[Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Stefan Hajnoczi]

Commit 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce
vm_shutdown()") added a bdrv_drain_all() call.  As a side-effect of the
drain operation the block job iterates one more time than before.  The
185 output no longer matches and the test is failing now.

It may be possible to avoid the superfluous block job iteration, but
that type of patch is not suitable late in the QEMU 2.12 release cycle.

This patch simply updates the 185 output file.  The new behavior is
correct, just not optimal, so make the test pass again.

Fixes: 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce vm_shutdown()")
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: QingFeng Hao <haoqf@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/185     | 10 ++++++----
 tests/qemu-iotests/185.out | 12 +++++++-----
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/tests/qemu-iotests/185 b/tests/qemu-iotests/185
index f5b47e4c1a..298d88d04e 100755
--- a/tests/qemu-iotests/185
+++ b/tests/qemu-iotests/185
@@ -92,9 +92,8 @@ echo === Start commit job and exit qemu ===
 echo
 
 # Note that the reference output intentionally includes the 'offset' field in
-# BLOCK_JOB_CANCELLED events for all of the following block jobs. They are
-# predictable and any change in the offsets would hint at a bug in the job
-# throttling code.
+# BLOCK_JOB_* events for all of the following block jobs. They are predictable
+# and any change in the offsets would hint at a bug in the job throttling code.
 #
 # In order to achieve these predictable offsets, all of the following tests
 # use speed=65536. Each job will perform exactly one iteration before it has
@@ -102,11 +101,14 @@ echo
 # command to be received (after receiving the command, the rest runs
 # synchronously, so jobs can arbitrarily continue or complete).
 #
+# Jobs present while QEMU is terminating iterate once more due to
+# bdrv_drain_all().
+#
 # The buffer size for commit and streaming is 512k (waiting for 8 seconds after
 # the first request), for active commit and mirror it's large enough to cover
 # the full 4M, and for backup it's the qcow2 cluster size, which we know is
 # 64k. As all of these are at least as large as the speed, we are sure that the
-# offset doesn't advance after the first iteration before qemu exits.
+# offset advances exactly twice before qemu exits.
 
 _send_qemu_cmd $h \
     "{ 'execute': 'block-commit',
diff --git a/tests/qemu-iotests/185.out b/tests/qemu-iotests/185.out
index 57eaf8d699..2c4b04de73 100644
--- a/tests/qemu-iotests/185.out
+++ b/tests/qemu-iotests/185.out
@@ -20,7 +20,7 @@ Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 backing_file=TEST_DIR/t.q
 {"return": {}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false}}
-{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 67108864, "offset": 524288, "speed": 65536, "type": "commit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 67108864, "offset": 1048576, "speed": 65536, "type": "commit"}}
 
 === Start active commit job and exit qemu ===
 
@@ -28,16 +28,18 @@ Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 backing_file=TEST_DIR/t.q
 {"return": {}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false}}
-{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 4194304, "offset": 4194304, "speed": 65536, "type": "commit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 4194304, "offset": 4194304, "speed": 65536, "type": "commit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 4194304, "offset": 4194304, "speed": 65536, "type": "commit"}}
 
 === Start mirror job and exit qemu ===
 
 {"return": {}}
 Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 size=67108864 cluster_size=65536 lazy_refcounts=off refcount_bits=16
 {"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 4194304, "offset": 4194304, "speed": 65536, "type": "mirror"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false}}
-{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 4194304, "offset": 4194304, "speed": 65536, "type": "mirror"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len": 4194304, "offset": 4194304, "speed": 65536, "type": "mirror"}}
 
 === Start backup job and exit qemu ===
 
@@ -46,7 +48,7 @@ Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 size=67108864 cluster_size=65536 l
 {"return": {}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false}}
-{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 67108864, "offset": 65536, "speed": 65536, "type": "backup"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 67108864, "offset": 131072, "speed": 65536, "type": "backup"}}
 
 === Start streaming job and exit qemu ===
 
@@ -54,6 +56,6 @@ Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 size=67108864 cluster_size=65536 l
 {"return": {}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false}}
-{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 67108864, "offset": 524288, "speed": 65536, "type": "stream"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "disk", "len": 67108864, "offset": 1048576, "speed": 65536, "type": "stream"}}
 No errors were found on the image.
 *** done
-- 
2.14.3

Re: [Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Eric Blake]

