Patchwork [3/5] introduce new vma archive format

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Submitter Dietmar Maurer
Date Nov. 21, 2012, 9:01 a.m.
Message ID <1353488464-82756-3-git-send-email-dietmar@proxmox.com>
Download mbox | patch
Permalink /patch/200612/
State New
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Comments

Dietmar Maurer - Nov. 21, 2012, 9:01 a.m.
This is a very simple archive format, see docs/specs/vma_spec.txt

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
---
 Makefile                |    3 +-
 docs/specs/vma_spec.txt |   24 ++
 vma-reader.c            |  720 +++++++++++++++++++++++++++++++++++++++++
 vma-writer.c            |  824 +++++++++++++++++++++++++++++++++++++++++++++++
 vma.c                   |  526 ++++++++++++++++++++++++++++++
 vma.h                   |  139 ++++++++
 6 files changed, 2235 insertions(+), 1 deletions(-)
 create mode 100644 docs/specs/vma_spec.txt
 create mode 100644 vma-reader.c
 create mode 100644 vma-writer.c
 create mode 100644 vma.c
 create mode 100644 vma.h
Eric Blake - Nov. 21, 2012, 4:06 p.m.
On 11/21/2012 02:01 AM, Dietmar Maurer wrote:
> This is a very simple archive format, see docs/specs/vma_spec.txt
> 
> Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
> ---

> +++ b/docs/specs/vma_spec.txt
> @@ -0,0 +1,24 @@
> +=Virtual Machine Archive format (VMA)=
> +
> +This format contains a header which includes the VM configuration as
> +binary blobs, and a list of devices (dev_id, name).
> +
> +The actual VM image date is stored inside extends. En extend contains

s/date/data/
s/extends. En extend/extents. An extent/

> +up to 64 clusters, and start with a 512 byte header containing
> +additional information for those clusters.
> +
> +We use a cluster size of 65536, and use 8 bytes for each
> +cluster in the header to store the following information:
> +
> +* 1 byte dev_id (to identity the drive)
> +* 2 bytes zero indicator (mark zero regions (16x4069))

s/4069/4096/

> +* 4 bytes cluster number

Is that sufficient, or is it possible to have an image larger than
64k*4G that would overflow?

> +* 1 byte not used (reserved)
> +
> +We only store non-zero blocks (such block is 4096 bytes).
> +
> +Each archive is marked with an unique uuid. The archive header and all

s/an unique/a/ (by definition, 'uuid' is an acronym that already means
unique; also, it is 'a' and not 'an' before any 'u' pronounced as 'y',
which is true for both 'unique' and a spelled-out 'uuid')

> +extend headers includes that uuid and a MD5 checksum (over header

s/extend/extent/

> +data).
> +
> +
> diff --git a/vma-reader.c b/vma-reader.c
> new file mode 100644
> index 0000000..7a54de5
> --- /dev/null
> +++ b/vma-reader.c
> @@ -0,0 +1,720 @@
> +/*
> + * VMA: Virtual Machine Archive
> + *
> + * Copyright (C) Proxmox Server Solutions

Missing a year.

> + *
> + * Authors:
> + *  Dietmar Maurer (dietmar@proxmox.com)
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See

Can you please use GPLv2+ (the 'or later' clause is essential if you
want your work to be reusable in GPLv3[+] projects)?

I didn't review the code, just the specification.  I have to wonder how
much of your work overlaps with Paolo's 'drive-mirror' and NBD server
work; and it seems to me that it is better to use 'drive-mirror' for
doing backup work into existing disk formats, rather than inventing yet
another archive format.
Dietmar Maurer - Nov. 21, 2012, 5:56 p.m.
> > +* 4 bytes cluster number

> 

> Is that sufficient, or is it possible to have an image larger than 64k*4G that

> would overflow?


Well, that is 256TB per image. This is sufficient for us.

> > +* 1 byte not used (reserved)

> > +

> > +We only store non-zero blocks (such block is 4096 bytes).

> > +

> > +Each archive is marked with an unique uuid. The archive header and

> > +all

> 

> s/an unique/a/ (by definition, 'uuid' is an acronym that already means

> unique; also, it is 'a' and not 'an' before any 'u' pronounced as 'y', which is

> true for both 'unique' and a spelled-out 'uuid')


many thanks for your help - will fix those things.

> > + * This work is licensed under the terms of the GNU GPL, version 2.

> > + See

> 

> Can you please use GPLv2+ (the 'or later' clause is essential if you want your

> work to be reusable in GPLv3[+] projects)?


sure, no problem.
 
> I didn't review the code, just the specification.  I have to wonder how much

> of your work overlaps with Paolo's 'drive-mirror' and NBD server work; and it

> seems to me that it is better to use 'drive-mirror' for doing backup work into

> existing disk formats, rather than inventing yet another archive format.


I already tried to explain why that does not work - see my previous posts.

What image format provides that functionality?

Patch

diff --git a/Makefile b/Makefile
index 3e8d441..3433dc2 100644
--- a/Makefile
+++ b/Makefile
@@ -100,7 +100,7 @@  defconfig:
 
 -include config-all-devices.mak
 
-all: $(DOCS) $(TOOLS) $(HELPERS-y) recurse-all
+all: $(DOCS) $(TOOLS) vma$(EXESUF) $(HELPERS-y) recurse-all
 
 config-host.h: config-host.h-timestamp
 config-host.h-timestamp: config-host.mak
@@ -194,6 +194,7 @@  tools-obj-$(CONFIG_POSIX) += compatfd.o
 qemu-img$(EXESUF): qemu-img.o $(tools-obj-y) $(block-obj-y) libqemustub.a
 qemu-nbd$(EXESUF): qemu-nbd.o $(tools-obj-y) $(block-obj-y) libqemustub.a
 qemu-io$(EXESUF): qemu-io.o cmd.o $(tools-obj-y) $(block-obj-y) libqemustub.a
+vma$(EXESUF): vma.o vma-writer.o vma-reader.o $(tools-obj-y) $(block-obj-y) libqemustub.a
 
