[Qemu-devel] [PATCH v2 0/2] block/drive-mirror: Check for NULL backing_hd

[Qemu-devel] [PATCH v2 0/2] block/drive-mirror: Check for NULL backing_hd

[Max Reitz]

It should be possible to execute the QMP "drive-mirror" command in
"none" sync mode and "absolute-paths" mode even for block devices
lacking a backing file.

"absolute-paths" does in fact not require a backing file to be present,
as can be seen from the "top" sync mode code path. "top" basically
states that the device should indeed have a backing file - however, the
current code catches the case if it doesn't and then simply treats it as
"full" sync mode, creating a target image without a backing file (in
"absolute-paths" mode). Thus, "absolute-paths" does not imply the target
file must indeed have a backing file.

Therefore, the target file may be left unbacked in case of "none" sync
mode as well, if the specified device is not backed either. Currently,
qemu will crash trying to dereference the backing file pointer since it
assumes that it will always be non-NULL in that case ("none" with
"absolute-paths").

The first patch in this series adds a check whether the specified block
device is backed or not (creating an unbacked target image, if required);
the second patch adds a test case for mirroring unbacked block devices.


Max Reitz (2):
  block/drive-mirror: Check for NULL backing_hd
  qemu-iotests: Add test for unbacked mirroring

 blockdev.c                 |  4 +-
 tests/qemu-iotests/070     | 91 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/070.out | 33 +++++++++++++++++
 tests/qemu-iotests/group   |  1 +
 4 files changed, 127 insertions(+), 2 deletions(-)
 create mode 100755 tests/qemu-iotests/070
 create mode 100644 tests/qemu-iotests/070.out

-- 
1.8.4.2

[Qemu-devel] [PATCH v2 1/2] block/drive-mirror: Check for NULL backing_hd

[Max Reitz]

It should be possible to execute the QMP "drive-mirror" command in
"none" sync mode and "absolute-paths" mode even for block devices
lacking a backing file.

"absolute-paths" does in fact not require a backing file to be present,
as can be seen from the "top" sync mode code path. "top" basically
states that the device should indeed have a backing file - however, the
current code catches the case if it doesn't and then simply treats it as
"full" sync mode, creating a target image without a backing file (in
"absolute-paths" mode). Thus, "absolute-paths" does not imply the target
file must indeed have a backing file.

Therefore, the target file may be left unbacked in case of "none" sync
mode as well, if the specified device is not backed either. Currently,
qemu will crash trying to dereference the backing file pointer since it
assumes that it will always be non-NULL in that case ("none" with
"absolute-paths").

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 blockdev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index b260477..986e59d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2038,8 +2038,8 @@ void qmp_drive_mirror(const char *device, const char *target,
         case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
             /* create new image with backing file */
             bdrv_img_create(target, format,
-                            source->filename,
-                            source->drv->format_name,
+                            source ? source->filename : NULL,
+                            source ? source->drv->format_name : NULL,
                             NULL, size, flags, &local_err, false);
             break;
         default:
-- 
1.8.4.2

[Qemu-devel] [PATCH v2 2/2] qemu-iotests: Add test for unbacked mirroring

[Max Reitz]

Add a new test for mirroring unbacked images in "absolute-paths" mode.
This should work, if possible, but most importantly, qemu should never
crash.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 tests/qemu-iotests/070     | 91 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/070.out | 33 +++++++++++++++++
 tests/qemu-iotests/group   |  1 +
 3 files changed, 125 insertions(+)
 create mode 100755 tests/qemu-iotests/070
 create mode 100644 tests/qemu-iotests/070.out

