_coroutine_enter(co, &cco);
+        while (cco.ret == NOT_DONE) {
+            aio_poll(qemu_get_aio_context(), true);
+        }
+    }
+
+    ret = cco.ret;
+    if (ret < 0) {
+        if (cco.err) {
+            error_propagate(errp, cco.err);
+        } else {
+            error_setg_errno(errp, -ret, "Could not create image");
+        }
+    }
+
+out:
+    g_free(cco.filename);
+    return ret;
+}
+
+int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp)
+{
+    BlockDriver *drv;
+    Error *local_err = NULL;
+    int ret;
+
+    drv = bdrv_find_protocol(filename, true, errp);
+    if (drv == NULL) {
+        return -ENOENT;
+    }
+
+    ret = bdrv_create(drv, filename, opts, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
+    return ret;
+}
+
+/**
+ * Try to get @bs's logical and physical block size.
+ * On success, store them in @bsz struct and return 0.
+ * On failure return -errno.
+ * @bs must not be empty.
+ */
+int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (drv && drv->bdrv_probe_blocksizes) {
+        return drv->bdrv_probe_blocksizes(bs, bsz);
+    }
+
+    return -ENOTSUP;
+}
+
+/**
+ * Try to get @bs's geometry (cyls, heads, sectors).
+ * On success, store them in @geo struct and return 0.
+ * On failure return -errno.
+ * @bs must not be empty.
+ */
+int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (drv && drv->bdrv_probe_geometry) {
+        return drv->bdrv_probe_geometry(bs, geo);
+    }
+
+    return -ENOTSUP;
+}
+
+/*
+ * Create a uniquely-named empty temporary file.
+ * Return 0 upon success, otherwise a negative errno value.
+ */
+int get_tmp_filename(char *filename, int size)
+{
+#ifdef _WIN32
+    char temp_dir[MAX_PATH];
+    /* GetTempFileName requires that its output buffer (4th param)
+       have length MAX_PATH or greater.  */
+    assert(size >= MAX_PATH);
+    return (GetTempPath(MAX_PATH, temp_dir)
+            && GetTempFileName(temp_dir, "qem", 0, filename)
+            ? 0 : -GetLastError());
+#else
+    int fd;
+    const char *tmpdir;
+    tmpdir = getenv("TMPDIR");
+    if (!tmpdir) {
+        tmpdir = "/var/tmp";
+    }
+    if (snprintf(filename, size, "%s/vl.XXXXXX", tmpdir) >= size) {
+        return -EOVERFLOW;
+    }
+    fd = mkstemp(filename);
+    if (fd < 0) {
+        return -errno;
+    }
+    if (close(fd) != 0) {
+        unlink(filename);
+        return -errno;
+    }
+    return 0;
+#endif
+}
+
+/*
+ * Detect host devices. By convention, /dev/cdrom[N] is always
+ * recognized as a host CDROM.
+ */
+static BlockDriver *find_hdev_driver(const char *filename)
+{
+    int score_max = 0, score;
+    BlockDriver *drv = NULL, *d;
+
+    QLIST_FOREACH(d, &bdrv_drivers, list) {
+        if (d->bdrv_probe_device) {
+            score = d->bdrv_probe_device(filename);
+            if (score > score_max) {
+                score_max = score;
+                drv = d;
+            }
+        }
+    }
+
+    return drv;
+}
+
+BlockDriver *bdrv_find_protocol(const char *filename,
+                                bool allow_protocol_prefix,
+                                Error **errp)
+{
+    BlockDriver *drv1;
+    char protocol[128];
+    int len;
+    const char *p;
+
+    /* TODO Drivers without bdrv_file_open must be specified explicitly */
+
+    /*
+     * XXX(hch): we really should not let host device detection
+     * override an explicit protocol specification, but moving this
+     * later breaks access to device names with colons in them.
+     * Thanks to the brain-dead persistent naming schemes on udev-
+     * based Linux systems those actually are quite common.
+     */
+    drv1 = find_hdev_driver(filename);
+    if (drv1) {
+        return drv1;
+    }
+
+    if (!path_has_protocol(filename) || !allow_protocol_prefix) {
+        return &bdrv_file;
+    }
+
+    p = strchr(filename, ':');
+    assert(p != NULL);
+    len = p - filename;
+    if (len > sizeof(protocol) - 1)
+        len = sizeof(protocol) - 1;
+    memcpy(protocol, filename, len);
+    protocol[len] = '\0';
+    QLIST_FOREACH(drv1, &bdrv_drivers, list) {
+        if (drv1->protocol_name &&
+            !strcmp(drv1->protocol_name, protocol)) {
+            return drv1;
+        }
+    }
+
+    error_setg(errp, "Unknown protocol '%s'", protocol);
+    return NULL;
+}
+
+/*
+ * Guess image format by probing its contents.
+ * This is not a good idea when your image is raw (CVE-2008-2004), but
+ * we do it anyway for backward compatibility.
+ *
+ * @buf         contains the image's first @buf_size bytes.
+ * @buf_size    is the buffer size in bytes (generally BLOCK_PROBE_BUF_SIZE,
+ *              but can be smaller if the image file is smaller)
+ * @filename    is its filename.
+ *
+ * For all block drivers, call the bdrv_probe() method to get its
+ * probing score.
+ * Return the first block driver with the highest probing score.
+ */
+BlockDriver *bdrv_probe_all(const uint8_t *buf, int buf_size,
+                            const char *filename)
+{
+    int score_max = 0, score;
+    BlockDriver *drv = NULL, *d;
+
+    QLIST_FOREACH(d, &bdrv_drivers, list) {
+        if (d->bdrv_probe) {
+            score = d->bdrv_probe(buf, buf_size, filename);
+            if (score > score_max) {
+                score_max = score;
+                drv = d;
+            }
+        }
+    }
+
+    return drv;
+}
+
+static int find_image_format(BlockDriverState *bs, const char *filename,
+                             BlockDriver **pdrv, Error **errp)
+{
+    BlockDriver *drv;
+    uint8_t buf[BLOCK_PROBE_BUF_SIZE];
+    int ret = 0;
+
+    /* Return the raw BlockDriver * to scsi-generic devices or empty drives */
+    if (bdrv_is_sg(bs) || !bdrv_is_inserted(bs) || bdrv_getlength(bs) == 0) {
+        *pdrv = &bdrv_raw;
+        return ret;
+    }
+
+    ret = bdrv_pread(bs, 0, buf, sizeof(buf));
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not read image for determining its "
+                         "format");
+        *pdrv = NULL;
+        return ret;
+    }
+
+    drv = bdrv_probe_all(buf, ret, filename);
+    if (!drv) {
+        error_setg(errp, "Could not determine image format: No compatible "
+                   "driver found");
+        ret = -ENOENT;
+    }
+    *pdrv = drv;
+    return ret;
+}
+
+/**
+ * Set the current 'total_sectors' value
+ * Return 0 on success, -errno on error.
+ */
+static int refresh_total_sectors(BlockDriverState *bs, int64_t hint)
+{
+    BlockDriver *drv = bs->drv;
+
+    /* Do not attempt drv->bdrv_getlength() on scsi-generic devices */
+    if (bdrv_is_sg(bs))
+        return 0;
+
+    /* query actual device if possible, otherwise just trust the hint */
+    if (drv->bdrv_getlength) {
+        int64_t length = drv->bdrv_getlength(bs);
+        if (length < 0) {
+            return length;
+        }
+        hint = DIV_ROUND_UP(length, BDRV_SECTOR_SIZE);
+    }
+
+    bs->total_sectors = hint;
+    return 0;
+}
+
+/**
+ * Set open flags for a given discard mode
+ *
+ * Return 0 on success, -1 if the discard mode was invalid.
+ */
+int bdrv_parse_discard_flags(const char *mode, int *flags)
+{
+    *flags &= ~BDRV_O_UNMAP;
+
+    if (!strcmp(mode, "off") || !strcmp(mode, "ignore")) {
+        /* do nothing */
+    } else if (!strcmp(mode, "on") || !strcmp(mode, "unmap")) {
+        *flags |= BDRV_O_UNMAP;
+    } else {
+        return -1;
+    }
+
+    return 0;
+}
+
+/**
+ * Set open flags for a given cache mode
+ *
+ * Return 0 on success, -1 if the cache mode was invalid.
+ */
+int bdrv_parse_cache_flags(const char *mode, int *flags)
+{
+    *flags &= ~BDRV_O_CACHE_MASK;
+
+    if (!strcmp(mode, "off") || !strcmp(mode, "none")) {
+        *flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB;
+    } else if (!strcmp(mode, "directsync")) {
+        *flags |= BDRV_O_NOCACHE;
+    } else if (!strcmp(mode, "writeback")) {
+        *flags |= BDRV_O_CACHE_WB;
+    } else if (!strcmp(mode, "unsafe")) {
+        *flags |= BDRV_O_CACHE_WB;
+        *flags |= BDRV_O_NO_FLUSH;
+    } else if (!strcmp(mode, "writethrough")) {
+        /* this is the default */
+    } else {
+        return -1;
+    }
+
+    return 0;
+}
+
+/*
+ * Returns the flags that a temporary snapshot should get, based on the
+ * originally requested flags (the originally requested image will have flags
+ * like a backing file)
+ */
+static int bdrv_temp_snapshot_flags(int flags)
+{
+    return (flags & ~BDRV_O_SNAPSHOT) | BDRV_O_TEMPORARY;
+}
+
+/*
+ * Returns the flags that bs->file should get if a protocol driver is expected,
+ * based on the given flags for the parent BDS
+ */
+static int bdrv_inherited_flags(int flags)
+{
+    /* Enable protocol handling, disable format probing for bs->file */
+    flags |= BDRV_O_PROTOCOL;
+
+    /* Our block drivers take care to send flushes and respect unmap policy,
+     * so we can enable both unconditionally on lower layers. */
+    flags |= BDRV_O_CACHE_WB | BDRV_O_UNMAP;
+
+    /* Clear flags that only apply to the top layer */
+    flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_COPY_ON_READ);
+
+    return flags;
+}
+
+const BdrvChildRole child_file = {
+    .inherit_flags = bdrv_inherited_flags,
+};
+
+/*
+ * Returns the flags that bs->file should get if the use of formats (and not
+ * only protocols) is permitted for it, based on the given flags for the parent
+ * BDS
+ */
+static int bdrv_inherited_fmt_flags(int parent_flags)
+{
+    int flags = child_file.inherit_flags(parent_flags);
+    return flags & ~BDRV_O_PROTOCOL;
+}
+
+const BdrvChildRole child_format = {
+    .inherit_flags = bdrv_inherited_fmt_flags,
+};
+
+/*
+ * Returns the flags that bs->backing should get, based on the given flags
+ * for the parent BDS
+ */
+static int bdrv_backing_flags(int flags)
+{
+    /* backing files always opened read-only */
+    flags &= ~(BDRV_O_RDWR | BDRV_O_COPY_ON_READ);
+
+    /* snapshot=on is handled on the top layer */
+    flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_TEMPORARY);
+
+    return flags;
+}
+
+static const BdrvChildRole child_backing = {
+    .inherit_flags = bdrv_backing_flags,
+};
+
+static int bdrv_open_flags(BlockDriverState *bs, int flags)
+{
+    int open_flags = flags | BDRV_O_CACHE_WB;
+
+    /*
+     * Clear flags that are internal to the block layer before opening the
+     * image.
+     */
+    open_flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_PROTOCOL);
+
+    /*
+     * Snapshots should be writable.
+     */
+    if (flags & BDRV_O_TEMPORARY) {
+        open_flags |= BDRV_O_RDWR;
+    }
+
+    return open_flags;
+}
+
+static void bdrv_assign_node_name(BlockDriverState *bs,
+                                  const char *node_name,
+                                  Error **errp)
+{
+    char *gen_node_name = NULL;
+
+    if (!node_name) {
+        node_name = gen_node_name = id_generate(ID_BLOCK);
+    } else if (!id_wellformed(node_name)) {
+        /*
+         * Check for empty string or invalid characters, but not if it is
+         * generated (generated names use characters not available to the user)
+         */
+        error_setg(errp, "Invalid node name");
+        return;
+    }
+
+    /* takes care of avoiding namespaces collisions */
+    if (blk_by_name(node_name)) {
+        error_setg(errp, "node-name=%s is conflicting with a device id",
+                   node_name);
+        goto out;
+    }
+
+    /* takes care of avoiding duplicates node names */
+    if (bdrv_find_node(node_name)) {
+        error_setg(errp, "Duplicate node name");
+        goto out;
+    }
+
+    /* copy node name into the bs and insert it into the graph list */
+    pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
+    QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
+out:
+    g_free(gen_node_name);
+}
+
+static QemuOptsList bdrv_runtime_opts = {
+    .name = "bdrv_common",
+    .head = QTAILQ_HEAD_INITIALIZER(bdrv_runtime_opts.head),
+    .desc = {
+        {
+            .name = "node-name",
+            .type = QEMU_OPT_STRING,
+            .help = "Node name of the block device node",
+        },
+        { /* end of list */ }
+    },
+};
+
+/*
+ * Common part for opening disk images and files
+ *
+ * Removes all processed options from *options.