 qemu-bridge-helper$(EXESUF): qemu-bridge-helper.o
 
diff --git a/docs/specs/vma_spec.txt b/docs/specs/vma_spec.txt
new file mode 100644
index 0000000..28eb292
--- /dev/null
+++ b/docs/specs/vma_spec.txt
@@ -0,0 +1,24 @@ 
+=Virtual Machine Archive format (VMA)=
+
+This format contains a header which includes the VM configuration as
+binary blobs, and a list of devices (dev_id, name).
+
+The actual VM image date is stored inside extends. En extend contains
+up to 64 clusters, and start with a 512 byte header containing
+additional information for those clusters.
+
+We use a cluster size of 65536, and use 8 bytes for each
+cluster in the header to store the following information:
+
+* 1 byte dev_id (to identity the drive)
+* 2 bytes zero indicator (mark zero regions (16x4069))
+* 4 bytes cluster number
+* 1 byte not used (reserved)
+
+We only store non-zero blocks (such block is 4096 bytes).
+
+Each archive is marked with an unique uuid. The archive header and all
+extend headers includes that uuid and a MD5 checksum (over header
+data).
+
+
diff --git a/vma-reader.c b/vma-reader.c
new file mode 100644
index 0000000..7a54de5
--- /dev/null
+++ b/vma-reader.c
@@ -0,0 +1,720 @@ 
+/*
+ * VMA: Virtual Machine Archive
+ *
+ * Copyright (C) Proxmox Server Solutions
+ *
+ * Authors:
+ *  Dietmar Maurer (dietmar@proxmox.com)
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <glib.h>
+#include <uuid/uuid.h>
+
+#include "qemu-common.h"
+#include "qemu_socket.h"
+#include "qemu-coroutine.h"
+#include "qemu-aio.h"
+#include "qemu/ratelimit.h"
+#include "vma.h"
+#include "block.h"
+
+/* TODO:
+
+   check if we restored all data (use bitmaps?)
+
+ */
+
+#define BITS_PER_LONG  (sizeof(unsigned long) * 8)
+
+static unsigned char zero_vma_block[VMA_BLOCK_SIZE];
+
+typedef struct VmaRestoreState {
+    BlockDriverState *bs;
+    bool write_zeroes;
+    unsigned long *bitmap;
+    int bitmap_size;
+}  VmaRestoreState;
+
+struct VmaReader {
+    int fd;
+    GChecksum *md5csum;
+    GHashTable *blob_hash;
+    unsigned char *head_data;
+    VmaDeviceInfo devinfo[256];
+    VmaRestoreState rstate[256];
+    GList *cdata_list;
+};
+
+static guint
+g_int32_hash(gconstpointer v)
+{
+    return *(const uint32_t *)v;
+}
+
+static gboolean
+g_int32_equal(gconstpointer v1, gconstpointer v2)
+{
+    return *((const uint32_t *)v1) == *((const uint32_t *)v2);
+}
+
+static int vma_reader_get_bitmap(VmaRestoreState *rstate, int64_t cluster_num)
+{
+    assert(rstate);
+    assert(rstate->bitmap);
+
+    unsigned long val, idx, bit;
+
+    idx = cluster_num / BITS_PER_LONG;
+
+    assert(rstate->bitmap_size > idx);
+
+    bit = cluster_num % BITS_PER_LONG;
+    val = rstate->bitmap[idx];
+
+    return !!(val & (1UL << bit));
+}
+
+static void vma_reader_set_bitmap(VmaRestoreState *rstate, int64_t cluster_num,
+                                  int dirty)
+{
+    assert(rstate);
+    assert(rstate->bitmap);
+
+    unsigned long val, idx, bit;
+
+    idx = cluster_num / BITS_PER_LONG;
+
+    assert(rstate->bitmap_size > idx);
+
+    bit = cluster_num % BITS_PER_LONG;
+    val = rstate->bitmap[idx];
+    if (dirty) {
+        if (!(val & (1UL << bit))) {
+            val |= 1UL << bit;
+        }
+    } else {
+        if (val & (1UL << bit)) {
+            val &= ~(1UL << bit);
+        }
+    }
+    rstate->bitmap[idx] = val;
+}
+
+typedef struct VmaBlob {
+    uint32_t start;
+    uint32_t len;
+    unsigned char *data;
+} VmaBlob;
+
+static const VmaBlob *get_header_blob(VmaReader *vmar, uint32_t pos)
+{
+    assert(vmar);
+    assert(vmar->blob_hash);
+
+    return g_hash_table_lookup(vmar->blob_hash, &pos);
+}
+
+static const unsigned char *get_header_str(VmaReader *vmar, uint32_t pos)
+{
+    const VmaBlob *blob = get_header_blob(vmar, pos);
+    if (!blob || (blob->data[blob->len-1] != '\0')) {
+        return NULL;
+    }
+    return blob->data;
+}
+
+static ssize_t
+safe_read(int fd, unsigned char *buf, size_t count)
+{
+    ssize_t n;
+
+    do {
+        n = read(fd, buf, count);
+    } while (n < 0 && errno == EINTR);
+
+    return n;
+}
+
+static ssize_t
+full_read(int fd, unsigned char *buf, size_t len)
+{
+    ssize_t n;
+    size_t total;
+
+    total = 0;
+
+    while (len > 0) {
+        n = safe_read(fd, buf, len);
+
+        if (n == 0) {
+            return total;
+        }
+
+        if (n <= 0) {
+            break;
+        }
+
+        buf += n;
+        total += n;
+        len -= n;
+    }
+
+    if (len) {
+        return -1;
+    }
+
+    return total;
+}
+
+void vma_reader_destroy(VmaReader *vmar)
+{
+    assert(vmar);
+
+    if (vmar->fd >= 0) {
+        close(vmar->fd);
+    }
+
+    if (vmar->cdata_list) {
+        g_list_free(vmar->cdata_list);
+    }
+
+    int i;
+    for (i = 1; i < 256; i++) {
+        if (vmar->rstate[i].bitmap) {
+            g_free(vmar->rstate[i].bitmap);
+        }
+    }
+
+    if (vmar->md5csum) {
+        g_checksum_free(vmar->md5csum);
+    }
+
+    if (vmar->blob_hash) {
+        g_hash_table_destroy(vmar->blob_hash);
+    }
+
+    if (vmar->head_data) {
+        g_free(vmar->head_data);
+    }
+
+    g_free(vmar);
+
+};
+
+static int vma_reader_read_head(VmaReader *vmar, Error **errp)
+{
+    assert(vmar);
+    assert(errp);
+    assert(*errp == NULL);
+
+    unsigned char md5sum[16];
+    int i;
+    int ret = 0;
+
+    vmar->head_data = g_malloc(sizeof(VmaHeader));
+
+    if (full_read(vmar->fd, vmar->head_data, sizeof(VmaHeader)) !=
+        sizeof(VmaHeader)) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "can't read vma header - %s",
+                  errno ? strerror(errno) : "got EOF");
+        return -1;
+    }
+
+    VmaHeader *h = (VmaHeader *)vmar->head_data;
+
+    if (h->magic != VMA_MAGIC) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "not a vma file - wrong magic number");
+        return -1;
+    }
+
+    uint32_t header_size = GUINT32_FROM_BE(h->header_size);
+    int need = header_size - sizeof(VmaHeader);
+    if (need <= 0) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "wrong vma header size %d", header_size);
+        return -1;
+    }
+
+    vmar->head_data = g_realloc(vmar->head_data, header_size);
+    h = (VmaHeader *)vmar->head_data;
+
+    if (full_read(vmar->fd, vmar->head_data + sizeof(VmaHeader), need) !=
+        need) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "can't read vma header data - %s",
+                  errno ? strerror(errno) : "got EOF");
+        return -1;
+    }
+
+    memcpy(md5sum, h->md5sum, 16);
+    memset(h->md5sum, 0, 16);
+
+    g_checksum_reset(vmar->md5csum);
+    g_checksum_update(vmar->md5csum, vmar->head_data, header_size);
+    gsize csize = 16;
+    g_checksum_get_digest(vmar->md5csum, (guint8 *)(h->md5sum), &csize);
+
+    if (memcmp(md5sum, h->md5sum, 16) != 0) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR, "wrong vma header chechsum");
+        return -1;
+    }
+
+    /* we can modify header data after checksum verify */
+    h->header_size = header_size;
+
+    h->version = GUINT32_FROM_BE(h->version);
+    if (h->version != 1) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "wrong vma version %d", h->version);
+        return -1;
+    }
+
+    h->ctime = GUINT64_FROM_BE(h->ctime);
+    h->blob_buffer_offset = GUINT32_FROM_BE(h->blob_buffer_offset);
+    h->blob_buffer_size = GUINT32_FROM_BE(h->blob_buffer_size);
+
+    uint32_t bstart = h->blob_buffer_offset + 1;
+    uint32_t bend = h->blob_buffer_offset + h->blob_buffer_size;
+
+    if (bstart <= sizeof(VmaHeader)) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "wrong vma blob buffer offset %d", h->blob_buffer_offset);
+        return -1;
+    }
+
+    if (bend > header_size) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "wrong vma blob buffer size %d/%d", h->blob_buffer_offset,
+                  h->blob_buffer_size);
+        return -1;
+    }
+
+    while ((bstart + 2) <= bend) {
+        uint32_t size = vmar->head_data[bstart] +
+            (vmar->head_data[bstart+1] << 8);
+        if ((bstart + size + 2) <= bend) {
+            VmaBlob *blob = g_new0(VmaBlob, 1);
+            blob->start = bstart - h->blob_buffer_offset;
+            blob->len = size;
+            blob->data = vmar->head_data + bstart + 2;
+            g_hash_table_insert(vmar->blob_hash, &blob->start, blob);
+        }
+        bstart += size + 2;
+    }
+
+
+    int count = 0;
+    for (i = 1; i < 256; i++) {
+        VmaDeviceInfoHeader *dih = &h->dev_info[i];
+        uint32_t devname_ptr = GUINT32_FROM_BE(dih->devname_ptr);
+        uint64_t size = GUINT64_FROM_BE(dih->size);
+        const unsigned char *devname =  get_header_str(vmar, devname_ptr);
+
+        if (size && devname) {
+            count++;
+            vmar->devinfo[i].size = size;