diff --git a/tests/qemu-iotests/070 b/tests/qemu-iotests/070
new file mode 100755
index 0000000..25ecf99
--- /dev/null
+++ b/tests/qemu-iotests/070
@@ -0,0 +1,91 @@
+#!/bin/bash
+#
+# Test mirroring block device without backing file in absolute-paths mode
+#
+# Copyright (C) 2013 Red Hat, Inc.
+#
+# 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=mreitz@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qed qcow2 qcow2 vmdk
+_supported_proto file
+_supported_os Linux
+
+function do_run_qemu()
+{
+    echo Testing: "$@" | _filter_imgfmt
+    $QEMU -nographic -qmp stdio -serial none "$@"
+    echo
+}
+
+function run_qemu()
+{
+    # Filter out empty returns and the SHUTDOWN event, because these may occur
+    # interleaved with the block job events (in a non-deterministic manner).
+    # Also, filter out the "Formatting" message which is emitted when the target
+    # image is created - it contains format-specific information.
+    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qmp |\
+        grep -v '{"return": {}}' | grep -v '"event": "SHUTDOWN"' |\
+        grep -v '^Formatting'
+}
+
+size=128K
+
+_make_test_img $size
+
+for sync in full top none
+do
+
+echo
+echo "=== Mirroring non-backed image in absolute-paths mode with sync=$sync ==="
+echo
+
+run_qemu -drive file="$TEST_IMG",format="$IMGFMT",if=none,id=disk \
+         -device virtio-blk-pci,drive=disk,id=virtio0 <<EOF
+{ "execute": "qmp_capabilities" }
+{ "execute": "drive-mirror",
+    "arguments": { "device": "disk", "target": "$TEST_IMG.target",
+                   "format": "$IMGFMT", "mode": "absolute-paths",
+                   "sync": "$sync" } }
+{ "execute": "quit" }
+EOF
+
+rm -f $TEST_IMG.target
+
+done
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/070.out b/tests/qemu-iotests/070.out
new file mode 100644
index 0000000..246b0f1
--- /dev/null
+++ b/tests/qemu-iotests/070.out
@@ -0,0 +1,33 @@
+QA output created by 070
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 
+
+=== Mirroring non-backed image in absolute-paths mode with sync=full ===
+
+Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
+QMP_VERSION
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
+
+
+=== Mirroring non-backed image in absolute-paths mode with sync=top ===
+
+Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
+QMP_VERSION
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
+
+
+=== Mirroring non-backed image in absolute-paths mode with sync=none ===
+
+Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
+QMP_VERSION
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
+
+*** done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index c57ff35..b18b241 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -75,3 +75,4 @@
 067 rw auto
 068 rw auto
 069 rw auto
+070 rw auto
-- 
1.8.4.2

Re: [Qemu-devel] [PATCH v2 1/2] block/drive-mirror: Check for NULL backing_hd

[Fam Zheng]

On 11/05/2013 08:35 AM, Max Reitz wrote:
> It should be possible to execute the QMP "drive-mirror" command in
> "none" sync mode and "absolute-paths" mode even for block devices
> lacking a backing file.
>
> "absolute-paths" does in fact not require a backing file to be present,
> as can be seen from the "top" sync mode code path. "top" basically
> states that the device should indeed have a backing file - however, the
> current code catches the case if it doesn't and then simply treats it as
> "full" sync mode, creating a target image without a backing file (in
> "absolute-paths" mode). Thus, "absolute-paths" does not imply the target
> file must indeed have a backing file.
>
> Therefore, the target file may be left unbacked in case of "none" sync
> mode as well, if the specified device is not backed either. Currently,
> qemu will crash trying to dereference the backing file pointer since it
> assumes that it will always be non-NULL in that case ("none" with
> "absolute-paths").
>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>   blockdev.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/blockdev.c b/blockdev.c
> index b260477..986e59d 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -2038,8 +2038,8 @@ void qmp_drive_mirror(const char *device, const char *target,
>           case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
>               /* create new image with backing file */
>               bdrv_img_create(target, format,
> -                            source->filename,
> -                            source->drv->format_name,
> +                            source ? source->filename : NULL,
> +                            source ? source->drv->format_name : NULL,
>                               NULL, size, flags, &local_err, false);
>               break;
>           default:
The code around here is:

2029     if (sync == MIRROR_SYNC_MODE_FULL && mode != 
NEW_IMAGE_MODE_EXISTING) {
2030         /* create new image w/o backing file */
2031         assert(format && drv);
2032         bdrv_img_create(target, format,
2033                         NULL, NULL, NULL, size, flags, &local_err, 
false);
2034     } else {
2035         switch (mode) {
2036         case NEW_IMAGE_MODE_EXISTING:
2037             break;
2038         case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
2039             /* create new image with backing file */
2040             bdrv_img_create(target, format,
2041                             source->filename,
2042                             source->drv->format_name,
2043                             NULL, size, flags, &local_err, false);
2044             break;
2045         default:
2046             abort();
2047         }
2048     }

Why not update the if condition and reuse the branch, I think this is a 
better branching? Either should be fine, but in your change you should 
also update the comment in line 2039.

Thanks,
Fam

Re: [Qemu-devel] [PATCH v2 2/2] qemu-iotests: Add test for unbacked mirroring

[Wenchao Xia]

于 2013/11/5 8:35, Max Reitz 写道:
> Add a new test for mirroring unbacked images in "absolute-paths" mode.
> This should work, if possible, but most importantly, qemu should never
> crash.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>   tests/qemu-iotests/070     | 91 ++++++++++++++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/070.out | 33 +++++++++++++++++
>   tests/qemu-iotests/group   |  1 +
>   3 files changed, 125 insertions(+)
>   create mode 100755 tests/qemu-iotests/070
>   create mode 100644 tests/qemu-iotests/070.out
> 
> diff --git a/tests/qemu-iotests/070 b/tests/qemu-iotests/070
> new file mode 100755
> index 0000000..25ecf99
> --- /dev/null
> +++ b/tests/qemu-iotests/070
> @@ -0,0 +1,91 @@
> +#!/bin/bash
> +#
> +# Test mirroring block device without backing file in absolute-paths mode
> +#
> +# Copyright (C) 2013 Red Hat, Inc.
> +#
> +# 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=mreitz@redhat.com
> +
> +seq="$(basename $0)"
> +echo "QA output created by $seq"
> +
> +here="$PWD"
> +tmp=/tmp/$$
> +status=1	# failure is the default!
> +
> +_cleanup()
> +{
> +	_cleanup_test_img
> +}
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +# get standard environment, filters and checks
> +. ./common.rc
> +. ./common.filter
> +
> +_supported_fmt qed qcow2 qcow2 vmdk
> +_supported_proto file
> +_supported_os Linux
> +
> +function do_run_qemu()
> +{
> +    echo Testing: "$@" | _filter_imgfmt
> +    $QEMU -nographic -qmp stdio -serial none "$@"
> +    echo
> +}
> +
> +function run_qemu()
> +{
> +    # Filter out empty returns and the SHUTDOWN event, because these may occur
> +    # interleaved with the block job events (in a non-deterministic manner).
> +    # Also, filter out the "Formatting" message which is emitted when the target
> +    # image is created - it contains format-specific information.
> +    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qmp |\
> +        grep -v '{"return": {}}' | grep -v '"event": "SHUTDOWN"' |\
> +        grep -v '^Formatting'
> +}
> +
> +size=128K
> +
> +_make_test_img $size
> +
> +for sync in full top none
> +do
> +
> +echo
> +echo "=== Mirroring non-backed image in absolute-paths mode with sync=$sync ==="
> +echo
> +
> +run_qemu -drive file="$TEST_IMG",format="$IMGFMT",if=none,id=disk \
> +         -device virtio-blk-pci,drive=disk,id=virtio0 <<EOF
> +{ "execute": "qmp_capabilities" }
> +{ "execute": "drive-mirror",
> +    "arguments": { "device": "disk", "target": "$TEST_IMG.target",
> +                   "format": "$IMGFMT", "mode": "absolute-paths",
> +                   "sync": "$sync" } }
> +{ "execute": "quit" }
> +EOF
> +
> +rm -f $TEST_IMG.target
> +
> +done
> +
> +# success, all done
> +echo "*** done"
> +rm -f $seq.full
> +status=0
> diff --git a/tests/qemu-iotests/070.out b/tests/qemu-iotests/070.out
> new file mode 100644
> index 0000000..246b0f1
> --- /dev/null
> +++ b/tests/qemu-iotests/070.out
> @@ -0,0 +1,33 @@
> +QA output created by 070
> +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
> +
> +=== Mirroring non-backed image in absolute-paths mode with sync=full ===
> +
> +Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
> +QMP_VERSION
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
> +
> +
> +=== Mirroring non-backed image in absolute-paths mode with sync=top ===
> +
> +Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
> +QMP_VERSION
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
> +
> +
> +=== Mirroring non-backed image in absolute-paths mode with sync=none ===
> +
> +Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
> +QMP_VERSION
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
> +
> +*** done
> diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
> index c57ff35..b18b241 100644
> --- a/tests/qemu-iotests/group
> +++ b/tests/qemu-iotests/group
> @@ -75,3 +75,4 @@
>   067 rw auto
>   068 rw auto
>   069 rw auto
> +070 rw auto
> 
  The code seems fine, but why not use python code as 056? I think for
cases that need start qemu, python is better since the infras is ready
and easier to talk with qmp protocol.