+ */
+static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
+    QDict *options, int flags, BlockDriver *drv, Error **errp)
+{
+    int ret, open_flags;
+    const char *filename;
+    const char *node_name = NULL;
+    QemuOpts *opts;
+    Error *local_err = NULL;
+
+    assert(drv != NULL);
+    assert(bs->file == NULL);
+    assert(options != NULL && bs->options != options);
+
+    if (file != NULL) {
+        filename = file->bs->filename;
+    } else {
+        filename = qdict_get_try_str(options, "filename");
+    }
+
+    if (drv->bdrv_needs_filename && !filename) {
+        error_setg(errp, "The '%s' block driver requires a file name",
+                   drv->format_name);
+        return -EINVAL;
+    }
+
+    trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
+
+    opts = qemu_opts_create(&bdrv_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_opts;
+    }
+
+    node_name = qemu_opt_get(opts, "node-name");
+    bdrv_assign_node_name(bs, node_name, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail_opts;
+    }
+
+    bs->request_alignment = 512;
+    bs->zero_beyond_eof = true;
+    open_flags = bdrv_open_flags(bs, flags);
+    bs->read_only = !(open_flags & BDRV_O_RDWR);
+
+    if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, bs->read_only)) {
+        error_setg(errp,
+                   !bs->read_only && bdrv_is_whitelisted(drv, true)
+                        ? "Driver '%s' can only be used for read-only devices"
+                        : "Driver '%s' is not whitelisted",
+                   drv->format_name);
+        ret = -ENOTSUP;
+        goto fail_opts;
+    }
+
+    assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */
+    if (flags & BDRV_O_COPY_ON_READ) {
+        if (!bs->read_only) {
+            bdrv_enable_copy_on_read(bs);
+        } else {
+            error_setg(errp, "Can't use copy-on-read on read-only device");
+            ret = -EINVAL;
+            goto fail_opts;
+        }
+    }
+
+    if (filename != NULL) {
+        pstrcpy(bs->filename, sizeof(bs->filename), filename);
+    } else {
+        bs->filename[0] = '\0';
+    }
+    pstrcpy(bs->exact_filename, sizeof(bs->exact_filename), bs->filename);
+
+    bs->drv = drv;
+    bs->opaque = g_malloc0(drv->instance_size);
+
+    bs->enable_write_cache = !!(flags & BDRV_O_CACHE_WB);
+
+    /* Open the image, either directly or using a protocol */
+    if (drv->bdrv_file_open) {
+        assert(file == NULL);
+        assert(!drv->bdrv_needs_filename || filename != NULL);
+        ret = drv->bdrv_file_open(bs, options, open_flags, &local_err);
+    } else {
+        if (file == NULL) {
+            error_setg(errp, "Can't use '%s' as a block driver for the "
+                       "protocol level", drv->format_name);
+            ret = -EINVAL;
+            goto free_and_fail;
+        }
+        bs->file = file;
+        ret = drv->bdrv_open(bs, options, open_flags, &local_err);
+    }
+
+    if (ret < 0) {
+        if (local_err) {
+            error_propagate(errp, local_err);
+        } else if (bs->filename[0]) {
+            error_setg_errno(errp, -ret, "Could not open '%s'", bs->filename);
+        } else {
+            error_setg_errno(errp, -ret, "Could not open image");
+        }
+        goto free_and_fail;
+    }
+
+    if (bs->encrypted) {
+        error_report("Encrypted images are deprecated");
+        error_printf("Support for them will be removed in a future release.\n"
+                     "You can use 'qemu-img convert' to convert your image"
+                     " to an unencrypted one.\n");
+    }
+
+    ret = refresh_total_sectors(bs, bs->total_sectors);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not refresh total sector count");
+        goto free_and_fail;
+    }
+
+    bdrv_refresh_limits(bs, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto free_and_fail;
+    }
+
+    assert(bdrv_opt_mem_align(bs) != 0);
+    assert(bdrv_min_mem_align(bs) != 0);
+    assert((bs->request_alignment != 0) || bdrv_is_sg(bs));
+
+    qemu_opts_del(opts);
+    return 0;
+
+free_and_fail:
+    bs->file = NULL;
+    g_free(bs->opaque);
+    bs->opaque = NULL;
+    bs->drv = NULL;
+fail_opts:
+    qemu_opts_del(opts);
+    return ret;
+}
+
+static QDict *parse_json_filename(const char *filename, Error **errp)
+{
+    QObject *options_obj;
+    QDict *options;
+    int ret;
+
+    ret = strstart(filename, "json:", &filename);
+    assert(ret);
+
+    options_obj = qobject_from_json(filename);
+    if (!options_obj) {
+        error_setg(errp, "Could not parse the JSON options");
+        return NULL;
+    }
+
+    if (qobject_type(options_obj) != QTYPE_QDICT) {
+        qobject_decref(options_obj);
+        error_setg(errp, "Invalid JSON object given");
+        return NULL;
+    }
+
+    options = qobject_to_qdict(options_obj);
+    qdict_flatten(options);
+
+    return options;
+}
+
+/*
+ * Fills in default options for opening images and converts the legacy
+ * filename/flags pair to option QDict entries.
+ * The BDRV_O_PROTOCOL flag in *flags will be set or cleared accordingly if a
+ * block driver has been specified explicitly.
+ */
+static int bdrv_fill_options(QDict **options, const char **pfilename,
+                             int *flags, Error **errp)
+{
+    const char *filename = *pfilename;
+    const char *drvname;
+    bool protocol = *flags & BDRV_O_PROTOCOL;
+    bool parse_filename = false;
+    BlockDriver *drv = NULL;
+    Error *local_err = NULL;
+
+    /* Parse json: pseudo-protocol */
+    if (filename && g_str_has_prefix(filename, "json:")) {
+        QDict *json_options = parse_json_filename(filename, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return -EINVAL;
+        }
+
+        /* Options given in the filename have lower priority than options
+         * specified directly */
+        qdict_join(*options, json_options, false);
+        QDECREF(json_options);
+        *pfilename = filename = NULL;
+    }
+
+    drvname = qdict_get_try_str(*options, "driver");
+    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) {
+        *flags |= BDRV_O_PROTOCOL;
+    } else {
+        *flags &= ~BDRV_O_PROTOCOL;
+    }
+
+    /* Fetch the file name from the options QDict if necessary */
+    if (protocol && filename) {
+        if (!qdict_haskey(*options, "filename")) {
+            qdict_put(*options, "filename", qstring_from_str(filename));
+            parse_filename = true;
+        } else {
+            error_setg(errp, "Can't specify 'file' and 'filename' options at "
+                             "the same time");
+            return -EINVAL;
+        }
+    }
+
+    /* Find the right block driver */
+    filename = qdict_get_try_str(*options, "filename");
+
+    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");
+            return -EINVAL;
+        }
+    }
+
+    assert(drv || !protocol);
+
+    /* Driver-specific filename parsing */
+    if (drv && drv->bdrv_parse_filename && parse_filename) {
+        drv->bdrv_parse_filename(filename, *options, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return -EINVAL;
+        }
+
+        if (!drv->bdrv_needs_filename) {
+            qdict_del(*options, "filename");
+        }
+    }
+
+    if (runstate_check(RUN_STATE_INMIGRATE)) {
+        *flags |= BDRV_O_INCOMING;
+    }
+
+    return 0;
+}
+
+static BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
+                                    BlockDriverState *child_bs,
+                                    const BdrvChildRole *child_role)
+{
+    BdrvChild *child = g_new(BdrvChild, 1);
+    *child = (BdrvChild) {
+        .bs     = child_bs,
+        .role   = child_role,
+    };
+
+    QLIST_INSERT_HEAD(&parent_bs->children, child, next);
+    QLIST_INSERT_HEAD(&child_bs->parents, child, next_parent);
+
+    return child;
+}
+
+static void bdrv_detach_child(BdrvChild *child)
+{
+    QLIST_REMOVE(child, next);
+    QLIST_REMOVE(child, next_parent);
+    g_free(child);
+}
+
+void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child)
+{
+    BlockDriverState *child_bs;
+
+    if (child == NULL) {
+        return;
+    }
+
+    if (child->bs->inherits_from == parent) {
+        child->bs->inherits_from = NULL;
+    }
+
+    child_bs = child->bs;
+    bdrv_detach_child(child);
+    bdrv_unref(child_bs);
+}
+
+/*
+ * Sets the backing file link of a BDS. A new reference is created; callers
+ * which don't need their own reference any more must call bdrv_unref().
+ */
+void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
+{
+    if (backing_hd) {
+        bdrv_ref(backing_hd);
+    }
+
+    if (bs->backing) {
+        assert(bs->backing_blocker);
+        bdrv_op_unblock_all(bs->backing->bs, bs->backing_blocker);
+        bdrv_unref_child(bs, bs->backing);
+    } else if (backing_hd) {
+        error_setg(&bs->backing_blocker,
+                   "node is used as backing hd of '%s'",
+                   bdrv_get_device_or_node_name(bs));
+    }
+
+    if (!backing_hd) {
+        error_free(bs->backing_blocker);
+        bs->backing_blocker = NULL;
+        bs->backing = NULL;
+        goto out;
+    }
+    bs->backing = bdrv_attach_child(bs, backing_hd, &child_backing);
+    bs->open_flags &= ~BDRV_O_NO_BACKING;
+    pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_hd->filename);
+    pstrcpy(bs->backing_format, sizeof(bs->backing_format),
+            backing_hd->drv ? backing_hd->drv->format_name : "");
+
+    bdrv_op_block_all(backing_hd, bs->backing_blocker);
+    /* Otherwise we won't be able to commit due to check in bdrv_commit */
+    bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_COMMIT_TARGET,
+                    bs->backing_blocker);
+out:
+    bdrv_refresh_limits(bs, NULL);
+}
+
+/*
+ * Opens the backing file for a BlockDriverState if not yet open
+ *
+ * options is a QDict of options to pass to the block drivers, or NULL for an
+ * empty set of options. The reference to the QDict is transferred to this
+ * function (even on failure), so if the caller intends to reuse the dictionary,
+ * it needs to use QINCREF() before calling bdrv_file_open.
+ */
+int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
+{
+    char *backing_filename = g_malloc0(PATH_MAX);
+    int ret = 0;
+    BlockDriverState *backing_hd;
+    Error *local_err = NULL;
+
+    if (bs->backing != NULL) {
+        QDECREF(options);
+        goto free_exit;
+    }
+
+    /* NULL means an empty set of options */
+    if (options == NULL) {
+        options = qdict_new();
+    }
+
+    bs->open_flags &= ~BDRV_O_NO_BACKING;
+    if (qdict_haskey(options, "file.filename")) {
+        backing_filename[0] = '\0';
+    } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
+        QDECREF(options);
+        goto free_exit;
+    } else {
+        bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX,
+                                       &local_err);
+        if (local_err) {
+            ret = -EINVAL;
+            error_propagate(errp, local_err);
+            QDECREF(options);
+            goto free_exit;
+        }
+    }
+
+    if (!bs->drv || !bs->drv->supports_backing) {
+        ret = -EINVAL;
+        error_setg(errp, "Driver doesn't support backing files");
+        QDECREF(options);
+        goto free_exit;
+    }
+
+    backing_hd = bdrv_new();
+
+    if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
+        qdict_put(options, "driver", qstring_from_str(bs->backing_format));
+    }
+
+    assert(bs->backing == NULL);
+    ret = bdrv_open_inherit(&backing_hd,
+                            *backing_filename ? backing_filename : NULL,
+                            NULL, options, 0, bs, &child_backing, &local_err);
+    if (ret < 0) {
+        bdrv_unref(backing_hd);
+        backing_hd = NULL;
+        bs->open_flags |= BDRV_O_NO_BACKING;
+        error_setg(errp, "Could not open backing file: %s",
+                   error_get_pretty(local_err));
+        error_free(local_err);
+        goto free_exit;
+    }
+
+    /* Hook up the backing file link; drop our reference, bs owns the
+     * backing_hd reference now */
+    bdrv_set_backing_hd(bs, backing_hd);
+    bdrv_unref(backing_hd);
+
+free_exit:
+    g_free(backing_filename);
+    return ret;
+}
+
+/*
+ * Opens a disk image whose options are given as BlockdevRef in another block
+ * device's options.
+ *
+ * If allow_none is true, no image will be opened if filename is false and no
+ * BlockdevRef is given. NULL will be returned, but errp remains unset.
+ *
+ * bdrev_key specifies the key for the image's BlockdevRef in the options QDict.
+ * That QDict has to be flattened; therefore, if the BlockdevRef is a QDict
+ * itself, all options starting with "${bdref_key}." are considered part of the
+ * BlockdevRef.
+ *
+ * The BlockdevRef will be removed from the options QDict.