+            vmar->devinfo[i].devname = devname;
+        }
+    }
+
+    if (!count) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR, "vma does not contain data");
+        return -1;
+    }
+
+    for (i = 0; i < VMA_MAX_CONFIGS; i++) {
+        uint32_t name_ptr = GUINT32_FROM_BE(h->config_names[i]);
+        uint32_t data_ptr = GUINT32_FROM_BE(h->config_data[i]);
+
+        if (!(name_ptr && data_ptr)) {
+            continue;
+        }
+        const unsigned char *name =  get_header_str(vmar, name_ptr);
+        const VmaBlob *blob = get_header_blob(vmar, data_ptr);
+
+        if (!(name && blob)) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "vma contains invalid data pointers");
+            return -1;
+        }
+
+        VmaConfigData *cdata = g_new0(VmaConfigData, 1);
+        cdata->name = name;
+        cdata->data = blob->data;
+        cdata->len = blob->len;
+
+        vmar->cdata_list = g_list_append(vmar->cdata_list, cdata);
+    }
+
+    return ret;
+};
+
+VmaReader *vma_reader_create(const char *filename, Error **errp)
+{
+    assert(filename);
+    assert(errp);
+
+    VmaReader *vmar = g_new0(VmaReader, 1);
+
+    vmar->fd = open(filename, O_RDONLY);
+
+    if (vmar->fd < 0) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "can't open file %s - %s\n", filename, strerror(errno));
+        goto err;
+    }
+
+    vmar->md5csum = g_checksum_new(G_CHECKSUM_MD5);
+    if (!vmar->md5csum) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "can't allocate cmsum\n");
+        goto err;
+    }
+
+    vmar->blob_hash = g_hash_table_new_full(g_int32_hash, g_int32_equal,
+                                            NULL, g_free);
+
+    if (vma_reader_read_head(vmar, errp) < 0) {
+        goto err;
+    }
+
+    return vmar;
+
+err:
+    if (vmar) {
+        vma_reader_destroy(vmar);
+    }
+
+    return NULL;
+}
+
+VmaHeader *vma_reader_get_header(VmaReader *vmar)
+{
+    assert(vmar);
+    assert(vmar->head_data);
+
+    return (VmaHeader *)(vmar->head_data);
+}
+
+GList *vma_reader_get_config_data(VmaReader *vmar)
+{
+    assert(vmar);
+    assert(vmar->head_data);
+
+    return vmar->cdata_list;
+}
+
+VmaDeviceInfo *vma_reader_get_device_info(VmaReader *vmar, guint8 dev_id)
+{
+    assert(vmar);
+    assert(dev_id);
+
+    if (vmar->devinfo[dev_id].size && vmar->devinfo[dev_id].devname) {
+        return &vmar->devinfo[dev_id];
+    }
+
+    return NULL;
+}
+
+int vma_reader_register_bs(VmaReader *vmar, guint8 dev_id, BlockDriverState *bs,
+                           bool write_zeroes, Error **errp)
+{
+    assert(vmar);
+    assert(bs != NULL);
+    assert(dev_id);
+    assert(vmar->rstate[dev_id].bs == NULL);
+
+    int64_t size = bdrv_getlength(bs);
+    if (size != vmar->devinfo[dev_id].size) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "vma_reader_register_bs for stream %s failed - "
+                  "unexpected size %zd != %zd", vmar->devinfo[dev_id].devname,
+                  size, vmar->devinfo[dev_id].size);
+        return -1;
+    }
+
+    vmar->rstate[dev_id].bs = bs;
+    vmar->rstate[dev_id].write_zeroes = write_zeroes;
+
+    int64_t bitmap_size = (size/BDRV_SECTOR_SIZE) +
+        (VMA_CLUSTER_SIZE/BDRV_SECTOR_SIZE) * BITS_PER_LONG - 1;
+    bitmap_size /= (VMA_CLUSTER_SIZE/BDRV_SECTOR_SIZE) * BITS_PER_LONG;
+
+    vmar->rstate[dev_id].bitmap_size = bitmap_size;
+    vmar->rstate[dev_id].bitmap = g_new0(unsigned long, bitmap_size);
+
+    return 0;
+}
+
+static int restore_extend(VmaReader *vmar, unsigned char *buf,
+                          int extend_size, Error **errp)
+{
+    assert(vmar);
+    assert(buf);
+
+    VmaExtendHeader *ehead = (VmaExtendHeader *)buf;
+    int start = VMA_EXTEND_HEADER_SIZE;
+    int i;
+
+    for (i = 0; i < VMA_BLOCKS_PER_EXTEND; i++) {
+        uint64_t block_info = GUINT64_FROM_BE(ehead->blockinfo[i]);
+        uint32_t cluster_num = block_info &  0xffffffff;
+        uint8_t dev_id = (block_info >> 32) &  0xff;
+        uint16_t mask = block_info >> (32+16);
+
+        if (!dev_id) {
+            continue;
+        }
+
+        VmaRestoreState *rstate = &vmar->rstate[dev_id];
+        BlockDriverState *bs = rstate->bs;
+        if (!bs) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "got wrong dev id %d", dev_id);
+            return -1;
+        }
+
+        if (vma_reader_get_bitmap(rstate, cluster_num)) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "found duplicated cluster %d for stream %s", cluster_num,
+                      vmar->devinfo[dev_id].devname);
+            return -1;
+        }
+
+        vma_reader_set_bitmap(rstate, cluster_num, 1);
+
+        int64_t max_sector = vmar->devinfo[dev_id].size/BDRV_SECTOR_SIZE;
+
+        /* try to write whole clusters to speedup restore */
+        if (mask == 0xffff) {
+            if ((start + VMA_CLUSTER_SIZE) > extend_size) {
+                error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                          "short vma extend - too many blocks");
+                return -1;
+            }
+            int64_t sector_num = (cluster_num * VMA_CLUSTER_SIZE) /
+                BDRV_SECTOR_SIZE;
+            int64_t end_sector = sector_num +
+                VMA_CLUSTER_SIZE/BDRV_SECTOR_SIZE;
+
+            if (end_sector > max_sector) {
+                end_sector = max_sector;
+            }
+
+            if (end_sector <= sector_num) {
+                error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                          "got wrong block address - write bejond end");
+                return -1;
+            }
+
+            int res = bdrv_write(bs, sector_num, buf + start,
+                                 end_sector - sector_num);
+            if (res < 0) {
+                error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                          "bdrv_write to %s failed (%d)",
+                          bdrv_get_device_name(bs), res);
+                return -1;
+            }
+            start += VMA_CLUSTER_SIZE;
+        } else {
+            int j;
+            int bit = 1;
+
+            for (j = 0; j < 16; j++) {
+                int64_t sector_num = (cluster_num*VMA_CLUSTER_SIZE +
+                                      j*VMA_BLOCK_SIZE)/BDRV_SECTOR_SIZE;
+
+                int64_t end_sector = sector_num +
+                    VMA_BLOCK_SIZE/BDRV_SECTOR_SIZE;
+                if (end_sector > max_sector) {
+                    end_sector = max_sector;
+                }
+
+                int res;
+                if (mask & bit) {
+                    if ((start + VMA_BLOCK_SIZE) > extend_size) {
+                        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                                  "short vma extend - too many blocks");
+                        return -1;
+                    }
+
+                    if (end_sector <= sector_num) {
+                        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                                  "got wrong block address - write bejond end");
+                        return -1;
+                    } else {
+                        res = bdrv_write(bs, sector_num, buf + start,
+                                         end_sector - sector_num);
+                        if (res < 0) {
+                            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                                      "bdrv_write to %s failed (%d)",
+                                      bdrv_get_device_name(bs), res);
+                            return -1;
+                        }
+                    }
+
+                    start += VMA_BLOCK_SIZE;
+
+                } else {
+
+                    if (rstate->write_zeroes & (end_sector > sector_num)) {
+                        /* Todo: use bdrv_co_write_zeroes (but that need to
+                         * be run inside coroutine?)
+                         */
+                        res = bdrv_write(bs, sector_num, zero_vma_block,
+                                         end_sector - sector_num);
+                        if (res < 0) {
+                            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                                      "bdrv_write zeros to %s failed (%d)",
+                                      bdrv_get_device_name(bs), res);
+                            return -1;
+                        }
+                    }
+                }
+
+                bit = bit << 1;
+            }
+        }
+    }
+
+    if (start != extend_size) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "vma extend error - missing blocks");
+        return -1;
+    }
+
+    return 0;
+}
+
+int vma_reader_restore(VmaReader *vmar, Error **errp)
+{
+    assert(vmar);