Re: [Qemu-devel] [PATCH v2 0/2] block/drive-mirror: Check for NULL backing_hd

[Paolo Bonzini]

Il 05/11/2013 01:35, Max Reitz ha scritto:
> It should be possible to execute the QMP "drive-mirror" command in
> "none" sync mode and "absolute-paths" mode even for block devices
> lacking a backing file.
> 
> "absolute-paths" does in fact not require a backing file to be present,
> as can be seen from the "top" sync mode code path. "top" basically
> states that the device should indeed have a backing file - however, the
> current code catches the case if it doesn't and then simply treats it as
> "full" sync mode, creating a target image without a backing file (in
> "absolute-paths" mode). Thus, "absolute-paths" does not imply the target
> file must indeed have a backing file.
> 
> Therefore, the target file may be left unbacked in case of "none" sync
> mode as well, if the specified device is not backed either. Currently,
> qemu will crash trying to dereference the backing file pointer since it
> assumes that it will always be non-NULL in that case ("none" with
> "absolute-paths").
> 
> The first patch in this series adds a check whether the specified block
> device is backed or not (creating an unbacked target image, if required);
> the second patch adds a test case for mirroring unbacked block devices.
> 
> 
> Max Reitz (2):
>   block/drive-mirror: Check for NULL backing_hd
>   qemu-iotests: Add test for unbacked mirroring
> 
>  blockdev.c                 |  4 +-
>  tests/qemu-iotests/070     | 91 ++++++++++++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/070.out | 33 +++++++++++++++++
>  tests/qemu-iotests/group   |  1 +
>  4 files changed, 127 insertions(+), 2 deletions(-)
>  create mode 100755 tests/qemu-iotests/070
>  create mode 100644 tests/qemu-iotests/070.out
> 

Patch 1 is fine.

For patch 2, there are existing drive-mirror tests written in Python.
I'll let the maintainers whether they are fine with a new test, or
prefer to extend those with a new testcase.