+ */
+BdrvChild *bdrv_open_child(const char *filename,
+                           QDict *options, const char *bdref_key,
+                           BlockDriverState* parent,
+                           const BdrvChildRole *child_role,
+                           bool allow_none, Error **errp)
+{
+    BdrvChild *c = NULL;
+    BlockDriverState *bs;
+    QDict *image_options;
+    int ret;
+    char *bdref_key_dot;
+    const char *reference;
+
+    assert(child_role != NULL);
+
+    bdref_key_dot = g_strdup_printf("%s.", bdref_key);
+    qdict_extract_subqdict(options, &image_options, bdref_key_dot);
+    g_free(bdref_key_dot);
+
+    reference = qdict_get_try_str(options, bdref_key);
+    if (!filename && !reference && !qdict_size(image_options)) {
+        if (!allow_none) {
+            error_setg(errp, "A block device must be specified for \"%s\"",
+                       bdref_key);
+        }
+        QDECREF(image_options);
+        goto done;
+    }
+
+    bs = NULL;
+    ret = bdrv_open_inherit(&bs, filename, reference, image_options, 0,
+                            parent, child_role, errp);
+    if (ret < 0) {
+        goto done;
+    }
+
+    c = bdrv_attach_child(parent, bs, child_role);
+
+done:
+    qdict_del(options, bdref_key);
+    return c;
+}
+
+int bdrv_append_temp_snapshot(BlockDriverState *bs, int flags, Error **errp)
+{
+    /* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */
+    char *tmp_filename = g_malloc0(PATH_MAX + 1);
+    int64_t total_size;
+    QemuOpts *opts = NULL;
+    QDict *snapshot_options;
+    BlockDriverState *bs_snapshot;
+    Error *local_err = NULL;
+    int ret;
+
+    /* if snapshot, we create a temporary backing file and open it
+       instead of opening 'filename' directly */
+
+    /* Get the required size from the image */
+    total_size = bdrv_getlength(bs);
+    if (total_size < 0) {
+        ret = total_size;
+        error_setg_errno(errp, -total_size, "Could not get image size");
+        goto out;
+    }
+
+    /* Create the temporary image */
+    ret = get_tmp_filename(tmp_filename, PATH_MAX + 1);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not get temporary filename");
+        goto out;
+    }
+
+    opts = qemu_opts_create(bdrv_qcow2.create_opts, NULL, 0,
+                            &error_abort);
+    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, total_size, &error_abort);
+    ret = bdrv_create(&bdrv_qcow2, tmp_filename, opts, &local_err);
+    qemu_opts_del(opts);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not create temporary overlay "
+                         "'%s': %s", tmp_filename,
+                         error_get_pretty(local_err));
+        error_free(local_err);
+        goto out;
+    }
+
+    /* Prepare a new options QDict for the temporary file */
+    snapshot_options = qdict_new();
+    qdict_put(snapshot_options, "file.driver",
+              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, &local_err);
+    if (ret < 0) {
+        error_propagate(errp, local_err);
+        goto out;
+    }
+
+    bdrv_append(bs_snapshot, bs);
+
+out:
+    g_free(tmp_filename);
+    return ret;
+}
+
+/*
+ * Opens a disk image (raw, qcow2, vmdk, ...)
+ *
+ * options is a QDict of options to pass to the block drivers, or NULL for an
+ * empty set of options. The reference to the QDict belongs to the block layer
+ * after the call (even on failure), so if the caller intends to reuse the
+ * dictionary, it needs to use QINCREF() before calling bdrv_open.
+ *
+ * If *pbs is NULL, a new BDS will be created with a pointer to it stored there.
+ * If it is not NULL, the referenced BDS will be reused.
+ *
+ * The reference parameter may be used to specify an existing block device which
+ * should be opened. If specified, neither options nor a filename may be given,
+ * nor can an existing BDS be reused (that is, *pbs has to be NULL).
+ */
+static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
+                             const char *reference, QDict *options, int flags,
+                             BlockDriverState *parent,
+                             const BdrvChildRole *child_role, Error **errp)
+{
+    int ret;
+    BdrvChild *file = NULL;
+    BlockDriverState *bs;
+    BlockDriver *drv = NULL;
+    const char *drvname;
+    const char *backing;
+    Error *local_err = NULL;
+    int snapshot_flags = 0;
+
+    assert(pbs);
+    assert(!child_role || !flags);
+    assert(!child_role == !parent);
+
+    if (reference) {
+        bool options_non_empty = options ? qdict_size(options) : false;
+        QDECREF(options);
+
+        if (*pbs) {
+            error_setg(errp, "Cannot reuse an existing BDS when referencing "
+                       "another block device");
+            return -EINVAL;
+        }
+
+        if (filename || options_non_empty) {
+            error_setg(errp, "Cannot reference an existing block device with "
+                       "additional options or a new filename");
+            return -EINVAL;
+        }
+
+        bs = bdrv_lookup_bs(reference, reference, errp);
+        if (!bs) {
+            return -ENODEV;
+        }
+        bdrv_ref(bs);
+        *pbs = bs;
+        return 0;
+    }
+
+    if (*pbs) {
+        bs = *pbs;
+    } else {
+        bs = bdrv_new();
+    }
+
+    /* NULL means an empty set of options */
+    if (options == NULL) {
+        options = qdict_new();
+    }
+
+    if (child_role) {
+        bs->inherits_from = parent;
+        flags = child_role->inherit_flags(parent->open_flags);
+    }
+
+    ret = bdrv_fill_options(&options, &filename, &flags, &local_err);
+    if (local_err) {
+        goto fail;
+    }
+
+    /* Find the right image format driver */
+    drvname = qdict_get_try_str(options, "driver");
+    if (drvname) {
+        drv = bdrv_find_format(drvname);
+        qdict_del(options, "driver");
+        if (!drv) {
+            error_setg(errp, "Unknown driver: '%s'", drvname);
+            ret = -EINVAL;
+            goto fail;
+        }
+    }
+
+    assert(drvname || !(flags & BDRV_O_PROTOCOL));
+
+    backing = qdict_get_try_str(options, "backing");
+    if (backing && *backing == '\0') {
+        flags |= BDRV_O_NO_BACKING;
+        qdict_del(options, "backing");
+    }
+
+    bs->open_flags = flags;
+    bs->options = options;
+    options = qdict_clone_shallow(options);
+
+    /* Open image file without format layer */
+    if ((flags & BDRV_O_PROTOCOL) == 0) {
+        if (flags & BDRV_O_RDWR) {
+            flags |= BDRV_O_ALLOW_RDWR;
+        }
+        if (flags & BDRV_O_SNAPSHOT) {
+            snapshot_flags = bdrv_temp_snapshot_flags(flags);
+            flags = bdrv_backing_flags(flags);
+        }
+
+        bs->open_flags = flags;
+
+        file = bdrv_open_child(filename, options, "file", bs,
+                               &child_file, true, &local_err);
+        if (local_err) {
+            ret = -EINVAL;
+            goto fail;
+        }
+    }
+
+    /* Image format probing */
+    bs->probed = !drv;
+    if (!drv && file) {
+        ret = find_image_format(file->bs, filename, &drv, &local_err);
+        if (ret < 0) {
+            goto fail;
+        }
+    } else if (!drv) {
+        error_setg(errp, "Must specify either driver or file");
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    /* BDRV_O_PROTOCOL must be set iff a protocol BDS is about to be created */
+    assert(!!(flags & BDRV_O_PROTOCOL) == !!drv->bdrv_file_open);
+    /* file must be NULL if a protocol BDS is about to be created
+     * (the inverse results in an error message from bdrv_open_common()) */
+    assert(!(flags & BDRV_O_PROTOCOL) || !file);
+
+    /* Open the image */
+    ret = bdrv_open_common(bs, file, options, flags, drv, &local_err);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    if (file && (bs->file != file)) {
+        bdrv_unref_child(bs, file);
+        file = NULL;
+    }
+
+    /* If there is a backing file, use it */
+    if ((flags & BDRV_O_NO_BACKING) == 0) {
+        QDict *backing_options;
+
+        qdict_extract_subqdict(options, &backing_options, "backing.");
+        ret = bdrv_open_backing_file(bs, backing_options, &local_err);
+        if (ret < 0) {
+            goto close_and_fail;
+        }
+    }
+
+    bdrv_refresh_filename(bs);
+
+    /* Check if any unknown options were used */
+    if (options && (qdict_size(options) != 0)) {
+        const QDictEntry *entry = qdict_first(options);
+        if (flags & BDRV_O_PROTOCOL) {
+            error_setg(errp, "Block protocol '%s' doesn't support the option "
+                       "'%s'", drv->format_name, entry->key);
+        } else {
+            error_setg(errp, "Block format '%s' used by device '%s' doesn't "
+                       "support the option '%s'", drv->format_name,
+                       bdrv_get_device_name(bs), entry->key);
+        }
+
+        ret = -EINVAL;
+        goto close_and_fail;
+    }
+
+    if (!bdrv_key_required(bs)) {
+        if (bs->blk) {
+            blk_dev_change_media_cb(bs->blk, true);
+        }
+    } else if (!runstate_check(RUN_STATE_PRELAUNCH)
+               && !runstate_check(RUN_STATE_INMIGRATE)
+               && !runstate_check(RUN_STATE_PAUSED)) { /* HACK */
+        error_setg(errp,
+                   "Guest must be stopped for opening of encrypted image");
+        ret = -EBUSY;
+        goto close_and_fail;
+    }
+
+    QDECREF(options);
+    *pbs = bs;
+
+    /* For snapshot=on, create a temporary qcow2 overlay. bs points to the
+     * temporary snapshot afterwards. */
+    if (snapshot_flags) {
+        ret = bdrv_append_temp_snapshot(bs, snapshot_flags, &local_err);
+        if (local_err) {
+            goto close_and_fail;
+        }
+    }
+
+    return 0;
+
+fail:
+    if (file != NULL) {
+        bdrv_unref_child(bs, file);
+    }
+    QDECREF(bs->options);
+    QDECREF(options);
+    bs->options = NULL;
+    if (!*pbs) {
+        /* If *pbs is NULL, a new BDS has been created in this function and
+           needs to be freed now. Otherwise, it does not need to be closed,
+           since it has not really been opened yet. */
+        bdrv_unref(bs);
+    }
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
+    return ret;
+
+close_and_fail:
+    /* See fail path, but now the BDS has to be always closed */
+    if (*pbs) {
+        bdrv_close(bs);
+    } else {
+        bdrv_unref(bs);
+    }
+    QDECREF(options);
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
+    return ret;
+}
+
+int bdrv_open(BlockDriverState **pbs, const char *filename,
+              const char *reference, QDict *options, int flags, Error **errp)
+{
+    return bdrv_open_inherit(pbs, filename, reference, options, flags, NULL,
+                             NULL, errp);
+}
+
+typedef struct BlockReopenQueueEntry {
+     bool prepared;
+     BDRVReopenState state;
+     QSIMPLEQ_ENTRY(BlockReopenQueueEntry) entry;
+} BlockReopenQueueEntry;
+
+/*
+ * Adds a BlockDriverState to a simple queue for an atomic, transactional
+ * reopen of multiple devices.
+ *
+ * bs_queue can either be an existing BlockReopenQueue that has had QSIMPLE_INIT
+ * already performed, or alternatively may be NULL a new BlockReopenQueue will
+ * be created and initialized. This newly created BlockReopenQueue should be
+ * passed back in for subsequent calls that are intended to be of the same
+ * atomic 'set'.
+ *
+ * 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
+ * bs_queue, or the existing bs_queue being used.
+ *
+ */
+BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
+                                    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;
+
+    QLIST_FOREACH(child, &bs->children, next) {
+        int child_flags;
+
+        if (child->bs->inherits_from != bs) {
+            continue;
+        }
+
+        child_flags = child->role->inherit_flags(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;
+}
+
+/*
+ * Reopen multiple BlockDriverStates atomically & transactionally.
+ *
+ * The queue passed in (bs_queue) must have been built up previous
+ * via bdrv_reopen_queue().
+ *
+ * Reopens all BDS specified in the queue, with the appropriate
+ * flags.  All devices are prepared for reopen, and failure of any
+ * device will cause all device changes to be abandonded, and intermediate
+ * data cleaned up.
+ *
+ * If all devices prepare successfully, then the changes are committed
+ * to all devices.
+ *
+ */
+int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
+{
+    int ret = -1;
+    BlockReopenQueueEntry *bs_entry, *next;
+    Error *local_err = NULL;
+
+    assert(bs_queue != NULL);
+
+    bdrv_drain_all();
+
+    QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
+        if (bdrv_reopen_prepare(&bs_entry->state, bs_queue, &local_err)) {
+            error_propagate(errp, local_err);
+            goto cleanup;
+        }
+        bs_entry->prepared = true;
+    }
+
+    /* If we reach this point, we have success and just need to apply the
+     * changes
+     */
+    QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
+        bdrv_reopen_commit(&bs_entry->state);
+    }
+
+    ret = 0;
+
+cleanup:
+    QSIMPLEQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
+        if (ret && bs_entry->prepared) {
+            bdrv_reopen_abort(&bs_entry->state);
+        }
+        QDECREF(bs_entry->state.options);
+        g_free(bs_entry);
+    }
+    g_free(bs_queue);
+    return ret;
+}
+
+
+/* Reopen a single BlockDriverState with the specified flags. */
+int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp)
+{
+    int ret = -1;
+    Error *local_err = NULL;
+    BlockReopenQueue *queue = bdrv_reopen_queue(NULL, bs, NULL, bdrv_flags);
+
+    ret = bdrv_reopen_multiple(queue, &local_err);
+    if (local_err != NULL) {
+        error_propagate(errp, local_err);
+    }
+    return ret;
+}
+
+
+/*
+ * Prepares a BlockDriverState for reopen. All changes are staged in the
+ * 'opaque' field of the BDRVReopenState, which is used and allocated by
+ * the block driver layer .bdrv_reopen_prepare()
+ *
+ * bs is the BlockDriverState to reopen
+ * flags are the new open flags
+ * queue is the reopen queue
+ *
+ * Returns 0 on success, non-zero on error.  On error errp will be set
+ * as well.