+    assert(vmar->head_data);
+
+    int ret = 0;
+    unsigned char buf[VMA_MAX_EXTEND_SIZE];
+    int buf_pos = 0;
+    unsigned char md5sum[16];
+    VmaHeader *h = (VmaHeader *)vmar->head_data;
+
+
+    while (1) {
+        int bytes = full_read(vmar->fd, buf + buf_pos, sizeof(buf) - buf_pos);
+        if (bytes < 0) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR, "read failed - %s",
+                      strerror(errno));
+            return -1;
+        }
+
+        buf_pos += bytes;
+
+        if (!buf_pos) {
+            break; /* EOF */
+        }
+
+        if (buf_pos < VMA_EXTEND_HEADER_SIZE) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "read short extend (%d bytes)", buf_pos);
+            return -1;
+        }
+
+        VmaExtendHeader *ehead = (VmaExtendHeader *)buf;
+
+        /* extract md5sum */
+        memcpy(md5sum, ehead->md5sum, sizeof(ehead->md5sum));
+        memset(ehead->md5sum, 0, sizeof(ehead->md5sum));
+
+        g_checksum_reset(vmar->md5csum);
+        g_checksum_update(vmar->md5csum, buf, VMA_EXTEND_HEADER_SIZE);
+        gsize csize = 16;
+        g_checksum_get_digest(vmar->md5csum, ehead->md5sum, &csize);
+
+        if (memcmp(md5sum, ehead->md5sum, 16) != 0) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "wrong vma extend header chechsum");
+            return -1;
+        }
+
+        if (memcmp(h->uuid, ehead->uuid, sizeof(ehead->uuid)) != 0) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR, "wrong vma extend uuid");
+            return -1;
+        }
+
+        if (ehead->magic != VMA_EXTEND_MAGIC || ehead->reserved1 != 0) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "wrong vma extend header magic");
+            return -1;
+        }
+
+        int block_count = GUINT16_FROM_BE(ehead->block_count);
+        int extend_size = VMA_EXTEND_HEADER_SIZE + block_count*VMA_BLOCK_SIZE;
+
+        if (buf_pos < extend_size) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "short vma extend (%d < %d)", buf_pos, extend_size);
+            return -1;
+        }
+
+        if (restore_extend(vmar, buf, extend_size, errp) < 0) {
+            return -1;
+        }
+
+        if (buf_pos > extend_size) {
+            memmove(buf, buf + extend_size, buf_pos - extend_size);
+            buf_pos = buf_pos - extend_size;
+        } else {
+            buf_pos = 0;
+        }
+    }
+
+    bdrv_drain_all();
+
+    int i;
+    for (i = 1; i < 256; i++) {
+        VmaRestoreState *rstate = &vmar->rstate[i];
+        if (!rstate->bs) {
+            continue;
+        }
+
+        if (bdrv_flush(rstate->bs) < 0) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "vma bdrv_flush %s failed", vmar->devinfo[i].devname);
+            return -1;
+        }
+
+        if (vmar->devinfo[i].size) {
+            assert(rstate->bitmap);
+
+            int64_t cluster_num, end;
+
+            end = (vmar->devinfo[i].size + VMA_CLUSTER_SIZE - 1) /
+                VMA_CLUSTER_SIZE;
+
+            for (cluster_num = 0; cluster_num < end; cluster_num++) {
+                if (!vma_reader_get_bitmap(rstate, cluster_num)) {
+                    error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                              "detected missing cluster %zd for stream %s",
+                              cluster_num, vmar->devinfo[i].devname);
+                    return -1;
+                }
+            }
+        }
+    }
+
+    return ret;
+}
+
diff --git a/vma-writer.c b/vma-writer.c
new file mode 100644
index 0000000..6aaa45d
--- /dev/null
+++ b/vma-writer.c
@@ -0,0 +1,824 @@ 
+/*
+ * VMA: Virtual Machine Archive
+ *
+ * Copyright (C) Proxmox Server Solutions
+ *
+ * Authors:
+ *  Dietmar Maurer (dietmar@proxmox.com)
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <glib.h>
+#include <uuid/uuid.h>
+
+#include "qemu-common.h"
+#include "qemu_socket.h"
+#include "qemu-coroutine.h"
+#include "qemu-aio.h"
+#include "qemu/ratelimit.h"
+#include "vma.h"
+#include "block.h"
+
+/* #define DEBUG_VMA */
+
+#ifdef DEBUG_VMA
+#define DPRINTF(fmt, ...) \
+    do { printf("vma: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) \
+    do { } while (0)
+#endif
+
+#define WRITE_BUFFERS 5
+
+typedef struct VmaAIOCB VmaAIOCB;
+struct VmaAIOCB {
+    VmaWriter *vmaw;
+    unsigned char buffer[VMA_MAX_EXTEND_SIZE];
+    size_t bytes;
+    Coroutine *co;
+};
+
+struct VmaWriter {
+    int fd;
+    FILE *cmd;
+    int status;
+    char errmsg[8192];
+    uuid_t uuid;
+    bool header_written;
+    bool closed;
+
+    /* we always write extends */
+    unsigned char outbuf[VMA_MAX_EXTEND_SIZE];
+    int outbuf_pos; /* in bytes */
+    int outbuf_count; /* in VMA_BLOCKS */
+    uint64_t outbuf_block_info[VMA_BLOCKS_PER_EXTEND];
+
+    VmaAIOCB aiocbs[WRITE_BUFFERS];
+    CoQueue wqueue;
+
+    GChecksum *md5csum;
+    CoMutex writer_lock;
+    CoMutex flush_lock;
+    Coroutine *co_writer;
+    RateLimit limit;
+    uint64_t delay_ns;
+
+    /* drive informations */
+    VmaStreamInfo stream_info[256];
+    guint stream_count;
+
+    /* header blob table */
+    char *header_blob_table;
+    uint32_t header_blob_table_size;
+    uint32_t header_blob_table_pos;
+
+    /* store for config blobs */
+    uint32_t config_names[VMA_MAX_CONFIGS]; /* offset into blob_buffer table */
+    uint32_t config_data[VMA_MAX_CONFIGS];  /* offset into blob_buffer table */
+    uint32_t config_count;
+
+    /* statistics */
+    uint64_t zero_block_count;
+    uint64_t total_bytes_written;
+};
+
+void vma_writer_set_error(VmaWriter *vmaw, const char *fmt, ...)
+{
+    va_list ap;
+
+    if (vmaw->status < 0) {
+        return;
+    }
+
+    vmaw->status = -1;
+
+    va_start(ap, fmt);
+    g_vsnprintf(vmaw->errmsg, sizeof(vmaw->errmsg), fmt, ap);
+    va_end(ap);
+
+    DPRINTF("vma_writer_set_error: %s\n", vmaw->errmsg);
+}
+
+static uint32_t allocate_header_blob(VmaWriter *vmaw, const char *data,
+                                     size_t len)
+{
+    if (len > 65535) {
+        return 0;
+    }
+
+    if (!vmaw->header_blob_table ||
+        (vmaw->header_blob_table_size <
+         (vmaw->header_blob_table_pos + len + 2))) {
+        int newsize = vmaw->header_blob_table_size + ((len + 2 + 511)/512)*512;
+
+        vmaw->header_blob_table = g_realloc(vmaw->header_blob_table, newsize);
+        memset(vmaw->header_blob_table + vmaw->header_blob_table_size,
+               0, newsize - vmaw->header_blob_table_size);
+        vmaw->header_blob_table_size = newsize;
+    }
+
+    uint32_t cpos = vmaw->header_blob_table_pos;
+    vmaw->header_blob_table[cpos] = len & 255;
+    vmaw->header_blob_table[cpos+1] = (len >> 8) & 255;
+    memcpy(vmaw->header_blob_table + cpos + 2, data, len);
+    vmaw->header_blob_table_pos += len + 2;
+    return cpos;
+}
+
+static uint32_t allocate_header_string(VmaWriter *vmaw, const char *str)
+{
+    assert(vmaw);
+
+    size_t len = strlen(str) + 1;
+
+    return allocate_header_blob(vmaw, str, len);
+}
+
+int vma_writer_add_config(VmaWriter *vmaw, const char *name, gpointer data,
+                          gsize len)
+{
+    assert(vmaw);
+    assert(!vmaw->header_written);
+    assert(vmaw->config_count < VMA_MAX_CONFIGS);
+    assert(name);
+    assert(data);
+    assert(len);
+
+    uint32_t name_ptr = allocate_header_string(vmaw, name);
+    if (!name_ptr) {
+        return -1;
+    }
+
+    uint32_t data_ptr = allocate_header_blob(vmaw, data, len);
+    if (!data_ptr) {
+        return -1;
+    }
+
+    vmaw->config_names[vmaw->config_count] = name_ptr;
+    vmaw->config_data[vmaw->config_count] = data_ptr;
+
+    vmaw->config_count++;
+
+    return 0;
+}
+
+int vma_writer_register_stream(VmaWriter *vmaw, const char *devname,
+                               size_t size)
+{
+    assert(vmaw);
+    assert(!vmaw->status);
+
+    if (vmaw->header_written) {
+        vma_writer_set_error(vmaw, "vma_writer_register_drive: header "
+                             "already written");
+        return -1;
+    }
+
+    guint n = vmaw->stream_count + 1;
+
+    /* we can have dev_ids form 1 to 255 (0 reserved)
+     * but 254 reserved for VM state
+     * 255(-1) reseverd for safety
+     */
+    if (n > 253) {
+        vma_writer_set_error(vmaw, "vma_writer_register_drive: "
+                             "too many drives");
+        return -1;
+    }
+
+    if (size <= 0) {
+        vma_writer_set_error(vmaw, "vma_writer_register_drive: "
+                             "got strange size %zd", size);
+        return -1;
+    }
+
+    DPRINTF("vma_writer_register_drive %s %zd %d", devname, size, n);
+
+    vmaw->stream_info[n].devname = g_strdup(devname);
+    vmaw->stream_info[n].size = size;
+
+    vmaw->stream_info[n].cluster_count = (size + VMA_CLUSTER_SIZE - 1) /
