[Qemu-devel] [PATCH 0/2] block: drive_add/del without BlockBackend

[Qemu-devel] [PATCH 0/2] block: drive_add/del without BlockBackend

[Kevin Wolf]

See patch 1 for the detailed description why this is needed. The short
version is that libvirt needs to enable detect-zeroes on a mirror
target.

Peter, can you please check if this provides what you need? I checked
whether I could do the mirroring operation manually; and if I did it
right, it looks good to me. (Shortened) protocol of my test:

$ ./qemu-img create -f qcow2 /tmp/test.qcow2 64M
Formatting '/tmp/test.qcow2', fmt=qcow2 size=67108864 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16

$ ./qemu-io -c 'write -P 0 0 64M' /tmp/test.qcow2 
wrote 67108864/67108864 bytes at offset 0
64 MiB, 1 ops; 0.3141 sec (203.694 MiB/sec and 3.1827 ops/sec)

$ ls -lh /tmp/test.qcow2 
-rw-r--r--. 1 kwolf kwolf 65M 23. Feb 17:57 /tmp/test.qcow2

$ ./qemu-img create -f qcow2 /tmp/copy.qcow2 64M
Formatting '/tmp/copy.qcow2', fmt=qcow2 size=67108864 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16

$ x86_64-softmmu/qemu-system-x86_64 -qmp stdio -hda /tmp/test.qcow2
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 5, "major": 2}, "package": ""}, "capabilities": []}}
{"execute":"qmp_capabilities"}
{"return": {}}
{"execute":"human-monitor-command","arguments":{"command-line":"drive_add -n 0 file.filename=/tmp/copy.qcow2,node-name=copy,detect-zeroes=on"}}
{"return": ""}
{"execute":"blockdev-mirror","arguments":{"device":"ide0-hd0","target":"copy","sync":"full"}}
{"return": {}}
{"timestamp": {"seconds": 1456247099, "microseconds": 895774}, "event": "BLOCK_JOB_READY", "data": {"device": "ide0-hd0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "mirror"}}
{"execute":"block-job-complete","arguments":{"device":"ide0-hd0"}}
{"return": {}}
{"timestamp": {"seconds": 1456247127, "microseconds": 552227}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "ide0-hd0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "mirror"}}

$ ls -lh /tmp/copy.qcow2 
-rw-r--r--. 1 kwolf kwolf 320K 23. Feb 18:04 /tmp/copy.qcow2

Kevin Wolf (2):
  hmp: 'drive_add -n' for creating a node without BB
  hmp: Extend drive_del to delete nodes without BB

 blockdev.c                | 39 +++++++++++++++++++++++++++++++++++++++
 device-hotplug.c          |  7 +++++++
 hmp-commands.hx           |  4 ++--
 include/block/block_int.h |  2 ++
 4 files changed, 50 insertions(+), 2 deletions(-)

-- 
1.8.3.1

[Qemu-devel] [PATCH 1/2] hmp: 'drive_add -n' for creating a node without BB

[Kevin Wolf]

This patch adds an option to the drive_add HMP command to create only a
BlockDriverState without a BlockBackend on top.

The motivation for this is that libvirt needs to specify options to a
migration target (specifically, detect-zeroes). drive-mirror doesn't
allow specifying options, and the proper way to do this is to create the
target BDS separately with blockdev-add (where you can specify options)
and then use blockdev-mirror to that BDS.

However, libvirt can't use blockdev-add as long as it is still
experimental, and we're expecting that it will still take some time, so
we need to resort to drive_add.

The problem with drive_add is that so far it always created a BB, and
BDSes with a BB can't be used as a mirroring target as long as we don't
support multiple BBs per BDS - and while we're working towards that
goal, it's another thing that will still take some time.