+ *
+ * On failure, bdrv_reopen_abort() will be called to clean up any data.
+ * It is the responsibility of the caller to then call the abort() or
+ * commit() for any other BDS that have been left in a prepare() state
+ *
+ */
+int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
+                        Error **errp)
+{
+    int ret = -1;
+    Error *local_err = NULL;
+    BlockDriver *drv;
+
+    assert(reopen_state != NULL);
+    assert(reopen_state->bs->drv != NULL);
+    drv = reopen_state->bs->drv;
+
+    /* if we are to stay read-only, do not allow permission change
+     * to r/w */
+    if (!(reopen_state->bs->open_flags & BDRV_O_ALLOW_RDWR) &&
+        reopen_state->flags & BDRV_O_RDWR) {
+        error_setg(errp, "Node '%s' is read only",
+                   bdrv_get_device_or_node_name(reopen_state->bs));
+        goto error;
+    }
+
+
+    ret = bdrv_flush(reopen_state->bs);
+    if (ret) {
+        error_setg_errno(errp, -ret, "Error flushing drive");
+        goto error;
+    }
+
+    if (drv->bdrv_reopen_prepare) {
+        ret = drv->bdrv_reopen_prepare(reopen_state, queue, &local_err);
+        if (ret) {
+            if (local_err != NULL) {
+                error_propagate(errp, local_err);
+            } else {
+                error_setg(errp, "failed while preparing to reopen image '%s'",
+                           reopen_state->bs->filename);
+            }
+            goto error;
+        }
+    } else {
+        /* It is currently mandatory to have a bdrv_reopen_prepare()
+         * handler for each supported drv. */
+        error_setg(errp, "Block format '%s' used by node '%s' "
+                   "does not support reopening files", drv->format_name,
+                   bdrv_get_device_or_node_name(reopen_state->bs));
+        ret = -1;
+        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:
+    return ret;
+}
+
+/*
+ * Takes the staged changes for the reopen from bdrv_reopen_prepare(), and
+ * makes them final by swapping the staging BlockDriverState contents into
+ * the active BlockDriverState contents.
+ */
+void bdrv_reopen_commit(BDRVReopenState *reopen_state)
+{
+    BlockDriver *drv;
+
+    assert(reopen_state != NULL);
+    drv = reopen_state->bs->drv;
+    assert(drv != NULL);
+
+    /* If there are any driver level actions to take */
+    if (drv->bdrv_reopen_commit) {
+        drv->bdrv_reopen_commit(reopen_state);
+    }
+
+    /* set BDS specific flags now */
+    reopen_state->bs->open_flags         = reopen_state->flags;
+    reopen_state->bs->enable_write_cache = !!(reopen_state->flags &
+                                              BDRV_O_CACHE_WB);
+    reopen_state->bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
+
+    bdrv_refresh_limits(reopen_state->bs, NULL);
+}
+
+/*
+ * Abort the reopen, and delete and free the staged changes in
+ * reopen_state
+ */
+void bdrv_reopen_abort(BDRVReopenState *reopen_state)
+{
+    BlockDriver *drv;
+
+    assert(reopen_state != NULL);
+    drv = reopen_state->bs->drv;
+    assert(drv != NULL);
+
+    if (drv->bdrv_reopen_abort) {
+        drv->bdrv_reopen_abort(reopen_state);
+    }
+}
+
+
+void bdrv_close(BlockDriverState *bs)
+{
+    BdrvAioNotifier *ban, *ban_next;
+
+    if (bs->job) {
+        block_job_cancel_sync(bs->job);
+    }
+
+    /* Disable I/O limits and drain all pending throttled requests */
+    if (bs->throttle_state) {
+        bdrv_io_limits_disable(bs);
+    }
+
+    bdrv_drain(bs); /* complete I/O */
+    bdrv_flush(bs);
+    bdrv_drain(bs); /* in case flush left pending I/O */
+    notifier_list_notify(&bs->close_notifiers, bs);
+
+    if (bs->blk) {
+        blk_dev_change_media_cb(bs->blk, false);
+    }
+
+    if (bs->drv) {
+        BdrvChild *child, *next;
+
+        bs->drv->bdrv_close(bs);
+        bs->drv = NULL;
+
+        bdrv_set_backing_hd(bs, NULL);
+
+        if (bs->file != NULL) {
+            bdrv_unref_child(bs, bs->file);
+            bs->file = NULL;
+        }
+
+        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
+            /* TODO Remove bdrv_unref() from drivers' close function and use
+             * bdrv_unref_child() here */
+            if (child->bs->inherits_from == bs) {
+                child->bs->inherits_from = NULL;
+            }
+            bdrv_detach_child(child);
+        }
+
+        g_free(bs->opaque);
+        bs->opaque = NULL;
+        bs->copy_on_read = 0;
+        bs->backing_file[0] = '\0';
+        bs->backing_format[0] = '\0';
+        bs->total_sectors = 0;
+        bs->encrypted = 0;
+        bs->valid_key = 0;
+        bs->sg = 0;
+        bs->zero_beyond_eof = false;
+        QDECREF(bs->options);
+        bs->options = NULL;
+        QDECREF(bs->full_open_options);
+        bs->full_open_options = NULL;
+    }
+
+    QLIST_FOREACH_SAFE(ban, &bs->aio_notifiers, list, ban_next) {
+        g_free(ban);
+    }
+    QLIST_INIT(&bs->aio_notifiers);
+}
+
+void bdrv_close_all(void)
+{
+    BlockDriverState *bs;
+
+    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
+        bdrv_close(bs);
+        aio_context_release(aio_context);
+    }
+}
+
+/* Note that bs->device_list.tqe_prev is initially null,
+ * and gets set to non-null by QTAILQ_INSERT_TAIL().  Establish
+ * the useful invariant "bs in bdrv_states iff bs->tqe_prev" by
+ * resetting it to null on remove.  */
+void bdrv_device_remove(BlockDriverState *bs)
+{
+    QTAILQ_REMOVE(&bdrv_states, bs, device_list);
+    bs->device_list.tqe_prev = NULL;
+}
+
+/* make a BlockDriverState anonymous by removing from bdrv_state and
+ * graph_bdrv_state list.
+   Also, NULL terminate the device_name to prevent double remove */
+void bdrv_make_anon(BlockDriverState *bs)
+{
+    /* Take care to remove bs from bdrv_states only when it's actually
+     * in it. */
+    if (bs->device_list.tqe_prev) {
+        bdrv_device_remove(bs);
+    }
+    if (bs->node_name[0] != '\0') {
+        QTAILQ_REMOVE(&graph_bdrv_states, bs, node_list);
+    }
+    bs->node_name[0] = '\0';
+}
+
+/* Fields that need to stay with the top-level BDS */
+static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
+                                     BlockDriverState *bs_src)
+{
+    /* move some fields that need to stay attached to the device */
+
+    /* dev info */
+    bs_dest->copy_on_read       = bs_src->copy_on_read;
+
+    bs_dest->enable_write_cache = bs_src->enable_write_cache;
+
+    /* dirty bitmap */
+    bs_dest->dirty_bitmaps      = bs_src->dirty_bitmaps;
+}
+
+static void change_parent_backing_link(BlockDriverState *from,
+                                       BlockDriverState *to)
+{
+    BdrvChild *c, *next;
+
+    QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
+        assert(c->role != &child_backing);
+        c->bs = to;
+        QLIST_REMOVE(c, next_parent);
+        QLIST_INSERT_HEAD(&to->parents, c, next_parent);
+        bdrv_ref(to);
+        bdrv_unref(from);
+    }
+    if (from->blk) {
+        blk_set_bs(from->blk, to);
+        if (!to->device_list.tqe_prev) {
+            QTAILQ_INSERT_BEFORE(from, to, device_list);
+        }
+        bdrv_device_remove(from);
+    }
+}
+
+static void swap_feature_fields(BlockDriverState *bs_top,
+                                BlockDriverState *bs_new)
+{
+    BlockDriverState tmp;
+
+    bdrv_move_feature_fields(&tmp, bs_top);
+    bdrv_move_feature_fields(bs_top, bs_new);
+    bdrv_move_feature_fields(bs_new, &tmp);
+
+    assert(!bs_new->throttle_state);
+    if (bs_top->throttle_state) {
+        assert(bs_top->io_limits_enabled);
+        bdrv_io_limits_enable(bs_new, throttle_group_get_name(bs_top));
+        bdrv_io_limits_disable(bs_top);
+    }
+}
+
+/*
+ * Add new bs contents at the top of an image chain while the chain is
+ * live, while keeping required fields on the top layer.
+ *
+ * This will modify the BlockDriverState fields, and swap contents
+ * between bs_new and bs_top. Both bs_new and bs_top are modified.
+ *
+ * bs_new must not be attached to a BlockBackend.
+ *
+ * This function does not create any image files.
+ *
+ * bdrv_append() takes ownership of a bs_new reference and unrefs it because
+ * that's what the callers commonly need. bs_new will be referenced by the old
+ * parents of bs_top after bdrv_append() returns. If the caller needs to keep a
+ * reference of its own, it must call bdrv_ref().
+ */
+void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
+{
+    assert(!bdrv_requests_pending(bs_top));
+    assert(!bdrv_requests_pending(bs_new));
+
+    bdrv_ref(bs_top);
+    change_parent_backing_link(bs_top, bs_new);
+
+    /* Some fields always stay on top of the backing file chain */
+    swap_feature_fields(bs_top, bs_new);
+
+    bdrv_set_backing_hd(bs_new, bs_top);
+    bdrv_unref(bs_top);
+
+    /* bs_new is now referenced by its new parents, we don't need the
+     * additional reference any more. */
+    bdrv_unref(bs_new);
+}
+
+void bdrv_replace_in_backing_chain(BlockDriverState *old, BlockDriverState *new)
+{
+    assert(!bdrv_requests_pending(old));
+    assert(!bdrv_requests_pending(new));
+
+    bdrv_ref(old);
+
+    if (old->blk) {
+        /* As long as these fields aren't in BlockBackend, but in the top-level
+         * BlockDriverState, it's not possible for a BDS to have two BBs.
+         *
+         * We really want to copy the fields from old to new, but we go for a
+         * swap instead so that pointers aren't duplicated and cause trouble.
+         * (Also, bdrv_swap() used to do the same.) */
+        assert(!new->blk);
+        swap_feature_fields(old, new);
+    }
+    change_parent_backing_link(old, new);
+
+    /* Change backing files if a previously independent node is added to the
+     * chain. For active commit, we replace top by its own (indirect) backing
+     * file and don't do anything here so we don't build a loop. */
+    if (new->backing == NULL && !bdrv_chain_contains(backing_bs(old), new)) {
+        bdrv_set_backing_hd(new, backing_bs(old));
+        bdrv_set_backing_hd(old, NULL);
+    }
+
+    bdrv_unref(old);
+}
+
+static void bdrv_delete(BlockDriverState *bs)
+{
+    assert(!bs->job);
+    assert(bdrv_op_blocker_is_empty(bs));
+    assert(!bs->refcnt);
+    assert(QLIST_EMPTY(&bs->dirty_bitmaps));
+
+    bdrv_close(bs);
+
+    /* remove from list, if necessary */
+    bdrv_make_anon(bs);
+
+    g_free(bs);
+}
+
+/*
+ * Run consistency checks on an image
+ *
+ * Returns 0 if the check could be completed (it doesn't mean that the image is
+ * free of errors) or -errno when an internal error occurred. The results of the
+ * check are stored in res.
+ */
+int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix)
+{
+    if (bs->drv == NULL) {
+        return -ENOMEDIUM;
+    }
+    if (bs->drv->bdrv_check == NULL) {
+        return -ENOTSUP;
+    }
+
+    memset(res, 0, sizeof(*res));
+    return bs->drv->bdrv_check(bs, res, fix);
+}
+
+#define COMMIT_BUF_SECTORS 2048
+
+/* commit COW file into the raw image */
+int bdrv_commit(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+    int64_t sector, total_sectors, length, backing_length;
+    int n, ro, open_flags;
+    int ret = 0;
+    uint8_t *buf = NULL;
+
+    if (!drv)
+        return -ENOMEDIUM;
+
+    if (!bs->backing) {
+        return -ENOTSUP;
+    }
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, NULL) ||
+        bdrv_op_is_blocked(bs->backing->bs, BLOCK_OP_TYPE_COMMIT_TARGET, NULL)) {
+        return -EBUSY;
+    }
+
+    ro = bs->backing->bs->read_only;
+    open_flags =  bs->backing->bs->open_flags;
+
+    if (ro) {
+        if (bdrv_reopen(bs->backing->bs, open_flags | BDRV_O_RDWR, NULL)) {
+            return -EACCES;
+        }
+    }
+
+    length = bdrv_getlength(bs);
+    if (length < 0) {
+        ret = length;
+        goto ro_cleanup;
+    }
+
+    backing_length = bdrv_getlength(bs->backing->bs);
+    if (backing_length < 0) {
+        ret = backing_length;
+        goto ro_cleanup;
+    }
+
+    /* If our top snapshot is larger than the backing file image,
+     * grow the backing file image if possible.  If not possible,
+     * we must return an error */
+    if (length > backing_length) {
+        ret = bdrv_truncate(bs->backing->bs, length);
+        if (ret < 0) {
+            goto ro_cleanup;
+        }
+    }
+
+    total_sectors = length >> BDRV_SECTOR_BITS;
+
+    /* qemu_try_blockalign() for bs will choose an alignment that works for
+     * bs->backing->bs as well, so no need to compare the alignment manually. */
+    buf = qemu_try_blockalign(bs, COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);
+    if (buf == NULL) {
+        ret = -ENOMEM;
+        goto ro_cleanup;
+    }
+
+    for (sector = 0; sector < total_sectors; sector += n) {
+        ret = bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n);
+        if (ret < 0) {
+            goto ro_cleanup;
+        }
+        if (ret) {
+            ret = bdrv_read(bs, sector, buf, n);
+            if (ret < 0) {
+                goto ro_cleanup;
+            }
+
+            ret = bdrv_write(bs->backing->bs, sector, buf, n);
+            if (ret < 0) {
+                goto ro_cleanup;
+            }
+        }
+    }
+
+    if (drv->bdrv_make_empty) {
+        ret = drv->bdrv_make_empty(bs);
+        if (ret < 0) {
+            goto ro_cleanup;
+        }
+        bdrv_flush(bs);
+    }
+
+    /*
+     * Make sure all data we wrote to the backing device is actually
+     * stable on disk.
