[Qemu-devel] [PATCH v3 0/2] block: formalize and test fleecing

[Qemu-devel] [PATCH v3 0/2] block: formalize and test fleecing

[John Snow]

Formalize the fleecing workflow in patch one,
test that it works in patch two.

V3:
 - Added explicit zero checking as per Eblake's suggestion
 - Remove stale python code

John Snow (2):
  block: allow blockdev-backup from any source
  iotests: add 222 to test basic fleecing

 blockdev.c                 |   2 +-
 tests/qemu-iotests/222     | 152 +++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/222.out |  66 ++++++++++++++++++++
 tests/qemu-iotests/group   |   1 +
 4 files changed, 220 insertions(+), 1 deletion(-)
 create mode 100644 tests/qemu-iotests/222
 create mode 100644 tests/qemu-iotests/222.out

-- 
2.14.4

[Qemu-devel] [PATCH v3 1/2] block: allow blockdev-backup from any source

[John Snow]

In the case of image fleecing, the node we choose as the source
for a blockdev-backup is going to be both a root node AND the
backing node for the exported image. It does not qualify as a root
image in this case.

Loosen the restriction.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 blockdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 58d7570932..526f8b60be 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3517,7 +3517,7 @@ BlockJob *do_blockdev_backup(BlockdevBackup *backup, JobTxn *txn,
         backup->compress = false;
     }
 
-    bs = qmp_get_root_bs(backup->device, errp);
+    bs = bdrv_lookup_bs(backup->device, backup->device, errp);
     if (!bs) {
         return NULL;
     }
-- 
2.14.4

[Qemu-devel] [PATCH v3 2/2] iotests: add 222 to test basic fleecing

[John Snow]

Signed-off-by: John Snow <jsnow@redhat.com>
---
 tests/qemu-iotests/222     | 152 +++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/222.out |  66 ++++++++++++++++++++
 tests/qemu-iotests/group   |   1 +
 3 files changed, 219 insertions(+)
 create mode 100644 tests/qemu-iotests/222
 create mode 100644 tests/qemu-iotests/222.out