So to achieve the goal, the simplest solution to provide the
functionality now without adding one-off options to the mirror QMP
commands is to extend drive_add to create nodes without BBs.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 blockdev.c                | 30 ++++++++++++++++++++++++++++++
 device-hotplug.c          |  7 +++++++
 hmp-commands.hx           |  4 ++--
 include/block/block_int.h |  2 ++
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index d4bc435..3f46bc1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3867,6 +3867,36 @@ out:
     aio_context_release(aio_context);
 }
 
+void hmp_drive_add_node(Monitor *mon, const char *optstr)
+{
+    QemuOpts *opts;
+    QDict *qdict;
+    Error *local_err = NULL;
+
+    opts = qemu_opts_parse_noisily(&qemu_drive_opts, optstr, false);
+    if (!opts) {
+        return;
+    }
+
+    qdict = qemu_opts_to_qdict(opts, NULL);
+
+    if (!qdict_get_try_str(qdict, "node-name")) {
+        error_report("'node-name' needs to be specified");
+        goto out;
+    }
+
+    BlockDriverState *bs = bds_tree_init(qdict, &local_err);
+    if (!bs) {
+        error_report_err(local_err);
+        goto out;
+    }
+
+    QTAILQ_INSERT_TAIL(&monitor_bdrv_states, bs, monitor_list);
+
+out:
+    qemu_opts_del(opts);
+}
+
 void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
 {
     QmpOutputVisitor *ov = qmp_output_visitor_new();
diff --git a/device-hotplug.c b/device-hotplug.c
index 9a7cd66..3e5cdaa 100644
--- a/device-hotplug.c
+++ b/device-hotplug.c
@@ -30,6 +30,7 @@
 #include "qemu/config-file.h"
 #include "sysemu/sysemu.h"
 #include "monitor/monitor.h"
+#include "block/block_int.h"
 
 static DriveInfo *add_init_drive(const char *optstr)
 {
@@ -55,6 +56,12 @@ void hmp_drive_add(Monitor *mon, const QDict *qdict)
 {
     DriveInfo *dinfo = NULL;
     const char *opts = qdict_get_str(qdict, "opts");
+    bool node = qdict_get_try_bool(qdict, "node", false);
+
+    if (node) {
+        hmp_drive_add_node(mon, opts);
+        return;
+    }
 
     dinfo = add_init_drive(opts);
     if (!dinfo) {
diff --git a/hmp-commands.hx b/hmp-commands.hx
index bb52e4d..3b44e52 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1200,8 +1200,8 @@ ETEXI
 
     {
         .name       = "drive_add",
-        .args_type  = "pci_addr:s,opts:s",
-        .params     = "[[<domain>:]<bus>:]<slot>\n"
+        .args_type  = "node:-n,pci_addr:s,opts:s",
+        .params     = "[-n] [[<domain>:]<bus>:]<slot>\n"
                       "[file=file][,if=type][,bus=n]\n"
                       "[,unit=m][,media=d][,index=i]\n"
                       "[,cyls=c,heads=h,secs=s[,trans=t]]\n"
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 9ef823a..dda5ba0 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -694,6 +694,8 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
                   BlockCompletionFunc *cb, void *opaque,
                   BlockJobTxn *txn, Error **errp);
 
+void hmp_drive_add_node(Monitor *mon, const char *optstr);
+
 void blk_set_bs(BlockBackend *blk, BlockDriverState *bs);
 
 void blk_dev_change_media_cb(BlockBackend *blk, bool load);
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH 1/2] hmp: 'drive_add -n' for creating a node without BB

[Max Reitz]

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On 23.02.2016 18:16, Kevin Wolf wrote:
> This patch adds an option to the drive_add HMP command to create only a
> BlockDriverState without a BlockBackend on top.
> 
> The motivation for this is that libvirt needs to specify options to a
> migration target (specifically, detect-zeroes). drive-mirror doesn't
> allow specifying options, and the proper way to do this is to create the
> target BDS separately with blockdev-add (where you can specify options)
> and then use blockdev-mirror to that BDS.
> 
> However, libvirt can't use blockdev-add as long as it is still
> experimental, and we're expecting that it will still take some time, so
> we need to resort to drive_add.
> 
> The problem with drive_add is that so far it always created a BB, and
> BDSes with a BB can't be used as a mirroring target as long as we don't
> support multiple BBs per BDS - and while we're working towards that
> goal, it's another thing that will still take some time.
> 
> So to achieve the goal, the simplest solution to provide the
> functionality now without adding one-off options to the mirror QMP
> commands is to extend drive_add to create nodes without BBs.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  blockdev.c                | 30 ++++++++++++++++++++++++++++++
>  device-hotplug.c          |  7 +++++++
>  hmp-commands.hx           |  4 ++--
>  include/block/block_int.h |  2 ++
>  4 files changed, 41 insertions(+), 2 deletions(-)
> 

Patch looks good to me (well, except for it being a pity we have to fall
back on this HMP command), I only have a minor suggestion:

[...]

> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index bb52e4d..3b44e52 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1200,8 +1200,8 @@ ETEXI
>  
>      {
>          .name       = "drive_add",
> -        .args_type  = "pci_addr:s,opts:s",
> -        .params     = "[[<domain>:]<bus>:]<slot>\n"
> +        .args_type  = "node:-n,pci_addr:s,opts:s",
> +        .params     = "[-n] [[<domain>:]<bus>:]<slot>\n"
>                        "[file=file][,if=type][,bus=n]\n"
>                        "[,unit=m][,media=d][,index=i]\n"
>                        "[,cyls=c,heads=h,secs=s[,trans=t]]\n"

The description reads:

> Add drive to PCI storage controller.

Maybe this should be extended now?

Max


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Re: [Qemu-devel] [PATCH 1/2] hmp: 'drive_add -n' for creating a node without BB

[Kevin Wolf]

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Am 24.02.2016 um 18:50 hat Max Reitz geschrieben:
> On 23.02.2016 18:16, Kevin Wolf wrote:
> > This patch adds an option to the drive_add HMP command to create only a
> > BlockDriverState without a BlockBackend on top.
> > 
> > The motivation for this is that libvirt needs to specify options to a
> > migration target (specifically, detect-zeroes). drive-mirror doesn't
> > allow specifying options, and the proper way to do this is to create the
> > target BDS separately with blockdev-add (where you can specify options)
> > and then use blockdev-mirror to that BDS.
> > 
> > However, libvirt can't use blockdev-add as long as it is still
> > experimental, and we're expecting that it will still take some time, so
> > we need to resort to drive_add.
> > 
> > The problem with drive_add is that so far it always created a BB, and
> > BDSes with a BB can't be used as a mirroring target as long as we don't
> > support multiple BBs per BDS - and while we're working towards that
> > goal, it's another thing that will still take some time.
> > 
> > So to achieve the goal, the simplest solution to provide the
> > functionality now without adding one-off options to the mirror QMP
> > commands is to extend drive_add to create nodes without BBs.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  blockdev.c                | 30 ++++++++++++++++++++++++++++++
> >  device-hotplug.c          |  7 +++++++
> >  hmp-commands.hx           |  4 ++--
> >  include/block/block_int.h |  2 ++
> >  4 files changed, 41 insertions(+), 2 deletions(-)
> > 
> 
> Patch looks good to me (well, except for it being a pity we have to fall
> back on this HMP command), I only have a minor suggestion:
> 
> [...]
> 
> > diff --git a/hmp-commands.hx b/hmp-commands.hx
> > index bb52e4d..3b44e52 100644
> > --- a/hmp-commands.hx
> > +++ b/hmp-commands.hx
> > @@ -1200,8 +1200,8 @@ ETEXI
> >  
> >      {
> >          .name       = "drive_add",
> > -        .args_type  = "pci_addr:s,opts:s",
> > -        .params     = "[[<domain>:]<bus>:]<slot>\n"
> > +        .args_type  = "node:-n,pci_addr:s,opts:s",
> > +        .params     = "[-n] [[<domain>:]<bus>:]<slot>\n"
> >                        "[file=file][,if=type][,bus=n]\n"
> >                        "[,unit=m][,media=d][,index=i]\n"
> >                        "[,cyls=c,heads=h,secs=s[,trans=t]]\n"
> 
> The description reads:
> 
> > Add drive to PCI storage controller.
> 
> Maybe this should be extended now?

It was already wrong before this patch, but I guess I could just add
another patch to the series anyway.

Kevin

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Re: [Qemu-devel] [Qemu-block] [PATCH 1/2] hmp: 'drive_add -n' for creating a node without BB

[Alberto Garcia]

On Tue 23 Feb 2016 06:16:38 PM CET, Kevin Wolf wrote:

> However, libvirt can't use blockdev-add as long as it is still
> experimental, and we're expecting that it will still take some time,
> so we need to resort to drive_add.