+     */
+    if (bs->backing) {
+        bdrv_flush(bs->backing->bs);
+    }
+
+    ret = 0;
+ro_cleanup:
+    qemu_vfree(buf);
+
+    if (ro) {
+        /* ignoring error return here */
+        bdrv_reopen(bs->backing->bs, open_flags & ~BDRV_O_RDWR, NULL);
+    }
+
+    return ret;
+}
+
+int bdrv_commit_all(void)
+{
+    BlockDriverState *bs;
+
+    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
+        if (bs->drv && bs->backing) {
+            int ret = bdrv_commit(bs);
+            if (ret < 0) {
+                aio_context_release(aio_context);
+                return ret;
+            }
+        }
+        aio_context_release(aio_context);
+    }
+    return 0;
+}
+
+/*
+ * Return values:
+ * 0        - success
+ * -EINVAL  - backing format specified, but no file
+ * -ENOSPC  - can't update the backing file because no space is left in the
+ *            image file header
+ * -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)
+{
+    BlockDriver *drv = bs->drv;
+    int ret;
+
+    /* Backing file format doesn't make sense without a backing file */
+    if (backing_fmt && !backing_file) {
+        return -EINVAL;
+    }
+
+    if (drv->bdrv_change_backing_file != NULL) {
+        ret = drv->bdrv_change_backing_file(bs, backing_file, backing_fmt);
+    } else {
+        ret = -ENOTSUP;
+    }
+
+    if (ret == 0) {
+        pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
+        pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: "");
+    }
+    return ret;
+}
+
+/*
+ * Finds the image layer in the chain that has 'bs' as its backing file.
+ *
+ * active is the current topmost image.
+ *
+ * Returns NULL if bs is not found in active's image chain,
+ * or if active == bs.
+ *
+ * Returns the bottommost base image if bs == NULL.
+ */
+BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
+                                    BlockDriverState *bs)
+{
+    while (active && bs != backing_bs(active)) {
+        active = backing_bs(active);
+    }
+
+    return active;
+}
+
+/* Given a BDS, searches for the base layer. */
+BlockDriverState *bdrv_find_base(BlockDriverState *bs)
+{
+    return bdrv_find_overlay(bs, NULL);
+}
+
+/*
+ * Drops images above 'base' up to and including 'top', and sets the image
+ * above 'top' to have base as its backing file.
+ *
+ * Requires that the overlay to 'top' is opened r/w, so that the backing file
+ * information in 'bs' can be properly updated.
+ *
+ * E.g., this will convert the following chain:
+ * bottom <- base <- intermediate <- top <- active
+ *
+ * to
+ *
+ * bottom <- base <- active
+ *
+ * It is allowed for bottom==base, in which case it converts:
+ *
+ * base <- intermediate <- top <- active
+ *
+ * to
+ *
+ * base <- active
+ *
+ * If backing_file_str is non-NULL, it will be used when modifying top's
+ * overlay image metadata.
+ *
+ * Error conditions:
+ *  if active == top, that is considered an error
+ *
+ */
+int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top,
+                           BlockDriverState *base, const char *backing_file_str)
+{
+    BlockDriverState *new_top_bs = NULL;
+    int ret = -EIO;
+
+    if (!top->drv || !base->drv) {
+        goto exit;
+    }
+
+    new_top_bs = bdrv_find_overlay(active, top);
+
+    if (new_top_bs == NULL) {
+        /* we could not find the image above 'top', this is an error */
+        goto exit;
+    }
+
+    /* special case of new_top_bs->backing->bs already pointing to base - nothing
+     * to do, no intermediate images */
+    if (backing_bs(new_top_bs) == base) {
+        ret = 0;
+        goto exit;
+    }
+
+    /* Make sure that base is in the backing chain of top */
+    if (!bdrv_chain_contains(top, base)) {
+        goto exit;
+    }
+
+    /* success - we can delete the intermediate states, and link top->base */
+    backing_file_str = backing_file_str ? backing_file_str : base->filename;
+    ret = bdrv_change_backing_file(new_top_bs, backing_file_str,
+                                   base->drv ? base->drv->format_name : "");
+    if (ret) {
+        goto exit;
+    }
+    bdrv_set_backing_hd(new_top_bs, base);
+
+    ret = 0;
+exit:
+    return ret;
+}
+
+/**
+ * Truncate file to 'offset' bytes (needed only for file protocols)
+ */
+int bdrv_truncate(BlockDriverState *bs, int64_t offset)
+{
+    BlockDriver *drv = bs->drv;
+    int ret;
+    if (!drv)
+        return -ENOMEDIUM;
+    if (!drv->bdrv_truncate)
+        return -ENOTSUP;
+    if (bs->read_only)
+        return -EACCES;
+
+    ret = drv->bdrv_truncate(bs, offset);
+    if (ret == 0) {
+        ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
+        bdrv_dirty_bitmap_truncate(bs);
+        if (bs->blk) {
+            blk_dev_resize_cb(bs->blk);
+        }
+    }
+    return ret;
+}
+
+/**
+ * Length of a allocated file in bytes. Sparse files are counted by actual
+ * allocated space. Return < 0 if error or unknown.
+ */
+int64_t bdrv_get_allocated_file_size(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+    if (!drv) {
+        return -ENOMEDIUM;
+    }
+    if (drv->bdrv_get_allocated_file_size) {
+        return drv->bdrv_get_allocated_file_size(bs);
+    }
+    if (bs->file) {
+        return bdrv_get_allocated_file_size(bs->file->bs);
+    }
+    return -ENOTSUP;
+}
+
+/**
+ * Return number of sectors on success, -errno on error.
+ */
+int64_t bdrv_nb_sectors(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (!drv)
+        return -ENOMEDIUM;
+
+    if (drv->has_variable_length) {
+        int ret = refresh_total_sectors(bs, bs->total_sectors);
+        if (ret < 0) {
+            return ret;
+        }
+    }
+    return bs->total_sectors;
+}
+
+/**
+ * Return length in bytes on success, -errno on error.
+ * The length is always a multiple of BDRV_SECTOR_SIZE.
+ */
+int64_t bdrv_getlength(BlockDriverState *bs)
+{
+    int64_t ret = bdrv_nb_sectors(bs);
+
+    ret = ret > INT64_MAX / BDRV_SECTOR_SIZE ? -EFBIG : ret;
+    return ret < 0 ? ret : ret * BDRV_SECTOR_SIZE;
+}
+
+/* return 0 as number of sectors if no device present or error */
+void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)
+{
+    int64_t nb_sectors = bdrv_nb_sectors(bs);
+
+    *nb_sectors_ptr = nb_sectors < 0 ? 0 : nb_sectors;
+}
+
+int bdrv_is_read_only(BlockDriverState *bs)
+{
+    return bs->read_only;
+}
+
+int bdrv_is_sg(BlockDriverState *bs)
+{
+    return bs->sg;
+}
+
+int bdrv_enable_write_cache(BlockDriverState *bs)
+{
+    return bs->enable_write_cache;
+}
+
+void bdrv_set_enable_write_cache(BlockDriverState *bs, bool wce)
+{
+    bs->enable_write_cache = wce;
+
+    /* so a reopen() will preserve wce */
+    if (wce) {
+        bs->open_flags |= BDRV_O_CACHE_WB;
+    } else {
+        bs->open_flags &= ~BDRV_O_CACHE_WB;
+    }
+}
+
+int bdrv_is_encrypted(BlockDriverState *bs)
+{
+    if (bs->backing && bs->backing->bs->encrypted) {
+        return 1;
+    }
+    return bs->encrypted;
+}
+
+int bdrv_key_required(BlockDriverState *bs)
+{
+    BdrvChild *backing = bs->backing;
+
+    if (backing && backing->bs->encrypted && !backing->bs->valid_key) {
+        return 1;
+    }
+    return (bs->encrypted && !bs->valid_key);
+}
+
+int bdrv_set_key(BlockDriverState *bs, const char *key)
+{
+    int ret;
+    if (bs->backing && bs->backing->bs->encrypted) {
+        ret = bdrv_set_key(bs->backing->bs, key);
+        if (ret < 0)
+            return ret;
+        if (!bs->encrypted)
+            return 0;
+    }
+    if (!bs->encrypted) {
+        return -EINVAL;
+    } else if (!bs->drv || !bs->drv->bdrv_set_key) {
+        return -ENOMEDIUM;
+    }
+    ret = bs->drv->bdrv_set_key(bs, key);
+    if (ret < 0) {
+        bs->valid_key = 0;
+    } else if (!bs->valid_key) {
+        bs->valid_key = 1;
+        if (bs->blk) {
+            /* call the change callback now, we skipped it on open */
+            blk_dev_change_media_cb(bs->blk, true);
+        }
+    }
+    return ret;
+}
+
+/*
+ * Provide an encryption key for @bs.
+ * If @key is non-null:
+ *     If @bs is not encrypted, fail.
+ *     Else if the key is invalid, fail.
+ *     Else set @bs's key to @key, replacing the existing key, if any.
+ * If @key is null:
+ *     If @bs is encrypted and still lacks a key, fail.
+ *     Else do nothing.
+ * On failure, store an error object through @errp if non-null.