diff --git a/tests/qemu-iotests/222 b/tests/qemu-iotests/222
new file mode 100644
index 0000000000..bd84dfa379
--- /dev/null
+++ b/tests/qemu-iotests/222
@@ -0,0 +1,152 @@
+#!/usr/bin/env python
+#
+# This test covers the basic fleecing workflow, which provides a
+# point-in-time snapshot of a node that can be queried over NBD.
+#
+# Copyright (C) 2018 Red Hat, Inc.
+# John helped, too.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# Creator/Owner: John Snow <jsnow@redhat.com>
+
+import iotests
+from iotests import log, qemu_img, qemu_io, qemu_io_silent
+
+iotests.verify_platform(['linux'])
+
+patterns = [("0x5d", "0",         "64k"),
+            ("0xd5", "1M",        "64k"),
+            ("0xdc", "32M",       "64k"),
+            ("0xcd", "0x3ff0000", "64k")]  # 64M - 64K
+
+overwrite = [("0xab", "0",         "64k"), # Full overwrite
+             ("0xad", "0x00f8000", "64k"), # Partial-left (1M-32K)
+             ("0x1d", "0x2008000", "64k"), # Partial-right (32M+32K)
+             ("0xea", "0x3fe0000", "64k")] # Adjacent-left (64M - 128K)
+
+zeroes = [("0", "0x00f8000", "32k"), # Left-end of partial-left (1M-32K)
+          ("0", "0x2010000", "32k"), # Right-end of partial-right (32M+64K)
+          ("0", "0x3fe0000", "64k")] # overwrite[3]
+
+remainder = [("0xd5", "0x108000",  "32k"), # Right-end of partial-left [1]
+             ("0xdc", "32M",       "32k"), # Left-end of partial-right [2]
+             ("0xcd", "0x3ff0000", "64k")] # patterns[3]
+
+with iotests.FilePath('base.img') as base_img_path, \
+     iotests.FilePath('fleece.img') as fleece_img_path, \
+     iotests.FilePath('nbd.sock') as nbd_sock_path, \
+     iotests.VM() as vm:
+
+    log('--- Setting up images ---')
+    log('')
+
+    assert qemu_img('create', '-f', iotests.imgfmt, base_img_path, '64M') == 0
+    assert qemu_img('create', '-f', "qcow2", fleece_img_path, '64M') == 0
+
+    for p in patterns:
+        qemu_io('-c', 'write -P%s %s %s' % p, base_img_path)
+
+    log('Done')
+
+    log('')
+    log('--- Launching VM ---')
+    log('')
+
+    vm.add_drive(base_img_path)
+    vm.launch()
+    log('Done')
+
+    log('')
+    log('--- Setting up Fleecing Graph ---')
+    log('')
+
+    srcNode = "drive0"
+    tgtNode = "fleeceNode"
+
+    # create tgtNode backed by srcNode
+    log(vm.qmp("blockdev-add", **{
+        "driver": "qcow2",
+        "node-name": tgtNode,
+        "file": {
+            "driver": "file",
+            "filename": fleece_img_path,
+        },
+        "backing": srcNode,
+    }))
+
+    # Establish COW from source to fleecing node
+    log(vm.qmp("blockdev-backup",
+               device=srcNode,
+               target=tgtNode,
+               sync="none"))
+
+    log('')
+    log('--- Setting up NBD Export ---')
+    log('')
+
+    nbd_uri = 'nbd+unix:///%s?socket=%s' % (tgtNode, nbd_sock_path)
+    log(vm.qmp("nbd-server-start",
+               **{"addr": { "type": "unix",
+                            "data": { "path": nbd_sock_path } } }))
+
+    log(vm.qmp("nbd-server-add", device=tgtNode))
+
+    log('')
+    log('--- Sanity Check ---')
+    log('')
+
+    for p in (patterns + zeroes):
+        cmd = "read -P%s %s %s" % p
+        log(cmd)
+        assert qemu_io_silent('-r', '-f', 'raw', '-c', cmd, nbd_uri) == 0
+
+    log('')
+    log('--- Testing COW ---')
+    log('')
+
+    for p in overwrite:
+        cmd = "write -P%s %s %s" % p
+        log(cmd)
+        log(vm.hmp_qemu_io(srcNode, cmd))
+
+    log('')
+    log('--- Verifying Data ---')
+    log('')
+
+    for p in (patterns + zeroes):
+        cmd = "read -P%s %s %s" % p
+        log(cmd)
+        assert qemu_io_silent('-r', '-f', 'raw', '-c', cmd, nbd_uri) == 0
+
+    log('')
+    log('--- Cleanup ---')
+    log('')
+
+    log(vm.qmp('block-job-cancel', device=srcNode))
+    log(vm.qmp('nbd-server-stop'))
+    log(vm.qmp('blockdev-del', node_name=tgtNode))
+    vm.shutdown()
+
+    log('')
+    log('--- Confirming writes ---')
+    log('')
+
+    for p in (overwrite + remainder):
+        cmd = "read -P%s %s %s" % p
+        log(cmd)
+        assert qemu_io_silent(base_img_path, '-c', cmd) == 0
+
+    log('')
+    log('Done')
diff --git a/tests/qemu-iotests/222.out b/tests/qemu-iotests/222.out
new file mode 100644
index 0000000000..be925601a8
--- /dev/null
+++ b/tests/qemu-iotests/222.out
@@ -0,0 +1,66 @@
+--- Setting up images ---
+
+Done
+
+--- Launching VM ---
+
+Done
+
+--- Setting up Fleecing Graph ---
+
+{u'return': {}}
+{u'return': {}}
+
+--- Setting up NBD Export ---
+
+{u'return': {}}
+{u'return': {}}
+
+--- Sanity Check ---
+
+read -P0x5d 0 64k
+read -P0xd5 1M 64k
+read -P0xdc 32M 64k
+read -P0xcd 0x3ff0000 64k
+read -P0 0x00f8000 32k
+read -P0 0x2010000 32k
+read -P0 0x3fe0000 64k
+
+--- Testing COW ---
+
+write -P0xab 0 64k
+{u'return': u''}
+write -P0xad 0x00f8000 64k
+{u'return': u''}
+write -P0x1d 0x2008000 64k
+{u'return': u''}
+write -P0xea 0x3fe0000 64k
+{u'return': u''}
+
+--- Verifying Data ---
+
+read -P0x5d 0 64k
+read -P0xd5 1M 64k
+read -P0xdc 32M 64k
+read -P0xcd 0x3ff0000 64k
+read -P0 0x00f8000 32k
+read -P0 0x2010000 32k
+read -P0 0x3fe0000 64k
+
+--- Cleanup ---
+
+{u'return': {}}
+{u'return': {}}
+{u'return': {}}
+
+--- Confirming writes ---
+
+read -P0xab 0 64k
+read -P0xad 0x00f8000 64k
+read -P0x1d 0x2008000 64k
+read -P0xea 0x3fe0000 64k
+read -P0xd5 0x108000 32k
+read -P0xdc 32M 32k
+read -P0xcd 0x3ff0000 64k
+
+Done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index eea75819d2..8019a9f721 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -220,3 +220,4 @@
 218 rw auto quick
 219 rw auto
 221 rw auto quick
+222 rw auto quick
-- 
2.14.4