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On 04/04/2018 10:01 AM, Stefan Hajnoczi wrote:
> Commit 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce
> vm_shutdown()") added a bdrv_drain_all() call.  As a side-effect of the
> drain operation the block job iterates one more time than before.  The
> 185 output no longer matches and the test is failing now.
> 
> It may be possible to avoid the superfluous block job iteration, but
> that type of patch is not suitable late in the QEMU 2.12 release cycle.
> 
> This patch simply updates the 185 output file.  The new behavior is
> correct, just not optimal, so make the test pass again.
> 
> Fixes: 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce vm_shutdown()")
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: QingFeng Hao <haoqf@linux.vnet.ibm.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  tests/qemu-iotests/185     | 10 ++++++----
>  tests/qemu-iotests/185.out | 12 +++++++-----
>  2 files changed, 13 insertions(+), 9 deletions(-)

> @@ -102,11 +101,14 @@ echo
>  # command to be received (after receiving the command, the rest runs
>  # synchronously, so jobs can arbitrarily continue or complete).
>  #
> +# Jobs present while QEMU is terminating iterate once more due to
> +# bdrv_drain_all().

Do we want to add something like: "FIXME: removing the bdrv_drain_all()
may be desirable in a future patch; and would warrant a change to the
expected output."?  Either way,

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

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


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Re: [Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Max Reitz]

On 2018-04-04 17:01, Stefan Hajnoczi wrote:
> Commit 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce
> vm_shutdown()") added a bdrv_drain_all() call.  As a side-effect of the
> drain operation the block job iterates one more time than before.  The
> 185 output no longer matches and the test is failing now.
> 
> It may be possible to avoid the superfluous block job iteration, but
> that type of patch is not suitable late in the QEMU 2.12 release cycle.
> 
> This patch simply updates the 185 output file.  The new behavior is
> correct, just not optimal, so make the test pass again.
> 
> Fixes: 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce vm_shutdown()")
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: QingFeng Hao <haoqf@linux.vnet.ibm.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  tests/qemu-iotests/185     | 10 ++++++----
>  tests/qemu-iotests/185.out | 12 +++++++-----
>  2 files changed, 13 insertions(+), 9 deletions(-)

On tmpfs, this isn't enough to let the test pass.  There, the active
commit job finishes before the quit is sent, resulting in this diff:

--- tests/qemu-iotests/185.out      2018-04-04 18:10:02.015935435 +0200
+++ tests/qemu-iotests/185.out.bad  2018-04-04 18:10:21.045473817 +0200
@@ -26,9 +26,9 @@

 {"return": {}}
 {"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
"event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 4194304,
"offset": 4194304, "speed": 65536, "type": "commit"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
"event": "SHUTDOWN", "data": {"guest": false}}
-{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
"event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 4194304,
"offset": 4194304, "speed": 65536, "type": "commit"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
"event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len":
4194304, "offset": 4194304, "speed": 65536, "type": "commit"}}

 === Start mirror job and exit qemu ===

This seems to be independent of whether there is actually data on
TEST_IMG (the commit source), so something doesn't seem quite right with
the block job throttling here...?

Max

Re: [Qemu-devel] [Qemu-block] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Stefan Hajnoczi]