+ */
+void bdrv_add_key(BlockDriverState *bs, const char *key, Error **errp)
+{
+    if (key) {
+        if (!bdrv_is_encrypted(bs)) {
+            error_setg(errp, "Node '%s' is not encrypted",
+                      bdrv_get_device_or_node_name(bs));
+        } else if (bdrv_set_key(bs, key) < 0) {
+            error_setg(errp, QERR_INVALID_PASSWORD);
+        }
+    } else {
+        if (bdrv_key_required(bs)) {
+            error_set(errp, ERROR_CLASS_DEVICE_ENCRYPTED,
+                      "'%s' (%s) is encrypted",
+                      bdrv_get_device_or_node_name(bs),
+                      bdrv_get_encrypted_filename(bs));
+        }
+    }
+}
+
+const char *bdrv_get_format_name(BlockDriverState *bs)
+{
+    return bs->drv ? bs->drv->format_name : NULL;
+}
+
+static int qsort_strcmp(const void *a, const void *b)
+{
+    return strcmp(a, b);
+}
+
+void bdrv_iterate_format(void (*it)(void *opaque, const char *name),
+                         void *opaque)
+{
+    BlockDriver *drv;
+    int count = 0;
+    int i;
+    const char **formats = NULL;
+
+    QLIST_FOREACH(drv, &bdrv_drivers, list) {
+        if (drv->format_name) {
+            bool found = false;
+            int i = count;
+            while (formats && i && !found) {
+                found = !strcmp(formats[--i], drv->format_name);
+            }
+
+            if (!found) {
+                formats = g_renew(const char *, formats, count + 1);
+                formats[count++] = drv->format_name;
+            }
+        }
+    }
+
+    qsort(formats, count, sizeof(formats[0]), qsort_strcmp);
+
+    for (i = 0; i < count; i++) {
+        it(opaque, formats[i]);
+    }
+
+    g_free(formats);
+}
+
+/* This function is to find a node in the bs graph */
+BlockDriverState *bdrv_find_node(const char *node_name)
+{
+    BlockDriverState *bs;
+
+    assert(node_name);
+
+    QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
+        if (!strcmp(node_name, bs->node_name)) {
+            return bs;
+        }
+    }
+    return NULL;
+}
+
+/* Put this QMP function here so it can access the static graph_bdrv_states. */
+BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp)
+{
+    BlockDeviceInfoList *list, *entry;
+    BlockDriverState *bs;
+
+    list = NULL;
+    QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
+        BlockDeviceInfo *info = bdrv_block_device_info(bs, errp);
+        if (!info) {
+            qapi_free_BlockDeviceInfoList(list);
+            return NULL;
+        }
+        entry = g_malloc0(sizeof(*entry));
+        entry->value = info;
+        entry->next = list;
+        list = entry;
+    }
+
+    return list;
+}
+
+BlockDriverState *bdrv_lookup_bs(const char *device,
+                                 const char *node_name,
+                                 Error **errp)
+{
+    BlockBackend *blk;
+    BlockDriverState *bs;
+
+    if (device) {
+        blk = blk_by_name(device);
+
+        if (blk) {
+            bs = blk_bs(blk);
+            if (!bs) {
+                error_setg(errp, "Device '%s' has no medium", device);
+            }
+
+            return bs;
+        }
+    }
+
+    if (node_name) {
+        bs = bdrv_find_node(node_name);
+
+        if (bs) {
+            return bs;
+        }
+    }
+
+    error_setg(errp, "Cannot find device=%s nor node_name=%s",
+                     device ? device : "",
+                     node_name ? node_name : "");
+    return NULL;
+}
+
+/* If 'base' is in the same chain as 'top', return true. Otherwise,
+ * return false.  If either argument is NULL, return false. */
+bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
+{
+    while (top && top != base) {
+        top = backing_bs(top);
+    }
+
+    return top != NULL;
+}
+
+BlockDriverState *bdrv_next_node(BlockDriverState *bs)
+{
+    if (!bs) {
+        return QTAILQ_FIRST(&graph_bdrv_states);
+    }
+    return QTAILQ_NEXT(bs, node_list);
+}
+
+BlockDriverState *bdrv_next(BlockDriverState *bs)
+{
+    if (!bs) {
+        return QTAILQ_FIRST(&bdrv_states);
+    }
+    return QTAILQ_NEXT(bs, device_list);
+}
+
+const char *bdrv_get_node_name(const BlockDriverState *bs)
+{
+    return bs->node_name;
+}
+
+/* TODO check what callers really want: bs->node_name or blk_name() */
+const char *bdrv_get_device_name(const BlockDriverState *bs)
+{
+    return bs->blk ? blk_name(bs->blk) : "";
+}
+
+/* This can be used to identify nodes that might not have a device
+ * name associated. Since node and device names live in the same
+ * namespace, the result is unambiguous. The exception is if both are
+ * absent, then this returns an empty (non-null) string. */
+const char *bdrv_get_device_or_node_name(const BlockDriverState *bs)
+{
+    return bs->blk ? blk_name(bs->blk) : bs->node_name;
+}
+
+int bdrv_get_flags(BlockDriverState *bs)
+{
+    return bs->open_flags;
+}
+
+int bdrv_has_zero_init_1(BlockDriverState *bs)
+{
+    return 1;
+}
+
+int bdrv_has_zero_init(BlockDriverState *bs)
+{
+    assert(bs->drv);
+
+    /* If BS is a copy on write image, it is initialized to
+       the contents of the base image, which may not be zeroes.  */
+    if (bs->backing) {
+        return 0;
+    }
+    if (bs->drv->bdrv_has_zero_init) {
+        return bs->drv->bdrv_has_zero_init(bs);
+    }
+
+    /* safe default */
+    return 0;
+}
+
+bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs)
+{
+    BlockDriverInfo bdi;
+
+    if (bs->backing) {
+        return false;
+    }
+
+    if (bdrv_get_info(bs, &bdi) == 0) {
+        return bdi.unallocated_blocks_are_zero;
+    }
+
+    return false;
+}
+
+bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs)
+{
+    BlockDriverInfo bdi;
+
+    if (bs->backing || !(bs->open_flags & BDRV_O_UNMAP)) {
+        return false;
+    }
+
+    if (bdrv_get_info(bs, &bdi) == 0) {
+        return bdi.can_write_zeroes_with_unmap;
+    }
+
+    return false;
+}
+
+const char *bdrv_get_encrypted_filename(BlockDriverState *bs)
+{
+    if (bs->backing && bs->backing->bs->encrypted)
+        return bs->backing_file;
+    else if (bs->encrypted)
+        return bs->filename;
+    else
+        return NULL;
+}
+
+void bdrv_get_backing_filename(BlockDriverState *bs,
+                               char *filename, int filename_size)
+{
+    pstrcpy(filename, filename_size, bs->backing_file);
+}
+
+int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
+{
+    BlockDriver *drv = bs->drv;
+    if (!drv)
+        return -ENOMEDIUM;
+    if (!drv->bdrv_get_info)
+        return -ENOTSUP;
+    memset(bdi, 0, sizeof(*bdi));
+    return drv->bdrv_get_info(bs, bdi);
+}
+
+ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+    if (drv && drv->bdrv_get_specific_info) {
+        return drv->bdrv_get_specific_info(bs);
+    }
+    return NULL;
+}
+
+void bdrv_debug_event(BlockDriverState *bs, BlkDebugEvent event)
+{
+    if (!bs || !bs->drv || !bs->drv->bdrv_debug_event) {
+        return;
+    }
+
+    bs->drv->bdrv_debug_event(bs, event);
+}
+
+int bdrv_debug_breakpoint(BlockDriverState *bs, const char *event,
+                          const char *tag)
+{
+    while (bs && bs->drv && !bs->drv->bdrv_debug_breakpoint) {
+        bs = bs->file ? bs->file->bs : NULL;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_breakpoint) {
+        return bs->drv->bdrv_debug_breakpoint(bs, event, tag);
+    }
+
+    return -ENOTSUP;
+}
+
+int bdrv_debug_remove_breakpoint(BlockDriverState *bs, const char *tag)
+{
+    while (bs && bs->drv && !bs->drv->bdrv_debug_remove_breakpoint) {
+        bs = bs->file ? bs->file->bs : NULL;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_remove_breakpoint) {
+        return bs->drv->bdrv_debug_remove_breakpoint(bs, tag);
+    }
+
+    return -ENOTSUP;
+}
+
+int bdrv_debug_resume(BlockDriverState *bs, const char *tag)
+{
+    while (bs && (!bs->drv || !bs->drv->bdrv_debug_resume)) {
+        bs = bs->file ? bs->file->bs : NULL;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_resume) {
+        return bs->drv->bdrv_debug_resume(bs, tag);
+    }
+
+    return -ENOTSUP;
+}
+
+bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag)
+{
+    while (bs && bs->drv && !bs->drv->bdrv_debug_is_suspended) {
+        bs = bs->file ? bs->file->bs : NULL;
+    }
+
+    if (bs && bs->drv && bs->drv->bdrv_debug_is_suspended) {
+        return bs->drv->bdrv_debug_is_suspended(bs, tag);
+    }
+
+    return false;
+}
+
+int bdrv_is_snapshot(BlockDriverState *bs)
+{
+    return !!(bs->open_flags & BDRV_O_SNAPSHOT);
+}
+
+/* backing_file can either be relative, or absolute, or a protocol.  If it is
+ * relative, it must be relative to the chain.  So, passing in bs->filename
+ * from a BDS as backing_file should not be done, as that may be relative to
+ * the CWD rather than the chain. */
+BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
+        const char *backing_file)
+{
+    char *filename_full = NULL;
+    char *backing_file_full = NULL;
+    char *filename_tmp = NULL;
+    int is_protocol = 0;
+    BlockDriverState *curr_bs = NULL;
+    BlockDriverState *retval = NULL;
+
+    if (!bs || !bs->drv || !backing_file) {
+        return NULL;
+    }
+
+    filename_full     = g_malloc(PATH_MAX);
+    backing_file_full = g_malloc(PATH_MAX);
+    filename_tmp      = g_malloc(PATH_MAX);
+
+    is_protocol = path_has_protocol(backing_file);
+
+    for (curr_bs = bs; curr_bs->backing; curr_bs = curr_bs->backing->bs) {
+
+        /* If either of the filename paths is actually a protocol, then
+         * compare unmodified paths; otherwise make paths relative */
+        if (is_protocol || path_has_protocol(curr_bs->backing_file)) {
+            if (strcmp(backing_file, curr_bs->backing_file) == 0) {
+                retval = curr_bs->backing->bs;
+                break;
+            }
+        } else {
+            /* If not an absolute filename path, make it relative to the current
+             * image's filename path */
+            path_combine(filename_tmp, PATH_MAX, curr_bs->filename,
+                         backing_file);
+
+            /* We are going to compare absolute pathnames */
+            if (!realpath(filename_tmp, filename_full)) {
+                continue;
+            }
+
+            /* We need to make sure the backing filename we are comparing against
+             * is relative to the current image filename (or absolute) */
+            path_combine(filename_tmp, PATH_MAX, curr_bs->filename,
+                         curr_bs->backing_file);
+
+            if (!realpath(filename_tmp, backing_file_full)) {
+                continue;
+            }
+
+            if (strcmp(backing_file_full, filename_full) == 0) {
+                retval = curr_bs->backing->bs;
+                break;
+            }
+        }
+    }
+
+    g_free(filename_full);
+    g_free(backing_file_full);
+    g_free(filename_tmp);
+    return retval;
+}
+
+int bdrv_get_backing_file_depth(BlockDriverState *bs)
+{
+    if (!bs->drv) {
+        return 0;
+    }
+
+    if (!bs->backing) {
+        return 0;
+    }
+
+    return 1 + bdrv_get_backing_file_depth(bs->backing->bs);
+}
+
+void bdrv_init(void)
+{
+    module_call_init(MODULE_INIT_BLOCK);
+}
+
+void bdrv_init_with_whitelist(void)
+{
+    use_bdrv_whitelist = 1;
+    bdrv_init();
+}
+
+void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp)
+{
+    Error *local_err = NULL;
+    int ret;
+
+    if (!bs->drv)  {
+        return;
+    }
+
+    if (!(bs->open_flags & BDRV_O_INCOMING)) {
+        return;
+    }
+    bs->open_flags &= ~BDRV_O_INCOMING;
+
+    if (bs->drv->bdrv_invalidate_cache) {
+        bs->drv->bdrv_invalidate_cache(bs, &local_err);
+    } else if (bs->file) {
+        bdrv_invalidate_cache(bs->file->bs, &local_err);
+    }
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    ret = refresh_total_sectors(bs, bs->total_sectors);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not refresh total sector count");
+        return;
+    }
+}
+
+void bdrv_invalidate_cache_all(Error **errp)
+{
+    BlockDriverState *bs;
+    Error *local_err = NULL;
+
+    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
+        bdrv_invalidate_cache(bs, &local_err);
+        aio_context_release(aio_context);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
+        }
+    }
+}
+
+/**************************************************************/
+/* removable device support */
+
+/**
+ * Return TRUE if the media is present
+ */
+bool bdrv_is_inserted(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+    BdrvChild *child;
+
+    if (!drv) {
+        return false;
+    }
+    if (drv->bdrv_is_inserted) {
+        return drv->bdrv_is_inserted(bs);
+    }
+    QLIST_FOREACH(child, &bs->children, next) {
+        if (!bdrv_is_inserted(child->bs)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+/**
+ * Return whether the media changed since the last call to this
+ * function, or -ENOTSUP if we don't know.  Most drivers don't know.
+ */
+int bdrv_media_changed(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (drv && drv->bdrv_media_changed) {
+        return drv->bdrv_media_changed(bs);
+    }
+    return -ENOTSUP;
+}
+
+/**
+ * If eject_flag is TRUE, eject the media. Otherwise, close the tray
+ */
+void bdrv_eject(BlockDriverState *bs, bool eject_flag)
+{
+    BlockDriver *drv = bs->drv;
+    const char *device_name;
+
+    if (drv && drv->bdrv_eject) {
+        drv->bdrv_eject(bs, eject_flag);
+    }
+
+    device_name = bdrv_get_device_name(bs);
+    if (device_name[0] != '\0') {
+        qapi_event_send_device_tray_moved(device_name,
+                                          eject_flag, &error_abort);
+    }
+}
+
+/**
+ * Lock or unlock the media (if it is locked, the user won't be able
+ * to eject it manually).
+ */
+void bdrv_lock_medium(BlockDriverState *bs, bool locked)
+{
+    BlockDriver *drv = bs->drv;
+
+    trace_bdrv_lock_medium(bs, locked);
+
+    if (drv && drv->bdrv_lock_medium) {
+        drv->bdrv_lock_medium(bs, locked);
+    }
+}
+
+BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs, const char *name)
+{
+    BdrvDirtyBitmap *bm;
+
+    assert(name);
+    QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
+        if (bm->name && !strcmp(name, bm->name)) {
+            return bm;
+        }
+    }
+    return NULL;
+}
+
+void bdrv_dirty_bitmap_make_anon(BdrvDirtyBitmap *bitmap)
+{
+    assert(!bdrv_dirty_bitmap_frozen(bitmap));
+    g_free(bitmap->name);
+    bitmap->name = NULL;
+}
+
+BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
+                                          uint32_t granularity,
+                                          const char *name,
+                                          Error **errp)
+{
+    int64_t bitmap_size;
+    BdrvDirtyBitmap *bitmap;
+    uint32_t sector_granularity;
+
+    assert((granularity & (granularity - 1)) == 0);
+
+    if (name && bdrv_find_dirty_bitmap(bs, name)) {
+        error_setg(errp, "Bitmap already exists: %s", name);
+        return NULL;
+    }
+    sector_granularity = granularity >> BDRV_SECTOR_BITS;
+    assert(sector_granularity);
+    bitmap_size = bdrv_nb_sectors(bs);
+    if (bitmap_size < 0) {
+        error_setg_errno(errp, -bitmap_size, "could not get length of device");
+        errno = -bitmap_size;
+        return NULL;
+    }
+    bitmap = g_new0(BdrvDirtyBitmap, 1);
+    bitmap->bitmap = hbitmap_alloc(bitmap_size, ctz32(sector_granularity));
+    bitmap->size = bitmap_size;
+    bitmap->name = g_strdup(name);
+    bitmap->disabled = false;
+    QLIST_INSERT_HEAD(&bs->dirty_bitmaps, bitmap, list);
+    return bitmap;
+}
+
+bool bdrv_dirty_bitmap_frozen(BdrvDirtyBitmap *bitmap)
+{
+    return bitmap->successor;
+}
+
+bool bdrv_dirty_bitmap_enabled(BdrvDirtyBitmap *bitmap)
+{
+    return !(bitmap->disabled || bitmap->successor);
+}
+
+DirtyBitmapStatus bdrv_dirty_bitmap_status(BdrvDirtyBitmap *bitmap)
+{
+    if (bdrv_dirty_bitmap_frozen(bitmap)) {
+        return DIRTY_BITMAP_STATUS_FROZEN;
+    } else if (!bdrv_dirty_bitmap_enabled(bitmap)) {
+        return DIRTY_BITMAP_STATUS_DISABLED;
+    } else {
+        return DIRTY_BITMAP_STATUS_ACTIVE;
+    }
+}
+
+/**
+ * Create a successor bitmap destined to replace this bitmap after an operation.
