[PATCH v2 0/3] iotests: fix three spurious local failures

[PATCH v2 0/3] iotests: fix three spurious local failures

[Denis V. Lunev]

Three independent fixes found while chasing a clean './check -qcow2'
run on a Python 3.14 host. Unrelated to each other, sent as one
series since they came out of the same session.

v2:
- patch 1: drop the now-unused 'Pool' import (Kevin)
- patch 2: rename _notrun_on_no_fuse to _notrun_on_fuse_error (Kevin)
- patch 3: replace the dropped assertion with a check that bitmap0's
  content on the destination has not reached its final value right
  after RESUME, throttling migration bandwidth

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

Denis V. Lunev (3):
  iotests: run the test pool with the 'fork' start method
  iotests: skip FUSE tests when FUSE is not usable
  iotests/migrate-bitmaps-postcopy-test: replace the timing assertion
    with a content check

 tests/qemu-iotests/common.rc                      | 14 ++++++++++++++
 tests/qemu-iotests/testrunner.py                  |  4 ++--
 tests/qemu-iotests/tests/file-io-error            |  4 +---
 tests/qemu-iotests/tests/fuse-allow-other         |  2 ++
 tests/qemu-iotests/tests/fuse-mmap-shared         |  9 ++++++---
 .../tests/migrate-bitmaps-postcopy-test           | 15 ++++++++++++++-
 6 files changed, 39 insertions(+), 9 deletions(-)

-- 
2.53.0

[PATCH v2 1/3] iotests: run the test pool with the 'fork' start method

[Denis V. Lunev]

run_tests_pool() shares the runner via the class attribute
TestRunner.shared_self, relying on worker processes to inherit it.
That only works with the 'fork' start method. Python 3.14 switched
the Linux default to 'forkserver', so workers see shared_self as
None and parallel runs abort with:

  assert runner is not None
  AssertionError

Only reproduces with Python 3.14+ and 'check -jN' (N > 1); meson
runs one test per process and never calls run_tests_pool(), so CI
is unaffected.

Request get_context('fork') explicitly; it is available on all
supported Python versions and a no-op before 3.14.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
---
 tests/qemu-iotests/testrunner.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/qemu-iotests/testrunner.py b/tests/qemu-iotests/testrunner.py
index dbe2dddc32..cc36867719 100644
--- a/tests/qemu-iotests/testrunner.py
+++ b/tests/qemu-iotests/testrunner.py
@@ -26,7 +26,7 @@
 import json
 import shutil
 import sys
-from multiprocessing import Pool
+from multiprocessing import get_context
 from typing import List, Optional, Any, Sequence, Dict
 from testenv import TestEnv
 
@@ -125,7 +125,7 @@ def run_tests_pool(self, tests: List[str],
         assert TestRunner.shared_self is None
         TestRunner.shared_self = self
 
-        with Pool(jobs) as p:
+        with get_context('fork').Pool(jobs) as p:
             results = p.starmap(self.proc_run_test,
                                 zip(tests, [test_field_width] * len(tests)))
 
-- 
2.53.0

Re: [PATCH v2 1/3] iotests: run the test pool with the 'fork' start method

[Daniel P. Berrangé]

On Wed, Jul 15, 2026 at 12:34:49PM +0200, Denis V. Lunev wrote:
> run_tests_pool() shares the runner via the class attribute
> TestRunner.shared_self, relying on worker processes to inherit it.
> That only works with the 'fork' start method. Python 3.14 switched
> the Linux default to 'forkserver', so workers see shared_self as
> None and parallel runs abort with:
> 
>   assert runner is not None
>   AssertionError
> 
> Only reproduces with Python 3.14+ and 'check -jN' (N > 1); meson
> runs one test per process and never calls run_tests_pool(), so CI
> is unaffected.
> 
> Request get_context('fork') explicitly; it is available on all
> supported Python versions and a no-op before 3.14.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> ---
>  tests/qemu-iotests/testrunner.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
-- 
|: https://berrange.com       ~~        https://hachyderm.io/@berrange :|
|: https://libvirt.org          ~~          https://entangle-photo.org :|
|: https://pixelfed.art/berrange   ~~    https://fstop138.berrange.com :|

[PATCH v2 2/3] iotests: skip FUSE tests when FUSE is not usable

[Denis V. Lunev]

file-io-error, fuse-allow-other and fuse-mmap-shared skip only when
FUSE is not compiled in. When FUSE is built in but unusable at run
time (no /dev/fuse access, fusermount lacking permissions), the
export fails to mount with "Failed to mount FUSE session to export"
and the tests report a spurious failure instead of skipping, like
NBD tests already do for missing NBD support.