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On Wed, Apr 04, 2018 at 06:16:12PM +0200, Max Reitz wrote:
> On 2018-04-04 17:01, Stefan Hajnoczi wrote:
> > Commit 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce
> > vm_shutdown()") added a bdrv_drain_all() call.  As a side-effect of the
> > drain operation the block job iterates one more time than before.  The
> > 185 output no longer matches and the test is failing now.
> > 
> > It may be possible to avoid the superfluous block job iteration, but
> > that type of patch is not suitable late in the QEMU 2.12 release cycle.
> > 
> > This patch simply updates the 185 output file.  The new behavior is
> > correct, just not optimal, so make the test pass again.
> > 
> > Fixes: 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce vm_shutdown()")
> > Cc: Kevin Wolf <kwolf@redhat.com>
> > Cc: QingFeng Hao <haoqf@linux.vnet.ibm.com>
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  tests/qemu-iotests/185     | 10 ++++++----
> >  tests/qemu-iotests/185.out | 12 +++++++-----
> >  2 files changed, 13 insertions(+), 9 deletions(-)
> 
> On tmpfs, this isn't enough to let the test pass.  There, the active
> commit job finishes before the quit is sent, resulting in this diff:
> 
> --- tests/qemu-iotests/185.out      2018-04-04 18:10:02.015935435 +0200
> +++ tests/qemu-iotests/185.out.bad  2018-04-04 18:10:21.045473817 +0200
> @@ -26,9 +26,9 @@
> 
>  {"return": {}}
>  {"return": {}}
> +{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
> "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 4194304,
> "offset": 4194304, "speed": 65536, "type": "commit"}}
>  {"return": {}}
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
> "event": "SHUTDOWN", "data": {"guest": false}}
> -{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
> "event": "BLOCK_JOB_READY", "data": {"device": "disk", "len": 4194304,
> "offset": 4194304, "speed": 65536, "type": "commit"}}
>  {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP},
> "event": "BLOCK_JOB_COMPLETED", "data": {"device": "disk", "len":
> 4194304, "offset": 4194304, "speed": 65536, "type": "commit"}}
> 
>  === Start mirror job and exit qemu ===
> 
> This seems to be independent of whether there is actually data on
> TEST_IMG (the commit source), so something doesn't seem quite right with
> the block job throttling here...?

That is a race condition.  I can reproduce it on XFS too.

Will see if I can figure it out...

Stefan

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Re: [Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Stefan Hajnoczi]

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On Wed, Apr 04, 2018 at 06:16:12PM +0200, Max Reitz wrote:
> On 2018-04-04 17:01, Stefan Hajnoczi wrote:
>  === Start mirror job and exit qemu ===
> 
> This seems to be independent of whether there is actually data on
> TEST_IMG (the commit source), so something doesn't seem quite right with
> the block job throttling here...?

I've been playing around with this test failure.  Let's leave it broken
(!) in QEMU 2.12 because this test has uncovered a block job ratelimit
issue that's not a regression.  The fix shouldn't be rushed.

block/mirror.c calculates delay_ns but then discards it:

  static void coroutine_fn mirror_run(void *opaque)
  {
      ...

      for (;;) {
          ...delay_ns is calculated based on job speed...

          ret = 0;
          trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
          if (block_job_is_cancelled(&s->common) && s->common.force) {
              break;
          } else if (!should_complete) {
              delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
	        ^--- we discard it!
              block_job_sleep_ns(&s->common, delay_ns);
          }
          s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
      }

      ...
  }

This is why the mirror-based tests are completing even though we'd
expect them to only reach the "next" iteration due to the job speed.

Increasing the 4 MB write operation in the test to >16 MB (the mirror
buffer size) doesn't solve the problem because the next QMP command will
race with the job's 0 ns sleep.  It would just make the test unreliable.

I'll work on the following for QEMU 2.13:

1. Avoid spurious block_job_enter() from block_job_drain().  This
   eliminates the extra block job iteration that changed the output in
   the first place.

2. Honor the job speed in block/mirror.c.

The end result will be that the test output will not require changes.

Stefan

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Re: [Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Kevin Wolf]

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Am 10.04.2018 um 10:11 hat Stefan Hajnoczi geschrieben:
> On Wed, Apr 04, 2018 at 06:16:12PM +0200, Max Reitz wrote:
> > On 2018-04-04 17:01, Stefan Hajnoczi wrote:
> >  === Start mirror job and exit qemu ===
> > 
> > This seems to be independent of whether there is actually data on
> > TEST_IMG (the commit source), so something doesn't seem quite right with
> > the block job throttling here...?
> 
> I've been playing around with this test failure.  Let's leave it broken
> (!) in QEMU 2.12 because this test has uncovered a block job ratelimit
> issue that's not a regression.  The fix shouldn't be rushed.

Makes sense.

Thanks, applied to the block branch.

Kevin

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Re: [Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[Max Reitz]

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On 2018-04-10 10:11, Stefan Hajnoczi wrote:
> On Wed, Apr 04, 2018 at 06:16:12PM +0200, Max Reitz wrote:
>> On 2018-04-04 17:01, Stefan Hajnoczi wrote:
>>  === Start mirror job and exit qemu ===
>>
>> This seems to be independent of whether there is actually data on
>> TEST_IMG (the commit source), so something doesn't seem quite right with
>> the block job throttling here...?
> 
> I've been playing around with this test failure.  Let's leave it broken
> (!) in QEMU 2.12 because this test has uncovered a block job ratelimit
> issue that's not a regression.  The fix shouldn't be rushed.