+        VMA_CLUSTER_SIZE;
+
+    vmaw->stream_count = n;
+
+    return n;
+}
+
+static void vma_co_continue_write(void *opaque)
+{
+    VmaWriter *vmaw = opaque;
+
+    qemu_aio_set_fd_handler(vmaw->fd, NULL, NULL, NULL, NULL);
+
+    DPRINTF("vma_co_continue_write\n");
+    qemu_coroutine_enter(vmaw->co_writer, NULL);
+}
+
+static ssize_t coroutine_fn
+vma_co_write(VmaWriter *vmaw, const void *buf, size_t bytes)
+{
+    size_t done = 0;
+    ssize_t ret;
+
+    /* atomic writes (we cannot interleave writes) */
+    qemu_co_mutex_lock(&vmaw->writer_lock);
+
+    DPRINTF("vma_co_write enter %zd\n", bytes);
+
+    while (done < bytes) {
+        ret = write(vmaw->fd, buf + done, bytes - done);
+        if (ret > 0) {
+            done += ret;
+            vmaw->total_bytes_written += ret;
+            DPRINTF("vma_co_write written %zd %zd\n", done, ret);
+        } else if (ret < 0) {
+            if (errno == EAGAIN || errno == EWOULDBLOCK) {
+                DPRINTF("vma_co_write yield %zd\n", done);
+
+                vmaw->co_writer = qemu_coroutine_self();
+                qemu_aio_set_fd_handler(vmaw->fd, NULL, vma_co_continue_write,
+                                        NULL, vmaw);
+
+                qemu_coroutine_yield();
+                DPRINTF("vma_co_write restart %zd\n", done);
+            } else {
+                vma_writer_set_error(vmaw, "vma_co_write write error - %s",
+                                     strerror(errno));
+                done = -1; /* always return failure for partial writes */
+                break;
+            }
+        } else if (ret == 0) {
+            /* should not happen - simply try again */
+        }
+    }
+
+    qemu_co_mutex_unlock(&vmaw->writer_lock);
+
+    DPRINTF("vma_co_write leave %zd\n", done);
+    return done;
+}
+
+static void coroutine_fn vma_co_writer_task(void *opaque)
+{
+    VmaAIOCB *cb = opaque;
+
+    DPRINTF("vma_co_writer_task start\n");
+
+    int64_t done = vma_co_write(cb->vmaw, cb->buffer, cb->bytes);
+    DPRINTF("vma_co_writer_task write done %zd\n", done);
+
+    if (done != cb->bytes) {
+        DPRINTF("vma_co_writer_task failed write %zd %zd", cb->bytes, done);
+        vma_writer_set_error(cb->vmaw, "vma_co_writer_task failed write %zd",
+                             done);
+    }
+
+    cb->bytes = 0;
+
+    qemu_co_queue_next(&cb->vmaw->wqueue);
+
+    DPRINTF("vma_co_writer_task end\n");
+}
+
+static void coroutine_fn vma_queue_flush(VmaWriter *vmaw)
+{
+    DPRINTF("vma_queue_flush enter\n");
+
+    assert(vmaw);
+
+    while (1) {
+        int i;
+        VmaAIOCB *cb = NULL;
+        for (i = 0; i < WRITE_BUFFERS; i++) {
+            if (vmaw->aiocbs[i].bytes) {
+                cb = &vmaw->aiocbs[i];
+                DPRINTF("FOUND USED AIO BUFFER %d %zd\n", i,
+                        vmaw->aiocbs[i].bytes);
+                break;
+            }
+        }
+        if (!cb) {
+            break;
+        }
+        qemu_co_queue_wait(&vmaw->wqueue);
+    }
+
+    DPRINTF("vma_queue_flush leave\n");
+}
+
+/**
+ * NOTE: pipe buffer size in only 4096 bytes on linux (see 'ulimit -a')
+ * So we need to create a coroutione to allow 'parallel' execution.
+ */
+static ssize_t coroutine_fn
+vma_queue_write(VmaWriter *vmaw, const void *buf, size_t bytes)
+{
+    DPRINTF("vma_queue_write enter %zd\n", bytes);
+
+    assert(vmaw);
+    assert(buf);
+    assert(bytes <= VMA_MAX_EXTEND_SIZE);
+
+    VmaAIOCB *cb = NULL;
+    while (!cb) {
+        int i;
+        for (i = 0; i < WRITE_BUFFERS; i++) {
+            if (!vmaw->aiocbs[i].bytes) {
+                cb = &vmaw->aiocbs[i];
+                break;
+            }
+        }
+        if (!cb) {
+            qemu_co_queue_wait(&vmaw->wqueue);
+        }
+    }
+
+    memcpy(cb->buffer, buf, bytes);
+    cb->bytes = bytes;
+    cb->vmaw = vmaw;
+
+    DPRINTF("vma_queue_write start %zd\n", bytes);
+    cb->co = qemu_coroutine_create(vma_co_writer_task);
+    qemu_coroutine_enter(cb->co, cb);
+
+    DPRINTF("vma_queue_write leave\n");
+
+    return bytes;
+}
+
+VmaWriter *vma_writer_create(const char *filename, int64_t speed, Error **errp)
+{
+    const char *p;
+
+    assert(sizeof(VmaHeader) == (4096 + 8192));
+    assert(sizeof(VmaExtendHeader) == 512);
+
+    VmaWriter *vmaw = g_new0(VmaWriter, 1);
+    vmaw->fd = -1;
+
+    vmaw->md5csum = g_checksum_new(G_CHECKSUM_MD5);
+    if (!vmaw->md5csum) {
+        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                  "can't allocate cmsum\n");
+        goto err;
+    }
+
+    if (strstart(filename, "exec:", &p)) {
+        vmaw->cmd = popen(p, "w");
+        if (vmaw->cmd == NULL) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "can't popen command '%s' - %s\n", p, strerror(errno));
+            goto err;
+        }
+        vmaw->fd = fileno(vmaw->cmd);
+        socket_set_nonblock(vmaw->fd);
+
+    } else {
+        vmaw->fd = open(filename, O_NONBLOCK|O_WRONLY|O_CREAT|O_EXCL, 0644);
+        if (vmaw->fd < 0) {
+            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
+                      "can't open file %s - %s\n", filename, strerror(errno));
+            goto err;
+        }
+    }
+
+    vmaw->outbuf_count = 0;
+    vmaw->outbuf_pos = VMA_EXTEND_HEADER_SIZE;
+
+    vmaw->header_blob_table_pos = 1; /* start at pos 1 */
+
+    qemu_co_mutex_init(&vmaw->writer_lock);
+    qemu_co_mutex_init(&vmaw->flush_lock);
+    qemu_co_queue_init(&vmaw->wqueue);
+
+    uuid_generate(vmaw->uuid);
+
+    if (speed <= 0) {
+        speed = 10*1024*1024*1024LLU; /* default 10GB/s */
+    }
+
+    ratelimit_set_speed(&vmaw->limit, speed, 100000000ULL /* 0.1 sec */);
+
+    return vmaw;
+
+err:
+    if (vmaw) {
+        if (vmaw->cmd) {
+            pclose(vmaw->cmd);
+        } else if (vmaw->fd >= 0) {
+            close(vmaw->fd);
+        }
+
+        if (vmaw->md5csum) {
+            g_checksum_free(vmaw->md5csum);
+        }
+
+        g_free(vmaw);
+    }
+
+    return NULL;
+}
+
+static int coroutine_fn vma_write_header(VmaWriter *vmaw)
+{
+    assert(vmaw);
+    int header_clusters = 8;
+    char buf[65536*header_clusters];
+    VmaHeader *head = (VmaHeader *)buf;
+
+    int i;
+
+    DPRINTF("VMA WRITE HEADER\n");
+
+    if (vmaw->status < 0) {
+        return vmaw->status;
+    }
+
+    memset(buf, 0, sizeof(buf));
+
+    head->magic = VMA_MAGIC;
+    head->version = GUINT32_TO_BE(1); /* v1 */
+    memcpy(head->uuid, vmaw->uuid, 16);
+
+    time_t ctime = time(NULL);
+    head->ctime = GUINT64_TO_BE(ctime);
+
+    if (!vmaw->stream_count) {
+        return -1;
+    }
+
+    for (i = 0; i < VMA_MAX_CONFIGS; i++) {
+        head->config_names[i] = GUINT32_TO_BE(vmaw->config_names[i]);
+        head->config_data[i] = GUINT32_TO_BE(vmaw->config_data[i]);
+    }
+
+    /* 32 bytes per device (12 used currently) = 8192 bytes max */
+    for (i = 1; i <= 254; i++) {
+        VmaStreamInfo *si = &vmaw->stream_info[i];
+        if (si->size) {
+            assert(si->devname);
+            uint32_t devname_ptr = allocate_header_string(vmaw, si->devname);
+            if (!devname_ptr) {
+                return -1;
+            }
+            head->dev_info[i].devname_ptr = GUINT32_TO_BE(devname_ptr);
+            head->dev_info[i].size = GUINT64_TO_BE(si->size);
+        }
+    }
+
+    uint32_t header_size = sizeof(VmaHeader) + vmaw->header_blob_table_size;
+    head->header_size = GUINT32_TO_BE(header_size);
+
+    if (header_size > sizeof(buf)) {
+        return -1; /* just to be sure */
+    }
+
+    uint32_t blob_buffer_offset = sizeof(VmaHeader);
+    memcpy(buf + blob_buffer_offset, vmaw->header_blob_table,
+           vmaw->header_blob_table_size);
+    head->blob_buffer_offset = GUINT32_TO_BE(blob_buffer_offset);
+    head->blob_buffer_size = GUINT32_TO_BE(vmaw->header_blob_table_pos);
+
+    g_checksum_reset(vmaw->md5csum);
+    g_checksum_update(vmaw->md5csum, (const guchar *)buf, header_size);
+    gsize csize = 16;
+    g_checksum_get_digest(vmaw->md5csum, (guint8 *)(head->md5sum), &csize);
+
+    return vma_queue_write(vmaw, buf, header_size);
+}
+
+static int coroutine_fn vma_writer_flush(VmaWriter *vmaw)
+{
+    assert(vmaw);
+
+    int ret;
+    int i;
+
+    if (vmaw->status < 0) {
+        return vmaw->status;
+    }
+
+    if (!vmaw->header_written) {
+        vmaw->header_written = true;
+        ret = vma_write_header(vmaw);
+        if (ret < 0) {
+            vma_writer_set_error(vmaw, "vma_writer_flush: write header failed");
+            return ret;
+        }
+    }
+
+    DPRINTF("VMA WRITE FLUSH %d %d %zd\n", vmaw->outbuf_count,
+           vmaw->outbuf_pos,
+           vmaw->zero_block_count);
+
+
+    VmaExtendHeader *ehead = (VmaExtendHeader *)vmaw->outbuf;
+
+    ehead->magic = VMA_EXTEND_MAGIC;