+ * Requires that the bitmap is not frozen and has no successor.
+ */
+int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
+                                       BdrvDirtyBitmap *bitmap, Error **errp)
+{
+    uint64_t granularity;
+    BdrvDirtyBitmap *child;
+
+    if (bdrv_dirty_bitmap_frozen(bitmap)) {
+        error_setg(errp, "Cannot create a successor for a bitmap that is "
+                   "currently frozen");
+        return -1;
+    }
+    assert(!bitmap->successor);
+
+    /* Create an anonymous successor */
+    granularity = bdrv_dirty_bitmap_granularity(bitmap);
+    child = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
+    if (!child) {
+        return -1;
+    }
+
+    /* Successor will be on or off based on our current state. */
+    child->disabled = bitmap->disabled;
+
+    /* Install the successor and freeze the parent */
+    bitmap->successor = child;
+    return 0;
+}
+
+/**
+ * For a bitmap with a successor, yield our name to the successor,
+ * delete the old bitmap, and return a handle to the new bitmap.
+ */
+BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
+                                            BdrvDirtyBitmap *bitmap,
+                                            Error **errp)
+{
+    char *name;
+    BdrvDirtyBitmap *successor = bitmap->successor;
+
+    if (successor == NULL) {
+        error_setg(errp, "Cannot relinquish control if "
+                   "there's no successor present");
+        return NULL;
+    }
+
+    name = bitmap->name;
+    bitmap->name = NULL;
+    successor->name = name;
+    bitmap->successor = NULL;
+    bdrv_release_dirty_bitmap(bs, bitmap);
+
+    return successor;
+}
+
+/**
+ * In cases of failure where we can no longer safely delete the parent,
+ * we may wish to re-join the parent and child/successor.
+ * The merged parent will be un-frozen, but not explicitly re-enabled.
+ */
+BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState *bs,
+                                           BdrvDirtyBitmap *parent,
+                                           Error **errp)
+{
+    BdrvDirtyBitmap *successor = parent->successor;
+
+    if (!successor) {
+        error_setg(errp, "Cannot reclaim a successor when none is present");
+        return NULL;
+    }
+
+    if (!hbitmap_merge(parent->bitmap, successor->bitmap)) {
+        error_setg(errp, "Merging of parent and successor bitmap failed");
+        return NULL;
+    }
+    bdrv_release_dirty_bitmap(bs, successor);
+    parent->successor = NULL;
+
+    return parent;
+}
+
+/**
+ * Truncates _all_ bitmaps attached to a BDS.
+ */
+static void bdrv_dirty_bitmap_truncate(BlockDriverState *bs)
+{
+    BdrvDirtyBitmap *bitmap;
+    uint64_t size = bdrv_nb_sectors(bs);
+
+    QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
+        assert(!bdrv_dirty_bitmap_frozen(bitmap));
+        hbitmap_truncate(bitmap->bitmap, size);
+        bitmap->size = size;
+    }
+}
+
+void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap)
+{
+    BdrvDirtyBitmap *bm, *next;
+    QLIST_FOREACH_SAFE(bm, &bs->dirty_bitmaps, list, next) {
+        if (bm == bitmap) {
+            assert(!bdrv_dirty_bitmap_frozen(bm));
+            QLIST_REMOVE(bitmap, list);
+            hbitmap_free(bitmap->bitmap);
+            g_free(bitmap->name);
+            g_free(bitmap);
+            return;
+        }
+    }
+}
+
+void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
+{
+    assert(!bdrv_dirty_bitmap_frozen(bitmap));
+    bitmap->disabled = true;
+}
+
+void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
+{
+    assert(!bdrv_dirty_bitmap_frozen(bitmap));
+    bitmap->disabled = false;
+}
+
+BlockDirtyInfoList *bdrv_query_dirty_bitmaps(BlockDriverState *bs)
+{
+    BdrvDirtyBitmap *bm;
+    BlockDirtyInfoList *list = NULL;
+    BlockDirtyInfoList **plist = &list;
+
+    QLIST_FOREACH(bm, &bs->dirty_bitmaps, list) {
+        BlockDirtyInfo *info = g_new0(BlockDirtyInfo, 1);
+        BlockDirtyInfoList *entry = g_new0(BlockDirtyInfoList, 1);
+        info->count = bdrv_get_dirty_count(bm);
+        info->granularity = bdrv_dirty_bitmap_granularity(bm);
+        info->has_name = !!bm->name;
+        info->name = g_strdup(bm->name);
+        info->status = bdrv_dirty_bitmap_status(bm);
+        entry->value = info;
+        *plist = entry;
+        plist = &entry->next;
+    }
+
+    return list;
+}
+
+int bdrv_get_dirty(BlockDriverState *bs, BdrvDirtyBitmap *bitmap, int64_t sector)
+{
+    if (bitmap) {
+        return hbitmap_get(bitmap->bitmap, sector);
+    } else {
+        return 0;
+    }
+}
+
+/**
+ * Chooses a default granularity based on the existing cluster size,
+ * but clamped between [4K, 64K]. Defaults to 64K in the case that there
+ * is no cluster size information available.
+ */
+uint32_t bdrv_get_default_bitmap_granularity(BlockDriverState *bs)
+{
+    BlockDriverInfo bdi;
+    uint32_t granularity;
+
+    if (bdrv_get_info(bs, &bdi) >= 0 && bdi.cluster_size > 0) {
+        granularity = MAX(4096, bdi.cluster_size);
+        granularity = MIN(65536, granularity);
+    } else {
+        granularity = 65536;
+    }
+
+    return granularity;
+}
+
+uint32_t bdrv_dirty_bitmap_granularity(BdrvDirtyBitmap *bitmap)
+{
+    return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->bitmap);
+}
+
+void bdrv_dirty_iter_init(BdrvDirtyBitmap *bitmap, HBitmapIter *hbi)
+{
+    hbitmap_iter_init(hbi, bitmap->bitmap, 0);
+}
+
+void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
+                           int64_t cur_sector, int nr_sectors)
+{
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
+}
+
+void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
+                             int64_t cur_sector, int nr_sectors)
+{
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
+}
+
+void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out)
+{
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    if (!out) {
+        hbitmap_reset_all(bitmap->bitmap);
+    } else {
+        HBitmap *backup = bitmap->bitmap;
+        bitmap->bitmap = hbitmap_alloc(bitmap->size,
+                                       hbitmap_granularity(backup));
+        *out = backup;
+    }
+}
+
+void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *in)
+{
+    HBitmap *tmp = bitmap->bitmap;
+    assert(bdrv_dirty_bitmap_enabled(bitmap));
+    bitmap->bitmap = in;
+    hbitmap_free(tmp);
+}
+
+void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
+                    int nr_sectors)
+{
+    BdrvDirtyBitmap *bitmap;
+    QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
+        if (!bdrv_dirty_bitmap_enabled(bitmap)) {
+            continue;
+        }
+        hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
+    }
+}
+
+/**
+ * Advance an HBitmapIter to an arbitrary offset.
+ */
+void bdrv_set_dirty_iter(HBitmapIter *hbi, int64_t offset)
+{
+    assert(hbi->hb);
+    hbitmap_iter_init(hbi, hbi->hb, offset);
+}
+
+int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap)
+{
+    return hbitmap_count(bitmap->bitmap);
+}
+
+/* Get a reference to bs */
+void bdrv_ref(BlockDriverState *bs)
+{
+    bs->refcnt++;
+}
+
+/* Release a previously grabbed reference to bs.
+ * If after releasing, reference count is zero, the BlockDriverState is
+ * deleted. */
+void bdrv_unref(BlockDriverState *bs)
+{
+    if (!bs) {
+        return;
+    }
+    assert(bs->refcnt > 0);
+    if (--bs->refcnt == 0) {
+        bdrv_delete(bs);
+    }
+}
+
+struct BdrvOpBlocker {
+    Error *reason;
+    QLIST_ENTRY(BdrvOpBlocker) list;
+};
+
+bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp)
+{
+    BdrvOpBlocker *blocker;
+    assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
+    if (!QLIST_EMPTY(&bs->op_blockers[op])) {
+        blocker = QLIST_FIRST(&bs->op_blockers[op]);
+        if (errp) {
+            error_setg(errp, "Node '%s' is busy: %s",
+                       bdrv_get_device_or_node_name(bs),
+                       error_get_pretty(blocker->reason));
+        }
+        return true;
+    }
+    return false;
+}
+
+void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason)
+{
+    BdrvOpBlocker *blocker;
+    assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
+
+    blocker = g_new0(BdrvOpBlocker, 1);
+    blocker->reason = reason;
+    QLIST_INSERT_HEAD(&bs->op_blockers[op], blocker, list);
+}
+
+void bdrv_op_unblock(BlockDriverState *bs, BlockOpType op, Error *reason)
+{
+    BdrvOpBlocker *blocker, *next;
+    assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
+    QLIST_FOREACH_SAFE(blocker, &bs->op_blockers[op], list, next) {
+        if (blocker->reason == reason) {
+            QLIST_REMOVE(blocker, list);
+            g_free(blocker);
+        }
+    }
+}
+
+void bdrv_op_block_all(BlockDriverState *bs, Error *reason)
+{
+    int i;
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        bdrv_op_block(bs, i, reason);
+    }
+}
+
+void bdrv_op_unblock_all(BlockDriverState *bs, Error *reason)
+{
+    int i;
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        bdrv_op_unblock(bs, i, reason);
+    }
+}
+
+bool bdrv_op_blocker_is_empty(BlockDriverState *bs)
+{
+    int i;
+
+    for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
+        if (!QLIST_EMPTY(&bs->op_blockers[i])) {
+            return false;
+        }
+    }
+    return true;
+}
+
+void bdrv_img_create(const char *filename, const char *fmt,
+                     const char *base_filename, const char *base_fmt,
+                     char *options, uint64_t img_size, int flags,
+                     Error **errp, bool quiet)
+{
+    QemuOptsList *create_opts = NULL;
+    QemuOpts *opts = NULL;
+    const char *backing_fmt, *backing_file;
+    int64_t size;
+    BlockDriver *drv, *proto_drv;
+    Error *local_err = NULL;
+    int ret = 0;
+
+    /* Find driver and parse its options */
+    drv = bdrv_find_format(fmt);
+    if (!drv) {
+        error_setg(errp, "Unknown file format '%s'", fmt);
+        return;
+    }
+
+    proto_drv = bdrv_find_protocol(filename, true, errp);
+    if (!proto_drv) {
+        return;
+    }
+
+    if (!drv->create_opts) {
+        error_setg(errp, "Format driver '%s' does not support image creation",
+                   drv->format_name);
+        return;
+    }
+
+    if (!proto_drv->create_opts) {
+        error_setg(errp, "Protocol driver '%s' does not support image creation",
+                   proto_drv->format_name);
+        return;
+    }
+
+    create_opts = qemu_opts_append(create_opts, drv->create_opts);
+    create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
+
+    /* Create parameter list with default values */
+    opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
+    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
+
+    /* Parse -o options */
+    if (options) {
+        qemu_opts_do_parse(opts, options, NULL, &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+            local_err = NULL;
+            error_setg(errp, "Invalid options for file format '%s'", fmt);
+            goto out;
+        }
+    }
+
+    if (base_filename) {
+        qemu_opt_set(opts, BLOCK_OPT_BACKING_FILE, base_filename, &local_err);
+        if (local_err) {
+            error_setg(errp, "Backing file not supported for file format '%s'",
+                       fmt);
+            goto out;
+        }
+    }
+
+    if (base_fmt) {
+        qemu_opt_set(opts, BLOCK_OPT_BACKING_FMT, base_fmt, &local_err);
+        if (local_err) {
+            error_setg(errp, "Backing file format not supported for file "
+                             "format '%s'", fmt);
+            goto out;
+        }
+    }
+
+    backing_file = qemu_opt_get(opts, BLOCK_OPT_BACKING_FILE);
+    if (backing_file) {
+        if (!strcmp(filename, backing_file)) {
+            error_setg(errp, "Error: Trying to create an image with the "
+                             "same filename as the backing file");
+            goto out;
+        }
+    }
+
+    backing_fmt = qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT);
+
+    // 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
+    size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 0);
+    if (size == -1) {
+        if (backing_file) {
+            BlockDriverState *bs;
+            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,
+                                                         &local_err);
+            if (local_err) {
+                g_free(full_backing);
+                goto out;
+            }
+
+            /* backing files always opened read-only */
+            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, backing_options,
+                            back_flags, &local_err);
+            g_free(full_backing);
+            if (ret < 0) {
+                goto out;
+            }
+            size = bdrv_getlength(bs);
+            if (size < 0) {
+                error_setg_errno(errp, -size, "Could not get size of '%s'",
+                                 backing_file);
+                bdrv_unref(bs);
+                goto out;
+            }
+
+            qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
+
+            bdrv_unref(bs);
+        } else {
+            error_setg(errp, "Image creation needs a size parameter");
+            goto out;
+        }
+    }
+
+    if (!quiet) {
+        printf("Formatting '%s', fmt=%s ", filename, fmt);
+        qemu_opts_print(opts, " ");
+        puts("");
+    }
+
+    ret = bdrv_create(drv, filename, opts, &local_err);
+
+    if (ret == -EFBIG) {
+        /* This is generally a better message than whatever the driver would
+         * deliver (especially because of the cluster_size_hint), since that
+         * is most probably not much different from "image too large". */
+        const char *cluster_size_hint = "";
+        if (qemu_opt_get_size(opts, BLOCK_OPT_CLUSTER_SIZE, 0)) {
+            cluster_size_hint = " (try using a larger cluster size)";
+        }
+        error_setg(errp, "The image size is too large for file format '%s'"
+                   "%s", fmt, cluster_size_hint);
+        error_free(local_err);
+        local_err = NULL;
+    }
+
+out:
+    qemu_opts_del(opts);
+    qemu_opts_free(create_opts);
+    if (local_err) {
+        error_propagate(errp, local_err);
+    }
+}
+
+AioContext *bdrv_get_aio_context(BlockDriverState *bs)
+{
+    return bs->aio_context;
+}
+
+void bdrv_detach_aio_context(BlockDriverState *bs)
+{
+    BdrvAioNotifier *baf;
+
+    if (!bs->drv) {
+        return;
+    }
+
+    QLIST_FOREACH(baf, &bs->aio_notifiers, list) {
+        baf->detach_aio_context(baf->opaque);
+    }
+
+    if (bs->throttle_state) {
+        throttle_timers_detach_aio_context(&bs->throttle_timers);
+    }
+    if (bs->drv->bdrv_detach_aio_context) {
+        bs->drv->bdrv_detach_aio_context(bs);
+    }
+    if (bs->file) {
+        bdrv_detach_aio_context(bs->file->bs);
+    }
+    if (bs->backing) {
+        bdrv_detach_aio_context(bs->backing->bs);
+    }
+
+    bs->aio_context = NULL;
+}
+
+void bdrv_attach_aio_context(BlockDriverState *bs,
+                             AioContext *new_context)
+{
+    BdrvAioNotifier *ban;
+
+    if (!bs->drv) {
+        return;
+    }
+
+    bs->aio_context = new_context;
+
+    if (bs->backing) {
+        bdrv_attach_aio_context(bs->backing->bs, new_context);
+    }
+    if (bs->file) {
+        bdrv_attach_aio_context(bs->file->bs, new_context);
+    }
+    if (bs->drv->bdrv_attach_aio_context) {
+        bs->drv->bdrv_attach_aio_context(bs, new_context);
+    }
+    if (bs->throttle_state) {
+        throttle_timers_attach_aio_context(&bs->throttle_timers, new_context);
+    }
+
+    QLIST_FOREACH(ban, &bs->aio_notifiers, list) {
+        ban->attached_aio_context(new_context, ban->opaque);
+    }
+}
+
+void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
+{
+    bdrv_drain(bs); /* ensure there are no in-flight requests */
+
+    bdrv_detach_aio_context(bs);
+
+    /* This function executes in the old AioContext so acquire the new one in
+     * case it runs in a different thread.