Re: [Qemu-devel] [PATCH v3 2/2] iotests: add 222 to test basic fleecing

[Eric Blake]

On 06/28/2018 04:25 PM, John Snow wrote:
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>   tests/qemu-iotests/222     | 152 +++++++++++++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/222.out |  66 ++++++++++++++++++++
>   tests/qemu-iotests/group   |   1 +
>   3 files changed, 219 insertions(+)
>   create mode 100644 tests/qemu-iotests/222
>   create mode 100644 tests/qemu-iotests/222.out

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [Qemu-devel] [PATCH v3 2/2] iotests: add 222 to test basic fleecing

[Vladimir Sementsov-Ogievskiy]

29.06.2018 00:25, John Snow wrote:
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>   tests/qemu-iotests/222     | 152 +++++++++++++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/222.out |  66 ++++++++++++++++++++
>   tests/qemu-iotests/group   |   1 +
>   3 files changed, 219 insertions(+)
>   create mode 100644 tests/qemu-iotests/222
>   create mode 100644 tests/qemu-iotests/222.out
>
> diff --git a/tests/qemu-iotests/222 b/tests/qemu-iotests/222
> new file mode 100644
> index 0000000000..bd84dfa379
> --- /dev/null
> +++ b/tests/qemu-iotests/222
> @@ -0,0 +1,152 @@
> +#!/usr/bin/env python
> +#
> +# This test covers the basic fleecing workflow, which provides a
> +# point-in-time snapshot of a node that can be queried over NBD.
> +#
> +# Copyright (C) 2018 Red Hat, Inc.
> +# John helped, too.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 2 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +#
> +# Creator/Owner: John Snow <jsnow@redhat.com>
> +
> +import iotests
> +from iotests import log, qemu_img, qemu_io, qemu_io_silent
> +
> +iotests.verify_platform(['linux'])
> +
> +patterns = [("0x5d", "0",         "64k"),
> +            ("0xd5", "1M",        "64k"),
> +            ("0xdc", "32M",       "64k"),
> +            ("0xcd", "0x3ff0000", "64k")]  # 64M - 64K
> +
> +overwrite = [("0xab", "0",         "64k"), # Full overwrite
> +             ("0xad", "0x00f8000", "64k"), # Partial-left (1M-32K)
> +             ("0x1d", "0x2008000", "64k"), # Partial-right (32M+32K)
> +             ("0xea", "0x3fe0000", "64k")] # Adjacent-left (64M - 128K)
> +
> +zeroes = [("0", "0x00f8000", "32k"), # Left-end of partial-left (1M-32K)
> +          ("0", "0x2010000", "32k"), # Right-end of partial-right (32M+64K)
> +          ("0", "0x3fe0000", "64k")] # overwrite[3]
> +
> +remainder = [("0xd5", "0x108000",  "32k"), # Right-end of partial-left [1]
> +             ("0xdc", "32M",       "32k"), # Left-end of partial-right [2]
> +             ("0xcd", "0x3ff0000", "64k")] # patterns[3]
> +
> +with iotests.FilePath('base.img') as base_img_path, \
> +     iotests.FilePath('fleece.img') as fleece_img_path, \
> +     iotests.FilePath('nbd.sock') as nbd_sock_path, \
> +     iotests.VM() as vm:

Didn't you try use file_path instead like in 209 iotest? It allows 
reduce test indentation to zero.