But how stable is the HMP API supposed to be?

Berto

Re: [Qemu-devel] [Qemu-block] [PATCH 1/2] hmp: 'drive_add -n' for creating a node without BB

[Eric Blake]

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On 02/25/2016 06:18 AM, Alberto Garcia wrote:
> On Tue 23 Feb 2016 06:16:38 PM CET, Kevin Wolf wrote:
> 
>> However, libvirt can't use blockdev-add as long as it is still
>> experimental, and we're expecting that it will still take some time,
>> so we need to resort to drive_add.
> 
> But how stable is the HMP API supposed to be?

In general, it's not stable. But for this particular API, as long as we
don't have a fully-working QMP replacement, we've been careful to keep
HMP working unchanged.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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[Qemu-devel] [PATCH 2/2] hmp: Extend drive_del to delete nodes without BB

[Kevin Wolf]

Now that we can use drive_add to create new nodes without a BB, we also
want to be able to delete such nodes again.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 blockdev.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index 3f46bc1..b76b6cd 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2816,6 +2816,15 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
     AioContext *aio_context;
     Error *local_err = NULL;
 
+    bs = bdrv_find_node(id);
+    if (bs) {
+        qmp_x_blockdev_del(false, NULL, true, id, &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+        }
+        return;
+    }
+
     blk = blk_by_name(id);
     if (!blk) {
         error_report("Device '%s' not found", id);
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH 2/2] hmp: Extend drive_del to delete nodes without BB

[Max Reitz]

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On 23.02.2016 18:16, Kevin Wolf wrote:
> Now that we can use drive_add to create new nodes without a BB, we also
> want to be able to delete such nodes again.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  blockdev.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 3f46bc1..b76b6cd 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -2816,6 +2816,15 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
>      AioContext *aio_context;
>      Error *local_err = NULL;
>  
> +    bs = bdrv_find_node(id);
> +    if (bs) {
> +        qmp_x_blockdev_del(false, NULL, true, id, &local_err);
> +        if (local_err) {
> +            error_report_err(local_err);
> +        }
> +        return;
> +    }
> +
>      blk = blk_by_name(id);
>      if (!blk) {
>          error_report("Device '%s' not found", id);
> 

It's a bit strange to require the user to specify the node name using
"node-name" for drive_add, but the to use "id" in drive_del; especially
because x-blockdev-del uses "node-name", too.

Up to your discretion.

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [Qemu-devel] [PATCH 2/2] hmp: Extend drive_del to delete nodes without BB

[Kevin Wolf]

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Am 24.02.2016 um 18:54 hat Max Reitz geschrieben:
> On 23.02.2016 18:16, Kevin Wolf wrote:
> > Now that we can use drive_add to create new nodes without a BB, we also
> > want to be able to delete such nodes again.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  blockdev.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/blockdev.c b/blockdev.c
> > index 3f46bc1..b76b6cd 100644
> > --- a/blockdev.c
> > +++ b/blockdev.c
> > @@ -2816,6 +2816,15 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
> >      AioContext *aio_context;
> >      Error *local_err = NULL;
> >  
> > +    bs = bdrv_find_node(id);
> > +    if (bs) {
> > +        qmp_x_blockdev_del(false, NULL, true, id, &local_err);
> > +        if (local_err) {
> > +            error_report_err(local_err);
> > +        }
> > +        return;
> > +    }
> > +
> >      blk = blk_by_name(id);
> >      if (!blk) {
> >          error_report("Device '%s' not found", id);
> > 
> 
> It's a bit strange to require the user to specify the node name using
> "node-name" for drive_add, but the to use "id" in drive_del; especially
> because x-blockdev-del uses "node-name", too.

Not sure I understand. For the user of drive_del that's simply a
positional parameter, so they use neither "id" nor "node-name". Am I
missing something?