+     */
+    aio_context_acquire(new_context);
+    bdrv_attach_aio_context(bs, new_context);
+    aio_context_release(new_context);
+}
+
+void bdrv_add_aio_context_notifier(BlockDriverState *bs,
+        void (*attached_aio_context)(AioContext *new_context, void *opaque),
+        void (*detach_aio_context)(void *opaque), void *opaque)
+{
+    BdrvAioNotifier *ban = g_new(BdrvAioNotifier, 1);
+    *ban = (BdrvAioNotifier){
+        .attached_aio_context = attached_aio_context,
+        .detach_aio_context   = detach_aio_context,
+        .opaque               = opaque
+    };
+
+    QLIST_INSERT_HEAD(&bs->aio_notifiers, ban, list);
+}
+
+void bdrv_remove_aio_context_notifier(BlockDriverState *bs,
+                                      void (*attached_aio_context)(AioContext *,
+                                                                   void *),
+                                      void (*detach_aio_context)(void *),
+                                      void *opaque)
+{
+    BdrvAioNotifier *ban, *ban_next;
+
+    QLIST_FOREACH_SAFE(ban, &bs->aio_notifiers, list, ban_next) {
+        if (ban->attached_aio_context == attached_aio_context &&
+            ban->detach_aio_context   == detach_aio_context   &&
+            ban->opaque               == opaque)
+        {
+            QLIST_REMOVE(ban, list);
+            g_free(ban);
+
+            return;
+        }
+    }
+
+    abort();
+}
+
+int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
+                       BlockDriverAmendStatusCB *status_cb)
+{
+    if (!bs->drv->bdrv_amend_options) {
+        return -ENOTSUP;
+    }
+    return bs->drv->bdrv_amend_options(bs, opts, status_cb);
+}
+
+/* This function will be called by the bdrv_recurse_is_first_non_filter method
+ * of block filter and by bdrv_is_first_non_filter.
+ * It is used to test if the given bs is the candidate or recurse more in the
+ * node graph.
+ */
+bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
+                                      BlockDriverState *candidate)
+{
+    /* return false if basic checks fails */
+    if (!bs || !bs->drv) {
+        return false;
+    }
+
+    /* the code reached a non block filter driver -> check if the bs is
+     * the same as the candidate. It's the recursion termination condition.
+     */
+    if (!bs->drv->is_filter) {
+        return bs == candidate;
+    }
+    /* Down this path the driver is a block filter driver */
+
+    /* If the block filter recursion method is defined use it to recurse down
+     * the node graph.
+     */
+    if (bs->drv->bdrv_recurse_is_first_non_filter) {
+        return bs->drv->bdrv_recurse_is_first_non_filter(bs, candidate);
+    }
+
+    /* the driver is a block filter but don't allow to recurse -> return false
+     */
+    return false;
+}
+
+/* This function checks if the candidate is the first non filter bs down it's
+ * bs chain. Since we don't have pointers to parents it explore all bs chains
+ * from the top. Some filters can choose not to pass down the recursion.
+ */
+bool bdrv_is_first_non_filter(BlockDriverState *candidate)
+{
+    BlockDriverState *bs;
+
+    /* walk down the bs forest recursively */
+    QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        bool perm;
+
+        /* try to recurse in this top level bs */
+        perm = bdrv_recurse_is_first_non_filter(bs, candidate);
+
+        /* candidate is the first non filter */
+        if (perm) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
+                                        const char *node_name, Error **errp)
+{
+    BlockDriverState *to_replace_bs = bdrv_find_node(node_name);
+    AioContext *aio_context;
+
+    if (!to_replace_bs) {
+        error_setg(errp, "Node name '%s' not found", node_name);
+        return NULL;
+    }
+
+    aio_context = bdrv_get_aio_context(to_replace_bs);
+    aio_context_acquire(aio_context);
+
+    if (bdrv_op_is_blocked(to_replace_bs, BLOCK_OP_TYPE_REPLACE, errp)) {
+        to_replace_bs = NULL;
+        goto out;
+    }
+
+    /* We don't want arbitrary node of the BDS chain to be replaced only the top
+     * most non filter in order to prevent data corruption.
+     * Another benefit is that this tests exclude backing files which are
+     * blocked by the backing blockers.
+     */
+    if (!bdrv_recurse_is_first_non_filter(parent_bs, to_replace_bs)) {
+        error_setg(errp, "Only top most non filter can be replaced");
+        to_replace_bs = NULL;
+        goto out;
+    }
+
+out:
+    aio_context_release(aio_context);
+    return to_replace_bs;
+}
+
+static bool append_open_options(QDict *d, BlockDriverState *bs)
+{
+    const QDictEntry *entry;
+    bool found_any = false;
+
+    for (entry = qdict_first(bs->options); entry;
+         entry = qdict_next(bs->options, entry))
+    {
+        /* Only take options for this level and exclude all non-driver-specific
+         * options */
+        if (!strchr(qdict_entry_key(entry), '.') &&
+            strcmp(qdict_entry_key(entry), "node-name"))
+        {
+            qobject_incref(qdict_entry_value(entry));
+            qdict_put_obj(d, qdict_entry_key(entry), qdict_entry_value(entry));
+            found_any = true;
+        }
+    }
+
+    return found_any;
+}
+
+/* Updates the following BDS fields:
+ *  - exact_filename: A filename which may be used for opening a block device
+ *                    which (mostly) equals the given BDS (even without any
+ *                    other options; so reading and writing must return the same
+ *                    results, but caching etc. may be different)
+ *  - full_open_options: Options which, when given when opening a block device
+ *                       (without a filename), result in a BDS (mostly)
+ *                       equalling the given one
+ *  - filename: If exact_filename is set, it is copied here. Otherwise,
+ *              full_open_options is converted to a JSON object, prefixed with
+ *              "json:" (for use through the JSON pseudo protocol) and put here.
+ */
+void bdrv_refresh_filename(BlockDriverState *bs)
+{
+    BlockDriver *drv = bs->drv;
+    QDict *opts;
+
+    if (!drv) {
+        return;
+    }
+
+    /* This BDS's file name will most probably depend on its file's name, so
+     * refresh that first */
+    if (bs->file) {
+        bdrv_refresh_filename(bs->file->bs);
+    }
+
+    if (drv->bdrv_refresh_filename) {
+        /* Obsolete information is of no use here, so drop the old file name
+         * information before refreshing it */
+        bs->exact_filename[0] = '\0';
+        if (bs->full_open_options) {
+            QDECREF(bs->full_open_options);
+            bs->full_open_options = NULL;
+        }
+
+        drv->bdrv_refresh_filename(bs);
+    } else if (bs->file) {
+        /* Try to reconstruct valid information from the underlying file */
+        bool has_open_options;
+
+        bs->exact_filename[0] = '\0';
+        if (bs->full_open_options) {
+            QDECREF(bs->full_open_options);
+            bs->full_open_options = NULL;
+        }
+
+        opts = qdict_new();
+        has_open_options = append_open_options(opts, bs);
+
+        /* If no specific options have been given for this BDS, the filename of
+         * the underlying file should suffice for this one as well */
+        if (bs->file->bs->exact_filename[0] && !has_open_options) {
+            strcpy(bs->exact_filename, bs->file->bs->exact_filename);
+        }
+        /* Reconstructing the full options QDict is simple for most format block
+         * drivers, as long as the full options are known for the underlying
+         * file BDS. The full options QDict of that file BDS should somehow
+         * contain a representation of the filename, therefore the following
+         * suffices without querying the (exact_)filename of this BDS. */
+        if (bs->file->bs->full_open_options) {
+            qdict_put_obj(opts, "driver",
+                          QOBJECT(qstring_from_str(drv->format_name)));
+            QINCREF(bs->file->bs->full_open_options);
+            qdict_put_obj(opts, "file",
+                          QOBJECT(bs->file->bs->full_open_options));
+
+            bs->full_open_options = opts;
+        } else {
+            QDECREF(opts);
+        }
+    } else if (!bs->full_open_options && qdict_size(bs->options)) {
+        /* There is no underlying file BDS (at least referenced by BDS.file),
+         * so the full options QDict should be equal to the options given
+         * specifically for this block device when it was opened (plus the
+         * driver specification).
+         * Because those options don't change, there is no need to update
+         * full_open_options when it's already set. */
+
+        opts = qdict_new();
+        append_open_options(opts, bs);
+        qdict_put_obj(opts, "driver",
+                      QOBJECT(qstring_from_str(drv->format_name)));
+
+        if (bs->exact_filename[0]) {
+            /* This may not work for all block protocol drivers (some may
+             * require this filename to be parsed), but we have to find some
+             * default solution here, so just include it. If some block driver
+             * does not support pure options without any filename at all or
+             * needs some special format of the options QDict, it needs to
+             * implement the driver-specific bdrv_refresh_filename() function.
+             */
+            qdict_put_obj(opts, "filename",
+                          QOBJECT(qstring_from_str(bs->exact_filename)));
+        }
+
+        bs->full_open_options = opts;
+    }
+
+    if (bs->exact_filename[0]) {
+        pstrcpy(bs->filename, sizeof(bs->filename), bs->exact_filename);
+    } else if (bs->full_open_options) {
+        QString *json = qobject_to_json(QOBJECT(bs->full_open_options));
+        snprintf(bs->filename, sizeof(bs->filename), "json:%s",
+                 qstring_get_str(json));
+        QDECREF(json);
+    }
+}