> +
> +    log('--- Setting up images ---')
> +    log('')
> +
> +    assert qemu_img('create', '-f', iotests.imgfmt, base_img_path, '64M') == 0
> +    assert qemu_img('create', '-f', "qcow2", fleece_img_path, '64M') == 0
> +
> +    for p in patterns:
> +        qemu_io('-c', 'write -P%s %s %s' % p, base_img_path)

don't we need -f iotests.imgfmt here?

> +
> +    log('Done')
> +
> +    log('')
> +    log('--- Launching VM ---')
> +    log('')
> +
> +    vm.add_drive(base_img_path)
> +    vm.launch()
> +    log('Done')
> +
> +    log('')
> +    log('--- Setting up Fleecing Graph ---')
> +    log('')
> +
> +    srcNode = "drive0"
> +    tgtNode = "fleeceNode"

a bit of nit-picking: underscore_style is insisted by PEP8 and even used 
for all other variables here

> +
> +    # create tgtNode backed by srcNode
> +    log(vm.qmp("blockdev-add", **{
> +        "driver": "qcow2",
> +        "node-name": tgtNode,
> +        "file": {
> +            "driver": "file",
> +            "filename": fleece_img_path,
> +        },
> +        "backing": srcNode,
> +    }))
> +
> +    # Establish COW from source to fleecing node
> +    log(vm.qmp("blockdev-backup",
> +               device=srcNode,
> +               target=tgtNode,
> +               sync="none"))
> +
> +    log('')
> +    log('--- Setting up NBD Export ---')
> +    log('')
> +
> +    nbd_uri = 'nbd+unix:///%s?socket=%s' % (tgtNode, nbd_sock_path)
> +    log(vm.qmp("nbd-server-start",
> +               **{"addr": { "type": "unix",
> +                            "data": { "path": nbd_sock_path } } }))
> +
> +    log(vm.qmp("nbd-server-add", device=tgtNode))
> +
> +    log('')
> +    log('--- Sanity Check ---')
> +    log('')
> +
> +    for p in (patterns + zeroes):
> +        cmd = "read -P%s %s %s" % p
> +        log(cmd)
> +        assert qemu_io_silent('-r', '-f', 'raw', '-c', cmd, nbd_uri) == 0
> +
> +    log('')
> +    log('--- Testing COW ---')
> +    log('')
> +
> +    for p in overwrite:
> +        cmd = "write -P%s %s %s" % p
> +        log(cmd)
> +        log(vm.hmp_qemu_io(srcNode, cmd))
> +
> +    log('')
> +    log('--- Verifying Data ---')
> +    log('')
> +
> +    for p in (patterns + zeroes):
> +        cmd = "read -P%s %s %s" % p
> +        log(cmd)
> +        assert qemu_io_silent('-r', '-f', 'raw', '-c', cmd, nbd_uri) == 0
> +
> +    log('')
> +    log('--- Cleanup ---')
> +    log('')
> +
> +    log(vm.qmp('block-job-cancel', device=srcNode))