Kevin

> Up to your discretion.
> 
> Reviewed-by: Max Reitz <mreitz@redhat.com>
> 



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Re: [Qemu-devel] [PATCH 2/2] hmp: Extend drive_del to delete nodes without BB

[Max Reitz]

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On 24.02.2016 19:23, Kevin Wolf wrote:
> Am 24.02.2016 um 18:54 hat Max Reitz geschrieben:
>> On 23.02.2016 18:16, Kevin Wolf wrote:
>>> Now that we can use drive_add to create new nodes without a BB, we also
>>> want to be able to delete such nodes again.
>>>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>> ---
>>>  blockdev.c | 9 +++++++++
>>>  1 file changed, 9 insertions(+)
>>>
>>> diff --git a/blockdev.c b/blockdev.c
>>> index 3f46bc1..b76b6cd 100644
>>> --- a/blockdev.c
>>> +++ b/blockdev.c
>>> @@ -2816,6 +2816,15 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
>>>      AioContext *aio_context;
>>>      Error *local_err = NULL;
>>>  
>>> +    bs = bdrv_find_node(id);
>>> +    if (bs) {
>>> +        qmp_x_blockdev_del(false, NULL, true, id, &local_err);
>>> +        if (local_err) {
>>> +            error_report_err(local_err);
>>> +        }
>>> +        return;
>>> +    }
>>> +
>>>      blk = blk_by_name(id);
>>>      if (!blk) {
>>>          error_report("Device '%s' not found", id);
>>>
>>
>> It's a bit strange to require the user to specify the node name using
>> "node-name" for drive_add, but the to use "id" in drive_del; especially
>> because x-blockdev-del uses "node-name", too.
> 
> Not sure I understand. For the user of drive_del that's simply a
> positional parameter, so they use neither "id" nor "node-name". Am I
> missing something?

No, it's just me being confused again by the way HMP works. I keep
forgetting that the user doesn't specify the parameter names. So the R-b
stands. :-)

Max


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Re: [Qemu-devel] [PATCH 2/2] hmp: Extend drive_del to delete nodes without BB

[Peter Krempa]

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On Wed, Feb 24, 2016 at 18:54:45 +0100, Max Reitz wrote:
> On 23.02.2016 18:16, Kevin Wolf wrote:
> > Now that we can use drive_add to create new nodes without a BB, we also
> > want to be able to delete such nodes again.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  blockdev.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)

[..]

> > 
> 
> It's a bit strange to require the user to specify the node name using
> "node-name" for drive_add, but the to use "id" in drive_del; especially
> because x-blockdev-del uses "node-name", too.

Well, since 'x-blockdev-del' is considered unstable yet I can't really
use it in libvirt, thus we discussed using drive_del as a workaround.

It makes partially sense since we'd add the new node with 'drive_add' in
the first place.

Peter

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Re: [Qemu-devel] [PATCH 2/2] hmp: Extend drive_del to delete nodes without BB

[Max Reitz]

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On 25.02.2016 13:51, Peter Krempa wrote:
> On Wed, Feb 24, 2016 at 18:54:45 +0100, Max Reitz wrote:
>> On 23.02.2016 18:16, Kevin Wolf wrote:
>>> Now that we can use drive_add to create new nodes without a BB, we also
>>> want to be able to delete such nodes again.
>>>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>> ---
>>>  blockdev.c | 9 +++++++++
>>>  1 file changed, 9 insertions(+)
> 
> [..]
> 
>>>
>>
>> It's a bit strange to require the user to specify the node name using
>> "node-name" for drive_add, but the to use "id" in drive_del; especially
>> because x-blockdev-del uses "node-name", too.
> 
> Well, since 'x-blockdev-del' is considered unstable yet I can't really
> use it in libvirt, thus we discussed using drive_del as a workaround.
> 
> It makes partially sense since we'd add the new node with 'drive_add' in
> the first place.

Yes, you're right. However, my question was solely about the parameter
name (reusing "id" for a node name). As Kevin replied, for HMP the
parameter name doesn't really matter to the user anyway, so reusing the
"id" parameter here is completely fine.

Max


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Re: [Qemu-devel] [PATCH 0/2] block: drive_add/del without BlockBackend

[Kevin Wolf]

Am 23.02.2016 um 18:16 hat Kevin Wolf geschrieben:
> See patch 1 for the detailed description why this is needed. The short
> version is that libvirt needs to enable detect-zeroes on a mirror
> target.
> 
> Peter, can you please check if this provides what you need? I checked
> whether I could do the mirroring operation manually; and if I did it
> right, it looks good to me. (Shortened) protocol of my test:
> [...]

Applied to the block branch.

Kevin