+    ehead->reserved1 = 0;
+
+    for (i = 0; i < VMA_BLOCKS_PER_EXTEND; i++) {
+        ehead->blockinfo[i] = GUINT64_TO_BE(vmaw->outbuf_block_info[i]);
+    }
+
+    guint16 block_count = (vmaw->outbuf_pos - VMA_EXTEND_HEADER_SIZE) /
+        VMA_BLOCK_SIZE;
+
+    ehead->block_count = GUINT16_TO_BE(block_count);
+
+    memcpy(ehead->uuid, vmaw->uuid, sizeof(ehead->uuid));
+    memset(ehead->md5sum, 0, sizeof(ehead->md5sum));
+
+    g_checksum_reset(vmaw->md5csum);
+    g_checksum_update(vmaw->md5csum, vmaw->outbuf, VMA_EXTEND_HEADER_SIZE);
+    gsize csize = 16;
+    g_checksum_get_digest(vmaw->md5csum, ehead->md5sum, &csize);
+
+    int bytes = vmaw->outbuf_pos;
+    ret = vma_queue_write(vmaw, vmaw->outbuf, bytes);
+    if (ret != bytes) {
+        vma_writer_set_error(vmaw, "vma_writer_flush: failed write");
+    }
+
+    vmaw->outbuf_count = 0;
+    vmaw->outbuf_pos = VMA_EXTEND_HEADER_SIZE;
+
+    for (i = 0; i < VMA_BLOCKS_PER_EXTEND; i++) {
+        vmaw->outbuf_block_info[i] = 0;
+    }
+
+    return vmaw->status;
+}
+
+static int vma_count_open_streams(VmaWriter *vmaw)
+{
+    g_assert(vmaw != NULL);
+
+    int i;
+    int open_drives = 0;
+    for (i = 0; i <= 255; i++) {
+        if (vmaw->stream_info[i].size && !vmaw->stream_info[i].finished) {
+            open_drives++;
+        }
+    }
+
+    return open_drives;
+}
+
+/**
+ * all jobs should call this when there is no more data
+ * Returns: number of remaining stream (0 ==> finished)
+ */
+int coroutine_fn
+vma_writer_close_stream(VmaWriter *vmaw, uint8_t dev_id)
+{
+    g_assert(vmaw != NULL);
+
+    DPRINTF("vma_writer_set_status %d\n", dev_id);
+    if (!vmaw->stream_info[dev_id].size) {
+        vma_writer_set_error(vmaw, "vma_writer_close_stream: "
+                             "no such stream %d", dev_id);
+        return -1;
+    }
+    if (vmaw->stream_info[dev_id].finished) {
+        vma_writer_set_error(vmaw, "vma_writer_close_stream: "
+                             "stream already closed %d", dev_id);
+        return -1;
+    }
+
+    vmaw->stream_info[dev_id].finished = true;
+
+    int open_drives = vma_count_open_streams(vmaw);
+
+    if (open_drives <= 0) {
+        DPRINTF("vma_writer_set_status all drives completed\n");
+        qemu_co_mutex_lock(&vmaw->flush_lock);
+        int ret = vma_writer_flush(vmaw);
+        qemu_co_mutex_unlock(&vmaw->flush_lock);
+        if (ret < 0) {
+            vma_writer_set_error(vmaw, "vma_writer_close_stream: flush failed");
+        }
+    }
+
+    return open_drives;
+}
+
+int vma_writer_get_status(VmaWriter *vmaw, VmaStatus *status)
+{
+    int i;
+
+    g_assert(vmaw != NULL);
+
+    if (status) {
+        status->status = vmaw->status;
+        g_strlcpy(status->errmsg, vmaw->errmsg, sizeof(status->errmsg));
+        for (i = 0; i <= 255; i++) {
+            status->stream_info[i] = vmaw->stream_info[i];
+        }
+
+        uuid_unparse_lower(vmaw->uuid, status->uuid_str);
+    }
+
+    status->closed = vmaw->closed;
+
+    return vmaw->status;
+}
+
+static int vma_writer_get_buffer(VmaWriter *vmaw)
+{
+
+    /* wait until buffer is available */
+    while (vmaw->outbuf_count >= (VMA_BLOCKS_PER_EXTEND - 1)) {
+        int res = 0;
+
+        qemu_co_mutex_lock(&vmaw->flush_lock);
+        res = vma_writer_flush(vmaw);
+        qemu_co_mutex_unlock(&vmaw->flush_lock);
+
+        if (res < 0) {
+            vma_writer_set_error(vmaw, "vma_writer_get_buffer: flush failed");
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+
+int64_t coroutine_fn
+vma_writer_write(VmaWriter *vmaw, uint8_t dev_id, int64_t cluster_num,
+                 unsigned char *buf)
+{
+    g_assert(vmaw != NULL);
+
+    if (vmaw->status < 0) {
+        return vmaw->status;
+    }
+
+    if (!dev_id || !vmaw->stream_info[dev_id].size) {
+        vma_writer_set_error(vmaw, "vma_writer_write: "
+                             "no such stream %d", dev_id);
+        return -1;
+    }
+
+    if (vmaw->stream_info[dev_id].finished) {
+        vma_writer_set_error(vmaw, "vma_writer_write: "
+                             "stream already closed %d", dev_id);
+        return -1;
+    }
+
+
+    if (cluster_num >= (((uint64_t)1)<<32)) {
+        vma_writer_set_error(vmaw, "vma_writer_write: "
+                             "cluster number out of range");
+        return -1;
+    }
+
+    if (cluster_num >= vmaw->stream_info[dev_id].cluster_count) {
+        vma_writer_set_error(vmaw, "vma_writer_write: cluster number too big");
+        return -1;
+    }
+
+    /* wait until buffer is available */
+    if (vma_writer_get_buffer(vmaw) < 0) {
+        vma_writer_set_error(vmaw, "vma_writer_write: "
+                             "vma_writer_get_buffer failed");
+        return -1;
+    }
+
+    DPRINTF("VMA WRITE %zd\n", cluster_num);
+
+    int i;
+    int bit = 1;
+    uint16_t mask = 0;
+    for (i = 0; i < 16; i++) {
+        unsigned char *vmablock = buf + (i*VMA_BLOCK_SIZE);
+        if (buffer_is_zero(vmablock, VMA_BLOCK_SIZE)) {
+            DPRINTF("VMA WRITE %zd ZERO BLOCK %d\n", cluster_num, i);
+            vmaw->zero_block_count++;
+            vmaw->stream_info[dev_id].zero_bytes += VMA_BLOCK_SIZE;
+        } else {
+            mask |= bit;
+            memcpy(vmaw->outbuf + vmaw->outbuf_pos, vmablock, VMA_BLOCK_SIZE);
+            vmaw->outbuf_pos += VMA_BLOCK_SIZE;
+
+            vmaw->delay_ns = ratelimit_calculate_delay(&vmaw->limit,
+                                                       VMA_BLOCK_SIZE);
+            if (vmaw->delay_ns) {
+                co_sleep_ns(rt_clock, vmaw->delay_ns);
+            }
+        }
+
+        bit = bit << 1;
+    }
+
+    uint64_t block_info = ((uint64_t)mask) << (32+16);
+    block_info |= ((uint64_t)dev_id) << 32;
+    block_info |= (cluster_num & 0xffffffff);
+    vmaw->outbuf_block_info[vmaw->outbuf_count] =  block_info;
+
+    DPRINTF("VMA WRITE MASK %zd %zx\n", cluster_num, block_info);
+
+    vmaw->outbuf_count++;
+
+    vmaw->stream_info[dev_id].transferred += VMA_CLUSTER_SIZE;
+
+    /** NOTE: We allways write whole clusters, but we correctly set
+     * transferred bytes. So transferred == size when when everything
+     * went OK.
+     */
+    uint64_t last = (cluster_num + 1) * VMA_CLUSTER_SIZE;
+    if (last > vmaw->stream_info[dev_id].size) {
+        uint64_t diff = last - vmaw->stream_info[dev_id].size;
+        if (diff >= VMA_CLUSTER_SIZE) {
+            vma_writer_set_error(vmaw, "vma_writer_write: "
+                                 "read after last cluster");
+            return -1;
+        }
+        vmaw->stream_info[dev_id].transferred -= diff;
+    }
+
+    return vmaw->total_bytes_written;
+}
+
+int vma_writer_close(VmaWriter *vmaw)
+{
+    g_assert(vmaw != NULL);
+
+    int i;
+
+    vma_queue_flush(vmaw);
+
+    /* this should not happen - just to be sure */
+    while (!qemu_co_queue_empty(&vmaw->wqueue)) {
+        DPRINTF("vma_writer_close wait\n");
+        co_sleep_ns(rt_clock, 1000000);
+    }
+
+    if (vmaw->cmd) {
+        if (pclose(vmaw->cmd) < 0) {
+            vma_writer_set_error(vmaw, "vma_writer_close: "
+                                 "pclose failed - %s", strerror(errno));
+        }
+    } else {
+        if (close(vmaw->fd) < 0) {
+            vma_writer_set_error(vmaw, "vma_writer_close: "
+                                 "close failed - %s", strerror(errno));
+        }
+    }
+
+    for (i = 0; i <= 255; i++) {
+        VmaStreamInfo *si = &vmaw->stream_info[i];
+        if (si->size) {
+            if (!si->finished) {
+                vma_writer_set_error(vmaw, "vma_writer_close: "
+                                     "detected open stream '%s'", si->devname);
+            } else if (si->transferred != si->size) {
+                vma_writer_set_error(vmaw, "vma_writer_close: "
+                                     "incomplete stream '%s' (%zd != %zd)",
+                                     si->devname, si->transferred, si->size);
+            }
+        }
+    }
+
+    for (i = 0; i <= 255; i++) {
+        vmaw->stream_info[i].finished = 1; /* mark as closed */
+    }
+
+    vmaw->closed = 1;
+
+    return vmaw->status;
+}
+
+void vma_writer_destroy(VmaWriter *vmaw)
+{
+    assert(vmaw);
+
+    int i;
+
+    for (i = 0; i <= 255; i++) {
+        if (vmaw->stream_info[i].devname) {
+            g_free(vmaw->stream_info[i].devname);
+        }
+    }
+
+    if (vmaw->md5csum) {
+        g_checksum_free(vmaw->md5csum);
+    }
+
+    g_free(vmaw);
+}
+
diff --git a/vma.c b/vma.c
new file mode 100644
index 0000000..f8336bf
--- /dev/null
+++ b/vma.c
@@ -0,0 +1,526 @@ 
+/*
+ * VMA: Virtual Machine Archive
+ *
+ * Copyright (C) Proxmox Server Solutions
+ *
+ * Authors:
+ *  Dietmar Maurer (dietmar@proxmox.com)