OK for me.

> block/mirror.c calculates delay_ns but then discards it:
> 
>   static void coroutine_fn mirror_run(void *opaque)
>   {
>       ...
> 
>       for (;;) {
>           ...delay_ns is calculated based on job speed...
> 
>           ret = 0;
>           trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
>           if (block_job_is_cancelled(&s->common) && s->common.force) {
>               break;
>           } else if (!should_complete) {
>               delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
> 	        ^--- we discard it!
>               block_job_sleep_ns(&s->common, delay_ns);
>           }
>           s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
>       }
> 
>       ...
>   }

Uh, nice.

> This is why the mirror-based tests are completing even though we'd
> expect them to only reach the "next" iteration due to the job speed.
> 
> Increasing the 4 MB write operation in the test to >16 MB (the mirror
> buffer size) doesn't solve the problem because the next QMP command will
> race with the job's 0 ns sleep.  It would just make the test unreliable.
> 
> I'll work on the following for QEMU 2.13:
> 
> 1. Avoid spurious block_job_enter() from block_job_drain().  This
>    eliminates the extra block job iteration that changed the output in
>    the first place.
> 
> 2. Honor the job speed in block/mirror.c.
> 
> The end result will be that the test output will not require changes.

Thanks!

Max


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Re: [Qemu-devel] [PATCH for-2.12 v2] qemu-iotests: update 185 output

[QingFeng Hao]

在 2018/4/4 23:01, Stefan Hajnoczi 写道:
> Commit 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce
> vm_shutdown()") added a bdrv_drain_all() call.  As a side-effect of the
> drain operation the block job iterates one more time than before.  The
> 185 output no longer matches and the test is failing now.
> 
> It may be possible to avoid the superfluous block job iteration, but
> that type of patch is not suitable late in the QEMU 2.12 release cycle.
> 
> This patch simply updates the 185 output file.  The new behavior is
> correct, just not optimal, so make the test pass again.
> 
> Fixes: 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 ("vl: introduce vm_shutdown()")
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: QingFeng Hao <haoqf@linux.vnet.ibm.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  tests/qemu-iotests/185     | 10 ++++++----
>  tests/qemu-iotests/185.out | 12 +++++++-----
>  2 files changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/tests/qemu-iotests/185 b/tests/qemu-iotests/185
> index f5b47e4c1a..298d88d04e 100755
> --- a/tests/qemu-iotests/185
> +++ b/tests/qemu-iotests/185
> @@ -92,9 +92,8 @@ echo === Start commit job and exit qemu ===
>  echo
> 
>  # Note that the reference output intentionally includes the 'offset' field in
> -# BLOCK_JOB_CANCELLED events for all of the following block jobs. They are
> -# predictable and any change in the offsets would hint at a bug in the job
> -# throttling code.
> +# BLOCK_JOB_* events for all of the following block jobs. They are predictable
> +# and any change in the offsets would hint at a bug in the job throttling code.
>  #
>  # In order to achieve these predictable offsets, all of the following tests
>  # use speed=65536. Each job will perform exactly one iteration before it has
> @@ -102,11 +101,14 @@ echo
>  # command to be received (after receiving the command, the rest runs
>  # synchronously, so jobs can arbitrarily continue or complete).
>  #
> +# Jobs present while QEMU is terminating iterate once more due to
> +# bdrv_drain_all().
> +#
>  # The buffer size for commit and streaming is 512k (waiting for 8 seconds after
>  # the first request), for active commit and mirror it's large enough to cover
>  # the full 4M, and for backup it's the qcow2 cluster size, which we know is
>  # 64k. As all of these are at least as large as the speed, we are sure that the
> -# offset doesn't advance after the first iteration before qemu exits.
> +# offset advances exactly twice before qemu exits.
> 
>  _send_qemu_cmd $h \
>      "{ 'execute': 'block-commit',
Reviewed-by: QingFeng Hao <haoqf@linux.vnet.ibm.com>

> diff --git a/tests/qemu-iotests/185.out b/tests/qemu-iotests/185.out
> index 57eaf8d699..2c4b04de73 100644

[...]
> 

-- 
Regards
QingFeng Hao