I think, we should wait for cancelled, like in original test

> +    log(vm.qmp('nbd-server-stop'))
> +    log(vm.qmp('blockdev-del', node_name=tgtNode))
> +    vm.shutdown()
> +
> +    log('')
> +    log('--- Confirming writes ---')
> +    log('')
> +
> +    for p in (overwrite + remainder):
> +        cmd = "read -P%s %s %s" % p
> +        log(cmd)
> +        assert qemu_io_silent(base_img_path, '-c', cmd) == 0
> +
> +    log('')
> +    log('Done')
> diff --git a/tests/qemu-iotests/222.out b/tests/qemu-iotests/222.out
> new file mode 100644
> index 0000000000..be925601a8
> --- /dev/null
> +++ b/tests/qemu-iotests/222.out
> @@ -0,0 +1,66 @@
> +--- Setting up images ---
> +
> +Done
> +
> +--- Launching VM ---
> +
> +Done
> +
> +--- Setting up Fleecing Graph ---
> +
> +{u'return': {}}
> +{u'return': {}}
> +
> +--- Setting up NBD Export ---
> +
> +{u'return': {}}
> +{u'return': {}}
> +
> +--- Sanity Check ---
> +
> +read -P0x5d 0 64k
> +read -P0xd5 1M 64k
> +read -P0xdc 32M 64k
> +read -P0xcd 0x3ff0000 64k
> +read -P0 0x00f8000 32k
> +read -P0 0x2010000 32k
> +read -P0 0x3fe0000 64k
> +
> +--- Testing COW ---
> +
> +write -P0xab 0 64k
> +{u'return': u''}
> +write -P0xad 0x00f8000 64k
> +{u'return': u''}
> +write -P0x1d 0x2008000 64k
> +{u'return': u''}
> +write -P0xea 0x3fe0000 64k
> +{u'return': u''}
> +
> +--- Verifying Data ---
> +
> +read -P0x5d 0 64k
> +read -P0xd5 1M 64k
> +read -P0xdc 32M 64k
> +read -P0xcd 0x3ff0000 64k
> +read -P0 0x00f8000 32k
> +read -P0 0x2010000 32k
> +read -P0 0x3fe0000 64k
> +
> +--- Cleanup ---
> +
> +{u'return': {}}
> +{u'return': {}}
> +{u'return': {}}
> +
> +--- Confirming writes ---
> +
> +read -P0xab 0 64k
> +read -P0xad 0x00f8000 64k
> +read -P0x1d 0x2008000 64k
> +read -P0xea 0x3fe0000 64k
> +read -P0xd5 0x108000 32k
> +read -P0xdc 32M 32k
> +read -P0xcd 0x3ff0000 64k
> +
> +Done
> diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
> index eea75819d2..8019a9f721 100644
> --- a/tests/qemu-iotests/group
> +++ b/tests/qemu-iotests/group
> @@ -220,3 +220,4 @@
>   218 rw auto quick
>   219 rw auto
>   221 rw auto quick
> +222 rw auto quick


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v3 2/2] iotests: add 222 to test basic fleecing

[John Snow]

On 07/02/2018 08:53 AM, Vladimir Sementsov-Ogievskiy wrote:
> 29.06.2018 00:25, John Snow wrote:
>> Signed-off-by: John Snow <jsnow@redhat.com>
>> ---
>>   tests/qemu-iotests/222     | 152
>> +++++++++++++++++++++++++++++++++++++++++++++
>>   tests/qemu-iotests/222.out |  66 ++++++++++++++++++++
>>   tests/qemu-iotests/group   |   1 +
>>   3 files changed, 219 insertions(+)
>>   create mode 100644 tests/qemu-iotests/222
>>   create mode 100644 tests/qemu-iotests/222.out
>>
>> diff --git a/tests/qemu-iotests/222 b/tests/qemu-iotests/222
>> new file mode 100644
>> index 0000000000..bd84dfa379
>> --- /dev/null
>> +++ b/tests/qemu-iotests/222
>> @@ -0,0 +1,152 @@
>> +#!/usr/bin/env python
>> +#
>> +# This test covers the basic fleecing workflow, which provides a
>> +# point-in-time snapshot of a node that can be queried over NBD.
>> +#
>> +# Copyright (C) 2018 Red Hat, Inc.
>> +# John helped, too.
>> +#
>> +# This program is free software; you can redistribute it and/or modify
>> +# it under the terms of the GNU General Public License as published by
>> +# the Free Software Foundation; either version 2 of the License, or
>> +# (at your option) any later version.
>> +#
>> +# This program is distributed in the hope that it will be useful,
>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +# GNU General Public License for more details.
>> +#
>> +# You should have received a copy of the GNU General Public License
>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> +#
>> +# Creator/Owner: John Snow <jsnow@redhat.com>
>> +
>> +import iotests
>> +from iotests import log, qemu_img, qemu_io, qemu_io_silent
>> +
>> +iotests.verify_platform(['linux'])
>> +
>> +patterns = [("0x5d", "0",         "64k"),
>> +            ("0xd5", "1M",        "64k"),
>> +            ("0xdc", "32M",       "64k"),
>> +            ("0xcd", "0x3ff0000", "64k")]  # 64M - 64K
>> +
>> +overwrite = [("0xab", "0",         "64k"), # Full overwrite
>> +             ("0xad", "0x00f8000", "64k"), # Partial-left (1M-32K)
>> +             ("0x1d", "0x2008000", "64k"), # Partial-right (32M+32K)
>> +             ("0xea", "0x3fe0000", "64k")] # Adjacent-left (64M - 128K)
>> +
>> +zeroes = [("0", "0x00f8000", "32k"), # Left-end of partial-left (1M-32K)
>> +          ("0", "0x2010000", "32k"), # Right-end of partial-right
>> (32M+64K)
>> +          ("0", "0x3fe0000", "64k")] # overwrite[3]
>> +
>> +remainder = [("0xd5", "0x108000",  "32k"), # Right-end of
>> partial-left [1]
>> +             ("0xdc", "32M",       "32k"), # Left-end of
>> partial-right [2]
>> +             ("0xcd", "0x3ff0000", "64k")] # patterns[3]
>> +
>> +with iotests.FilePath('base.img') as base_img_path, \
>> +     iotests.FilePath('fleece.img') as fleece_img_path, \
>> +     iotests.FilePath('nbd.sock') as nbd_sock_path, \
>> +     iotests.VM() as vm:
> 
> Didn't you try use file_path instead like in 209 iotest? It allows
> reduce test indentation to zero.
> 