Paolo

Re: [Qemu-devel] [PATCH v2 1/2] block/drive-mirror: Check for NULL backing_hd

[Max Reitz]

On 05.11.2013 04:32, Fam Zheng wrote:
>
> On 11/05/2013 08:35 AM, Max Reitz wrote:
>> It should be possible to execute the QMP "drive-mirror" command in
>> "none" sync mode and "absolute-paths" mode even for block devices
>> lacking a backing file.
>>
>> "absolute-paths" does in fact not require a backing file to be present,
>> as can be seen from the "top" sync mode code path. "top" basically
>> states that the device should indeed have a backing file - however, the
>> current code catches the case if it doesn't and then simply treats it as
>> "full" sync mode, creating a target image without a backing file (in
>> "absolute-paths" mode). Thus, "absolute-paths" does not imply the target
>> file must indeed have a backing file.
>>
>> Therefore, the target file may be left unbacked in case of "none" sync
>> mode as well, if the specified device is not backed either. Currently,
>> qemu will crash trying to dereference the backing file pointer since it
>> assumes that it will always be non-NULL in that case ("none" with
>> "absolute-paths").
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   blockdev.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/blockdev.c b/blockdev.c
>> index b260477..986e59d 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -2038,8 +2038,8 @@ void qmp_drive_mirror(const char *device, const
>> char *target,
>>           case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
>>               /* create new image with backing file */
>>               bdrv_img_create(target, format,
>> -                            source->filename,
>> -                            source->drv->format_name,
>> +                            source ? source->filename : NULL,
>> +                            source ? source->drv->format_name : NULL,
>>                               NULL, size, flags, &local_err, false);
>>               break;
>>           default:
> The code around here is:
>
> 2029     if (sync == MIRROR_SYNC_MODE_FULL && mode !=
> NEW_IMAGE_MODE_EXISTING) {
> 2030         /* create new image w/o backing file */
> 2031         assert(format && drv);
> 2032         bdrv_img_create(target, format,
> 2033                         NULL, NULL, NULL, size, flags,
> &local_err, false);
> 2034     } else {
> 2035         switch (mode) {
> 2036         case NEW_IMAGE_MODE_EXISTING:
> 2037             break;
> 2038         case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
> 2039             /* create new image with backing file */
> 2040             bdrv_img_create(target, format,
> 2041                             source->filename,
> 2042                             source->drv->format_name,
> 2043                             NULL, size, flags, &local_err, false);
> 2044             break;
> 2045         default:
> 2046             abort();
> 2047         }
> 2048     }
>
> Why not update the if condition and reuse the branch, I think this is
> a better branching? Either should be fine, but in your change you
> should also update the comment in line 2039.

Okay, I'll go for updating the condition.

Max

> Thanks,
> Fam

Re: [Qemu-devel] [PATCH v2 2/2] qemu-iotests: Add test for unbacked mirroring

[Max Reitz]