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <glib.h>
+
+#include "qemu-common.h"
+#include "qemu-option.h"
+#include "qemu-error.h"
+#include "osdep.h"
+#include "sysemu.h"
+#include "block_int.h"
+#include <stdio.h>
+#include "vma.h"
+
+static void help(void)
+{
+    const char *help_msg =
+        "usage: vma command [command options]\n"
+        "\n"
+        "vma list <filename>\n"
+        "vma create <filename> [-c config] <archive> pathname ...\n"
+        "vma extract <filename> [-r] <targetdir>\n"
+        ;
+
+    printf("%s", help_msg);
+    exit(1);
+}
+
+static const char *extract_devname(const char *path, char **devname, int index)
+{
+    assert(path);
+
+    const char *sep = strchr(path, '=');
+
+    if (sep) {
+        *devname = g_strndup(path, sep - path);
+        path = sep + 1;
+    } else {
+        if (index >= 0) {
+            *devname = g_strdup_printf("disk%d", index);
+        } else {
+            *devname = NULL;
+        }
+    }
+
+    return path;
+}
+
+static void print_content(VmaReader *vmar)
+{
+    assert(vmar);
+
+    VmaHeader *head = vma_reader_get_header(vmar);
+
+    printf("CTIME: %s", ctime(&head->ctime));
+
+    GList *l = vma_reader_get_config_data(vmar);
+    while (l && l->data) {
+        VmaConfigData *cdata = (VmaConfigData *)l->data;
+        l = g_list_next(l);
+        printf("CFG: size: %d name: %s\n", cdata->len, cdata->name);
+    }
+
+    int i;
+    VmaDeviceInfo *di;
+    for (i = 1; i < 255; i++) {
+        di = vma_reader_get_device_info(vmar, i);
+        if (di) {
+            printf("DEV: dev_id=%d size: %zd devname: %s\n",
+                   i, di->size, di->devname);
+        }
+    }
+}
+
+static int list_content(int argc, char **argv)
+{
+    int c, ret = 0;
+    const char *filename;
+
+    for (;;) {
+        c = getopt(argc, argv, "h");
+        if (c == -1) {
+            break;
+        }
+        switch (c) {
+        case '?':
+        case 'h':
+            help();
+            break;
+        default:
+            g_assert_not_reached();
+        }
+    }
+
+    /* Get the filename */
+    if ((optind + 1) != argc) {
+        help();
+    }
+    filename = argv[optind++];
+
+    Error *errp = NULL;
+    VmaReader *vmar = vma_reader_create(filename, &errp);
+
+    if (!vmar) {
+        g_error("%s", error_get_pretty(errp));
+    }
+
+    print_content(vmar);
+
+    vma_reader_destroy(vmar);
+
+    return ret;
+}
+
+typedef struct RestoreMap {
+    char *devname;
+    char *path;
+    bool write_zero;
+} RestoreMap;
+
+static int extract_content(int argc, char **argv)
+{
+    int c, ret = 0;
+    const char *filename;
+    const char *dirname;
+    int readmap = 0;
+
+    for (;;) {
+        c = getopt(argc, argv, "hr");
+        if (c == -1) {
+            break;
+        }
+        switch (c) {
+        case '?':
+        case 'h':
+            help();
+            break;
+        case 'r':
+            readmap = 1;
+            break;
+        default:
+            help();
+        }
+    }
+
+    /* Get the filename */
+    if ((optind + 2) != argc) {
+        help();
+    }
+    filename = argv[optind++];
+    dirname = argv[optind++];
+
+    Error *errp = NULL;
+    VmaReader *vmar = vma_reader_create(filename, &errp);
+
+    if (!vmar) {
+        g_error("%s", error_get_pretty(errp));
+    }
+
+    if (mkdir(dirname, 0777) < 0) {
+        g_error("unable to create target directory %s - %s",
+                dirname, strerror(errno));
+    }
+
+    GList *l = vma_reader_get_config_data(vmar);
+    while (l && l->data) {
+        VmaConfigData *cdata = (VmaConfigData *)l->data;
+        l = g_list_next(l);
+        char *cfgfn = g_strdup_printf("%s/%s", dirname, cdata->name);
+        GError *err = NULL;
+        if (!g_file_set_contents(cfgfn, (gchar *)cdata->data, cdata->len,
+                                 &err)) {
+            g_error("Unable to write file: %s", err->message);
+        }
+    }
+
+    GHashTable *devmap = g_hash_table_new(g_str_hash, g_str_equal);
+
+    if (readmap) {
+        print_content(vmar);
+
+        while (1) {
+            char inbuf[8192];
+            char *line = fgets(inbuf, sizeof(inbuf), stdin);
+            if (!line || line[0] == '\0' || !strcmp(line, "done\n")) {
+                break;
+            }
+            int len = strlen(line);
+            if (line[len - 1] == '\n') {
+                line[len - 1] = '\0';
+                if (len == 1) {
+                    break;
+                }
+            }
+
+            const char *path;
+            bool write_zero;
+            if (line[0] == '0' && line[1] == ':') {
+                path = inbuf + 2;
+                write_zero = false;
+            } else if (line[0] == '1' && line[1] == ':') {
+                path = inbuf + 2;
+                write_zero = true;
+           } else {
+                g_error("read map failed - parse error ('%s')", inbuf);
+            }
+
+            char *devname = NULL;
+            path = extract_devname(path, &devname, -1);
+            if (!devname) {
+                g_error("read map failed - no dev name specified ('%s')",
+                        inbuf);
+            }
+
+            printf("TEST %s %s\n", path, devname);
+
+            RestoreMap *map = g_new0(RestoreMap, 1);
+            map->devname = g_strdup(devname);
+            map->path = g_strdup(path);
+            map->write_zero = write_zero;
+
+            g_hash_table_insert(devmap, map->devname, map);
+
+        };
+    }
+
+    int i;
+    for (i = 1; i < 255; i++) {
+        VmaDeviceInfo *di = vma_reader_get_device_info(vmar, i);
+        if (di) {
+            char *devfn = NULL;
+            int flags = BDRV_O_RDWR|BDRV_O_CACHE_WB;
+            bool write_zero = true;
+
+            if (readmap) {
+                RestoreMap *map;
+                map = (RestoreMap *)g_hash_table_lookup(devmap, di->devname);
+                if (map == NULL) {
+                    g_error("no device name mapping for %s", di->devname);
+                }
+                devfn = map->path;
+                write_zero = map->write_zero;
+            } else {
+                devfn = g_strdup_printf("%s/tmp-disk-%s.raw",
+                                        dirname, di->devname);
+                printf("DEVINFO %s %zd\n", devfn, di->size);
+
+                if (bdrv_img_create(devfn, "raw", NULL, NULL, NULL,
+                                    di->size, flags)) {
+                    g_error("can't create file %s", devfn);
+                }
+                /* Note: if we created an empty file above, there is no need
+                 * to write zeroes (so we generate a sparse file)
+                 */
+                write_zero = false;
+            }
+
+            BlockDriverState *bs = NULL;
+            if (bdrv_file_open(&bs, devfn, flags)) {
+                g_error("can't open file %s", devfn);
+            }
+            if (vma_reader_register_bs(vmar, i, bs, write_zero, &errp) < 0) {
+                g_error("%s", error_get_pretty(errp));
+            }
+
+            if (!readmap) {
+                g_free(devfn);
+            }
+        }
+    }
+
+    if (vma_reader_restore(vmar, &errp) < 0) {
+        g_error("restore failed - %s", error_get_pretty(errp));
+    }
+
+    if (!readmap) {
+        for (i = 1; i < 255; i++) {
+            VmaDeviceInfo *di = vma_reader_get_device_info(vmar, i);
+            if (di) {
+                char *tmpfn = g_strdup_printf("%s/tmp-disk-%s.raw",
+                                              dirname, di->devname);
+                char *fn = g_strdup_printf("%s/disk-%s.raw",
+                                           dirname, di->devname);
+                if (rename(tmpfn, fn) != 0) {
+                    g_error("rename %s to %s failed - %s",
+                            tmpfn, fn, strerror(errno));
+                }
+            }
+        }
+    }
+
+    vma_reader_destroy(vmar);
+
+    bdrv_close_all();
+
+    return ret;
+}
+
+typedef struct BackupCB {
+    VmaWriter *vmaw;
+    uint8_t dev_id;
+} BackupCB;
+
+static int backup_dump_cb(void *opaque, BlockDriverState *bs,
+                          int64_t cluster_num, unsigned char *buf)
+{
+    BackupCB *bcb = opaque;
+
+    if (vma_writer_write(bcb->vmaw, bcb->dev_id, cluster_num, buf) < 0) {
+        g_warning("backup_dump_cb vma_writer_write failed");
+        return -1;
+    }
+
+    return 0;
+}
+
+static void backup_complete_cb(void *opaque, int ret)
+{
+    BackupCB *bcb = opaque;
+
+    if (ret < 0) {
+        vma_writer_set_error(bcb->vmaw, "backup_complete_cb %d", ret);
+    }
+
+    if (vma_writer_close_stream(bcb->vmaw, bcb->dev_id) <= 0) {
+        if (vma_writer_close(bcb->vmaw) != 0) {