Matter of taste, I guess. It feels weird to see code at the zero indent.

>> +
>> +    log('--- Setting up images ---')
>> +    log('')
>> +
>> +    assert qemu_img('create', '-f', iotests.imgfmt, base_img_path,
>> '64M') == 0
>> +    assert qemu_img('create', '-f', "qcow2", fleece_img_path, '64M')
>> == 0
>> +
>> +    for p in patterns:
>> +        qemu_io('-c', 'write -P%s %s %s' % p, base_img_path)
> 
> don't we need -f iotests.imgfmt here?
> 

Empirically, apparently not. I'll amend it though.

>> +
>> +    log('Done')
>> +
>> +    log('')
>> +    log('--- Launching VM ---')
>> +    log('')
>> +
>> +    vm.add_drive(base_img_path)
>> +    vm.launch()
>> +    log('Done')
>> +
>> +    log('')
>> +    log('--- Setting up Fleecing Graph ---')
>> +    log('')
>> +
>> +    srcNode = "drive0"
>> +    tgtNode = "fleeceNode"
> 
> a bit of nit-picking: underscore_style is insisted by PEP8 and even used
> for all other variables here
> 

I'll change it :(

>> +
>> +    # create tgtNode backed by srcNode
>> +    log(vm.qmp("blockdev-add", **{
>> +        "driver": "qcow2",
>> +        "node-name": tgtNode,
>> +        "file": {
>> +            "driver": "file",
>> +            "filename": fleece_img_path,
>> +        },
>> +        "backing": srcNode,
>> +    }))
>> +
>> +    # Establish COW from source to fleecing node
>> +    log(vm.qmp("blockdev-backup",
>> +               device=srcNode,
>> +               target=tgtNode,
>> +               sync="none"))
>> +
>> +    log('')
>> +    log('--- Setting up NBD Export ---')
>> +    log('')
>> +
>> +    nbd_uri = 'nbd+unix:///%s?socket=%s' % (tgtNode, nbd_sock_path)
>> +    log(vm.qmp("nbd-server-start",
>> +               **{"addr": { "type": "unix",
>> +                            "data": { "path": nbd_sock_path } } }))
>> +
>> +    log(vm.qmp("nbd-server-add", device=tgtNode))
>> +
>> +    log('')
>> +    log('--- Sanity Check ---')
>> +    log('')
>> +
>> +    for p in (patterns + zeroes):
>> +        cmd = "read -P%s %s %s" % p
>> +        log(cmd)
>> +        assert qemu_io_silent('-r', '-f', 'raw', '-c', cmd, nbd_uri)
>> == 0
>> +
>> +    log('')
>> +    log('--- Testing COW ---')
>> +    log('')
>> +
>> +    for p in overwrite:
>> +        cmd = "write -P%s %s %s" % p
>> +        log(cmd)
>> +        log(vm.hmp_qemu_io(srcNode, cmd))
>> +
>> +    log('')
>> +    log('--- Verifying Data ---')
>> +    log('')
>> +
>> +    for p in (patterns + zeroes):
>> +        cmd = "read -P%s %s %s" % p
>> +        log(cmd)
>> +        assert qemu_io_silent('-r', '-f', 'raw', '-c', cmd, nbd_uri)
>> == 0
>> +
>> +    log('')
>> +    log('--- Cleanup ---')
>> +    log('')
>> +
>> +    log(vm.qmp('block-job-cancel', device=srcNode))
> 
> I think, we should wait for cancelled, like in original test
> 