On 05.11.2013 10:00, Wenchao Xia wrote:
> 于 2013/11/5 8:35, Max Reitz 写道:
>> Add a new test for mirroring unbacked images in "absolute-paths" mode.
>> This should work, if possible, but most importantly, qemu should never
>> crash.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   tests/qemu-iotests/070     | 91 ++++++++++++++++++++++++++++++++++++++++++++++
>>   tests/qemu-iotests/070.out | 33 +++++++++++++++++
>>   tests/qemu-iotests/group   |  1 +
>>   3 files changed, 125 insertions(+)
>>   create mode 100755 tests/qemu-iotests/070
>>   create mode 100644 tests/qemu-iotests/070.out
>>
>> diff --git a/tests/qemu-iotests/070 b/tests/qemu-iotests/070
>> new file mode 100755
>> index 0000000..25ecf99
>> --- /dev/null
>> +++ b/tests/qemu-iotests/070
>> @@ -0,0 +1,91 @@
>> +#!/bin/bash
>> +#
>> +# Test mirroring block device without backing file in absolute-paths mode
>> +#
>> +# Copyright (C) 2013 Red Hat, Inc.
>> +#
>> +# 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=mreitz@redhat.com
>> +
>> +seq="$(basename $0)"
>> +echo "QA output created by $seq"
>> +
>> +here="$PWD"
>> +tmp=/tmp/$$
>> +status=1	# failure is the default!
>> +
>> +_cleanup()
>> +{
>> +	_cleanup_test_img
>> +}
>> +trap "_cleanup; exit \$status" 0 1 2 3 15
>> +
>> +# get standard environment, filters and checks
>> +. ./common.rc
>> +. ./common.filter
>> +
>> +_supported_fmt qed qcow2 qcow2 vmdk
>> +_supported_proto file
>> +_supported_os Linux
>> +
>> +function do_run_qemu()
>> +{
>> +    echo Testing: "$@" | _filter_imgfmt
>> +    $QEMU -nographic -qmp stdio -serial none "$@"
>> +    echo
>> +}
>> +
>> +function run_qemu()
>> +{
>> +    # Filter out empty returns and the SHUTDOWN event, because these may occur
>> +    # interleaved with the block job events (in a non-deterministic manner).
>> +    # Also, filter out the "Formatting" message which is emitted when the target
>> +    # image is created - it contains format-specific information.
>> +    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qmp |\
>> +        grep -v '{"return": {}}' | grep -v '"event": "SHUTDOWN"' |\
>> +        grep -v '^Formatting'
>> +}
>> +
>> +size=128K
>> +
>> +_make_test_img $size
>> +
>> +for sync in full top none
>> +do
>> +
>> +echo
>> +echo "=== Mirroring non-backed image in absolute-paths mode with sync=$sync ==="
>> +echo
>> +
>> +run_qemu -drive file="$TEST_IMG",format="$IMGFMT",if=none,id=disk \
>> +         -device virtio-blk-pci,drive=disk,id=virtio0 <<EOF
>> +{ "execute": "qmp_capabilities" }
>> +{ "execute": "drive-mirror",
>> +    "arguments": { "device": "disk", "target": "$TEST_IMG.target",
>> +                   "format": "$IMGFMT", "mode": "absolute-paths",
>> +                   "sync": "$sync" } }
>> +{ "execute": "quit" }
>> +EOF
>> +
>> +rm -f $TEST_IMG.target
>> +
>> +done
>> +
>> +# success, all done
>> +echo "*** done"
>> +rm -f $seq.full
>> +status=0
>> diff --git a/tests/qemu-iotests/070.out b/tests/qemu-iotests/070.out
>> new file mode 100644
>> index 0000000..246b0f1
>> --- /dev/null
>> +++ b/tests/qemu-iotests/070.out
>> @@ -0,0 +1,33 @@
>> +QA output created by 070
>> +Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
>> +
>> +=== Mirroring non-backed image in absolute-paths mode with sync=full ===
>> +
>> +Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
>> +QMP_VERSION
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
>> +
>> +
>> +=== Mirroring non-backed image in absolute-paths mode with sync=top ===
>> +
>> +Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
>> +QMP_VERSION
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
>> +
>> +
>> +=== Mirroring non-backed image in absolute-paths mode with sync=none ===
>> +
>> +Testing: -drive file=TEST_DIR/t.IMGFMT,format=IMGFMT,if=none,id=disk -device virtio-blk-pci,drive=disk,id=virtio0
>> +QMP_VERSION
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 131072, "offset": 131072, "speed": 0, "type": "mirror"}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "ide1-cd0", "tray-open": true}}
>> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "DEVICE_TRAY_MOVED", "data": {"device": "floppy0", "tray-open": true}}
>> +
>> +*** done
>> diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
>> index c57ff35..b18b241 100644
>> --- a/tests/qemu-iotests/group
>> +++ b/tests/qemu-iotests/group
>> @@ -75,3 +75,4 @@
>>   067 rw auto
>>   068 rw auto
>>   069 rw auto
>> +070 rw auto
>>
>   The code seems fine, but why not use python code as 056? I think for
> cases that need start qemu, python is better since the infras is ready
> and easier to talk with qmp protocol.

Creating a bash script is so much easier. ;-)

But, yes, you're right, a python script is probably the better way to
go. I'll also take a look whether I can extend a current test case
instead (as Paolo suggested).

Max