+            g_warning("vma_writer_close failed");
+        }
+    }
+}
+
+static int create_archive(int argc, char **argv)
+{
+    int i, c, res;
+    int verbose = 0;
+    const char *archivename;
+    GList *config_files = NULL;
+
+    for (;;) {
+        c = getopt(argc, argv, "hvc:");
+        if (c == -1) {
+            break;
+        }
+        switch (c) {
+        case '?':
+        case 'h':
+            help();
+            break;
+        case 'c':
+            config_files = g_list_append(config_files, optarg);
+            break;
+        case 'v':
+            verbose = 1;
+            break;
+        default:
+            g_assert_not_reached();
+        }
+    }
+
+
+    /* make sure we have archive name and at least one path */
+    if ((optind + 2) > argc) {
+        help();
+    }
+
+    archivename = argv[optind++];
+
+    Error *local_err = NULL;
+    VmaWriter *vmaw = vma_writer_create(archivename, 0, &local_err);
+
+    if (vmaw == NULL) {
+        g_error("%s", error_get_pretty(local_err));
+    }
+
+    GList *l = config_files;
+    while (l && l->data) {
+        char *name = l->data;
+        char *cdata = NULL;
+        gsize clen = 0;
+        GError *err = NULL;
+        if (!g_file_get_contents(name, &cdata, &clen, &err)) {
+            unlink(archivename);
+            g_error("Unable to read file: %s", err->message);
+        }
+
+        if (vma_writer_add_config(vmaw, name, cdata, clen) != 0) {
+            unlink(archivename);
+            g_error("Unable to append config data %s (len = %zd)",
+                    name, clen);
+        }
+        l = g_list_next(l);
+    }
+
+    int ind = 0;
+    while (optind < argc) {
+        const char *path = argv[optind++];
+        char *devname = NULL;
+        path = extract_devname(path, &devname, ind++);
+
+        BlockDriver *drv = NULL;
+        BlockDriverState *bs = bdrv_new(devname);
+
+        res = bdrv_open(bs, path, BDRV_O_CACHE_WB , drv);
+        if (res < 0) {
+            unlink(archivename);
+            g_error("bdrv_open '%s' failed", path);
+        }
+        int64_t size = bdrv_getlength(bs);
+        int dev_id = vma_writer_register_stream(vmaw, devname, size);
+        if (dev_id <= 0) {
+            unlink(archivename);
+            g_error("vma_writer_register_stream '%s' failed", devname);
+        }
+
+        BackupCB *bcb = g_new0(BackupCB, 1);
+        bcb->vmaw = vmaw;
+        bcb->dev_id = dev_id;
+
+        bdrv_backup_init(bs, backup_dump_cb, backup_complete_cb, bcb);
+    }
+
+    VmaStatus vmastat;
+    int percent = 0;
+    int last_percent = -1;
+
+    while (1) {
+        main_loop_wait(false);
+        vma_writer_get_status(vmaw, &vmastat);
+
+        if (verbose) {
+
+            uint64_t total = 0;
+            uint64_t transferred = 0;
+            uint64_t zero_bytes = 0;
+
+            int i;
+            for (i = 0; i < 256; i++) {
+                if (vmastat.stream_info[i].size) {
+                    total += vmastat.stream_info[i].size;
+                    transferred += vmastat.stream_info[i].transferred;
+                    zero_bytes += vmastat.stream_info[i].zero_bytes;
+                }
+            }
+            percent = (transferred*100)/total;
+            if (percent != last_percent) {
+                printf("progress %d%% %zd/%zd %zd\n", percent,
+                       transferred, total, zero_bytes);
+
+                last_percent = percent;
+            }
+        }
+
+        if (vmastat.closed) {
+            break;
+        }
+    }
+
+    bdrv_drain_all();
+
+    vma_writer_get_status(vmaw, &vmastat);
+
+    if (verbose) {
+        for (i = 0; i < 256; i++) {
+            VmaStreamInfo *si = &vmastat.stream_info[i];
+            if (si->size) {
+                printf("image %s: size=%zd zeros=%zd saved=%zd\n", si->devname,
+                       si->size, si->zero_bytes, si->size - si->zero_bytes);
+            }
+        }
+    }
+
+    if (vmastat.status < 0) {
+        unlink(archivename);
+        g_error("creating vma archive failed");
+    }
+
+    return 0;
+}
+
+int main(int argc, char **argv)
+{
+    const char *cmdname;
+
+    error_set_progname(argv[0]);
+
+    qemu_init_main_loop();
+
+    bdrv_init();
+
+    if (argc < 2) {
+        help();
+    }
+
+    cmdname = argv[1];
+    argc--; argv++;
+
+
+    if (!strcmp(cmdname, "list")) {
+        return list_content(argc, argv);
+    } else if (!strcmp(cmdname, "create")) {
+        return create_archive(argc, argv);
+    } else if (!strcmp(cmdname, "extract")) {
+        return extract_content(argc, argv);
+    }
+
+    help();
+    return 0;
+}
diff --git a/vma.h b/vma.h
new file mode 100644
index 0000000..7c40d1b
--- /dev/null
+++ b/vma.h
@@ -0,0 +1,139 @@ 
+/*
+ * VMA: Virtual Machine Archive
+ *
+ * Copyright (C) Proxmox Server Solutions
+ *
+ * Authors:
+ *  Dietmar Maurer (dietmar@proxmox.com)
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef BACKUP_VMA_H
+#define BACKUP_VMA_H
+
+#include "error.h"
+
+#define VMA_BLOCK_BITS 12
+#define VMA_BLOCK_SIZE (1<<VMA_BLOCK_BITS)
+#define VMA_CLUSTER_BITS (VMA_BLOCK_BITS+4)
+#define VMA_CLUSTER_SIZE (1<<VMA_CLUSTER_BITS)
+
+#if VMA_CLUSTER_SIZE != 65536
+#error unexpected cluster size
+#endif
+
+#define VMA_EXTEND_HEADER_SIZE 512
+#define VMA_BLOCKS_PER_EXTEND 59
+#define VMA_MAX_CONFIGS 256
+
+#define VMA_MAX_EXTEND_SIZE \
+    (VMA_EXTEND_HEADER_SIZE+VMA_CLUSTER_SIZE*VMA_BLOCKS_PER_EXTEND)
+#if VMA_MAX_EXTEND_SIZE != 3867136
+#error unexpected VMA_EXTEND_SIZE
+#endif
+
+/* File Format Definitions */
+
+#define VMA_MAGIC (GUINT32_TO_BE(('V'<<24)|('M'<<16)|('A'<<8)|0x00))
+#define VMA_EXTEND_MAGIC (GUINT32_TO_BE(('V'<<24)|('M'<<16)|('A'<<8)|'E'))
+
+typedef struct VmaDeviceInfoHeader {
+    uint32_t devname_ptr; /* offset into blob_buffer table */
+    uint32_t reserved0;
+    uint64_t size; /* device size in bytes */
+    uint64_t reserved1;
+    uint64_t reserved2;
+} VmaDeviceInfoHeader;
+
+typedef struct VmaHeader {
+    uint32_t magic;
+    uint32_t version;
+    unsigned char uuid[16];
+    int64_t ctime;
+    unsigned char md5sum[16];
+
+    uint32_t blob_buffer_offset;
+    uint32_t blob_buffer_size;
+    uint32_t header_size;
+
+    unsigned char reserved[1984];
+
+    uint32_t config_names[VMA_MAX_CONFIGS]; /* offset into blob_buffer table */
+    uint32_t config_data[VMA_MAX_CONFIGS];  /* offset into blob_buffer table */
+
+    VmaDeviceInfoHeader dev_info[256];
+} VmaHeader;
+
+typedef struct VmaExtendHeader {
+    uint32_t magic;
+    uint16_t reserved1;
+    uint16_t block_count;
+    unsigned char uuid[16];
+    unsigned char md5sum[16];
+    uint64_t blockinfo[VMA_BLOCKS_PER_EXTEND];
+} VmaExtendHeader;
+
+/* functions/definitions to read/write vma files */
+
+typedef struct VmaReader VmaReader;
+
+typedef struct VmaWriter VmaWriter;
+
+typedef struct VmaConfigData {
+    const unsigned char *name;
+    const unsigned char *data;
+    uint32_t len;
+} VmaConfigData;
+
+typedef struct VmaStreamInfo {
+    uint64_t size;
+    uint64_t cluster_count;
+    uint64_t transferred;
+    uint64_t zero_bytes;
+    int finished;
+    char *devname;
+} VmaStreamInfo;
+
+typedef struct VmaStatus {
+    int status;
+    bool closed;
+    char errmsg[8192];
+    char uuid_str[37];
+    VmaStreamInfo stream_info[256];
+} VmaStatus;
+
+typedef struct VmaDeviceInfo {
+    uint64_t size; /* device size in bytes */
+    const unsigned char *devname;
+} VmaDeviceInfo;
+
+VmaWriter *vma_writer_create(const char *filename, int64_t speed, Error **errp);
+int vma_writer_close(VmaWriter *vmaw);
+void vma_writer_destroy(VmaWriter *vmaw);
+int vma_writer_add_config(VmaWriter *vmaw, const char *name, gpointer data,
+                          size_t len);
+int vma_writer_register_stream(VmaWriter *vmaw, const char *devname,
+                               size_t size);
+
+int64_t coroutine_fn vma_writer_write(VmaWriter *vmaw, uint8_t dev_id,
+                                      int64_t cluster_num, unsigned char *buf);
+int coroutine_fn vma_writer_close_stream(VmaWriter *vmaw, uint8_t dev_id);
+
+int vma_writer_get_status(VmaWriter *vmaw, VmaStatus *status);
+void vma_writer_set_error(VmaWriter *vmaw, const char *fmt, ...);
+
+
+VmaReader *vma_reader_create(const char *filename, Error **errp);
+void vma_reader_destroy(VmaReader *vmar);
+VmaHeader *vma_reader_get_header(VmaReader *vmar);
+GList *vma_reader_get_config_data(VmaReader *vmar);
+VmaDeviceInfo *vma_reader_get_device_info(VmaReader *vmar, guint8 dev_id);
+int vma_reader_register_bs(VmaReader *vmar, guint8 dev_id,
+                           BlockDriverState *bs, bool write_zeroes,
+                           Error **errp);
+int vma_reader_restore(VmaReader *vmar, Error **errp);
+
+#endif /* BACKUP_VMA_H */