Yes.

>> +    log(vm.qmp('nbd-server-stop'))
>> +    log(vm.qmp('blockdev-del', node_name=tgtNode))
>> +    vm.shutdown()
>> +
>> +    log('')
>> +    log('--- Confirming writes ---')
>> +    log('')
>> +
>> +    for p in (overwrite + remainder):
>> +        cmd = "read -P%s %s %s" % p
>> +        log(cmd)
>> +        assert qemu_io_silent(base_img_path, '-c', cmd) == 0
>> +
>> +    log('')
>> +    log('Done')
>> diff --git a/tests/qemu-iotests/222.out b/tests/qemu-iotests/222.out
>> new file mode 100644
>> index 0000000000..be925601a8
>> --- /dev/null
>> +++ b/tests/qemu-iotests/222.out
>> @@ -0,0 +1,66 @@
>> +--- Setting up images ---
>> +
>> +Done
>> +
>> +--- Launching VM ---
>> +
>> +Done
>> +
>> +--- Setting up Fleecing Graph ---
>> +
>> +{u'return': {}}
>> +{u'return': {}}
>> +
>> +--- Setting up NBD Export ---
>> +
>> +{u'return': {}}
>> +{u'return': {}}
>> +
>> +--- Sanity Check ---
>> +
>> +read -P0x5d 0 64k
>> +read -P0xd5 1M 64k
>> +read -P0xdc 32M 64k
>> +read -P0xcd 0x3ff0000 64k
>> +read -P0 0x00f8000 32k
>> +read -P0 0x2010000 32k
>> +read -P0 0x3fe0000 64k
>> +
>> +--- Testing COW ---
>> +
>> +write -P0xab 0 64k
>> +{u'return': u''}
>> +write -P0xad 0x00f8000 64k
>> +{u'return': u''}
>> +write -P0x1d 0x2008000 64k
>> +{u'return': u''}
>> +write -P0xea 0x3fe0000 64k
>> +{u'return': u''}
>> +
>> +--- Verifying Data ---
>> +
>> +read -P0x5d 0 64k
>> +read -P0xd5 1M 64k
>> +read -P0xdc 32M 64k
>> +read -P0xcd 0x3ff0000 64k
>> +read -P0 0x00f8000 32k
>> +read -P0 0x2010000 32k
>> +read -P0 0x3fe0000 64k
>> +
>> +--- Cleanup ---
>> +
>> +{u'return': {}}
>> +{u'return': {}}
>> +{u'return': {}}
>> +
>> +--- Confirming writes ---
>> +
>> +read -P0xab 0 64k
>> +read -P0xad 0x00f8000 64k
>> +read -P0x1d 0x2008000 64k
>> +read -P0xea 0x3fe0000 64k
>> +read -P0xd5 0x108000 32k
>> +read -P0xdc 32M 32k
>> +read -P0xcd 0x3ff0000 64k
>> +
>> +Done
>> diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
>> index eea75819d2..8019a9f721 100644
>> --- a/tests/qemu-iotests/group
>> +++ b/tests/qemu-iotests/group
>> @@ -220,3 +220,4 @@
>>   218 rw auto quick
>>   219 rw auto
>>   221 rw auto quick
>> +222 rw auto quick
> 
> 

Thanks for the review ... I'll try to make sure some sort of fleecing
workflow patches go in for 3.0. I was hoping your patches wouldn't be
necessary but I think you're making a good argument that they are :(

--js