Add _notrun_on_fuse_error() to common.rc and use it in the shell
tests. fuse-mmap-shared is Python, so it gets an equivalent inline
check.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
---
 tests/qemu-iotests/common.rc              | 14 ++++++++++++++
 tests/qemu-iotests/tests/file-io-error    |  4 +---
 tests/qemu-iotests/tests/fuse-allow-other |  2 ++
 tests/qemu-iotests/tests/fuse-mmap-shared |  9 ++++++---
 4 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index 298bc483e0..bcb1ec50a9 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -981,6 +981,20 @@ _require_drivers()
     done
 }
 
+# Skip if FUSE is unusable: not compiled in, or the export failed to
+# mount. $1 is the failing 'block-export-add' reply.
+_notrun_on_fuse_error()
+{
+    case "$1" in
+        *"Parameter 'type' does not accept value 'fuse'"*)
+            _notrun "No FUSE support"
+            ;;
+        *"Failed to mount FUSE session"*)
+            _notrun "FUSE not usable in this environment"
+            ;;
+    esac
+}
+
 # Check that we have a file system that allows huge (but very sparse) files
 #
 _require_large_file()
diff --git a/tests/qemu-iotests/tests/file-io-error b/tests/qemu-iotests/tests/file-io-error
index fb8db73b31..0d970c102f 100755
--- a/tests/qemu-iotests/tests/file-io-error
+++ b/tests/qemu-iotests/tests/file-io-error
@@ -89,9 +89,7 @@ output=$(_send_qemu_cmd $QEMU_HANDLE \
     'return' \
     | grep -v 'option allow_other only allowed if')
 
-if echo "$output" | grep -q "Parameter 'type' does not accept value 'fuse'"; then
-    _notrun 'No FUSE support'
-fi
+_notrun_on_fuse_error "$output"
 echo "$output"
 
 echo
diff --git a/tests/qemu-iotests/tests/fuse-allow-other b/tests/qemu-iotests/tests/fuse-allow-other
index eaa39f8f23..50a36601d7 100755
--- a/tests/qemu-iotests/tests/fuse-allow-other
+++ b/tests/qemu-iotests/tests/fuse-allow-other
@@ -77,6 +77,8 @@ fuse_export_add()
         _notrun "allow_other not supported"
     fi
 
+    _notrun_on_fuse_error "$output"
+
     echo "$output"
 }
 
diff --git a/tests/qemu-iotests/tests/fuse-mmap-shared b/tests/qemu-iotests/tests/fuse-mmap-shared
index 52941a3bb6..b190105894 100755
--- a/tests/qemu-iotests/tests/fuse-mmap-shared
+++ b/tests/qemu-iotests/tests/fuse-mmap-shared
@@ -28,9 +28,12 @@ def test_fuse_support(mount_point):
     })
     test_qsd.stop()
     if 'error' in res:
-        assert (res['error']['desc'] ==
-                "Parameter 'type' does not accept value 'fuse'")
-        iotests.notrun('No FUSE support')
+        desc = res['error']['desc']
+        if desc == "Parameter 'type' does not accept value 'fuse'":
+            iotests.notrun('No FUSE support')
+        if 'Failed to mount FUSE session' in desc:
+            iotests.notrun('FUSE not usable in this environment')
+        assert False, desc
 
 # Shared mmap when using direct IO is only supported for Linux kernels >= 6.6
 # with commit e78662e818f94 ("fuse: add a new fuse init flag to relax
-- 
2.53.0

Re: [PATCH v2 2/3] iotests: skip FUSE tests when FUSE is not usable

[Daniel P. Berrangé]

On Wed, Jul 15, 2026 at 12:34:50PM +0200, Denis V. Lunev wrote:
> file-io-error, fuse-allow-other and fuse-mmap-shared skip only when
> FUSE is not compiled in. When FUSE is built in but unusable at run
> time (no /dev/fuse access, fusermount lacking permissions), the
> export fails to mount with "Failed to mount FUSE session to export"
> and the tests report a spurious failure instead of skipping, like
> NBD tests already do for missing NBD support.
> 
> Add _notrun_on_fuse_error() to common.rc and use it in the shell
> tests. fuse-mmap-shared is Python, so it gets an equivalent inline
> check.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> ---
>  tests/qemu-iotests/common.rc              | 14 ++++++++++++++
>  tests/qemu-iotests/tests/file-io-error    |  4 +---
>  tests/qemu-iotests/tests/fuse-allow-other |  2 ++
>  tests/qemu-iotests/tests/fuse-mmap-shared |  9 ++++++---
>  4 files changed, 23 insertions(+), 6 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
-- 
|: https://berrange.com       ~~        https://hachyderm.io/@berrange :|
|: https://libvirt.org          ~~          https://entangle-photo.org :|
|: https://pixelfed.art/berrange   ~~    https://fstop138.berrange.com :|

[PATCH v2 3/3] iotests/migrate-bitmaps-postcopy-test: replace the timing assertion with a content check

[Denis V. Lunev]

`downtime * 10 < postcopy_time` was an unnormalized wall-clock
heuristic (commit e80a4150a5) that fails on fast hosts, where the
bitmap payload now transfers in under a second.

Check the actual invariant instead: right after RESUME, bitmap0's
content hash on the destination must not yet match the fully
migrated value. Throttle max-bandwidth first, since all-zero chunks
skip the payload write and would otherwise let a fast host finish
the transfer before the check runs.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
---
 .../tests/migrate-bitmaps-postcopy-test           | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tests/qemu-iotests/tests/migrate-bitmaps-postcopy-test b/tests/qemu-iotests/tests/migrate-bitmaps-postcopy-test
index c519e6db8c..33ff2b861f 100755
--- a/tests/qemu-iotests/tests/migrate-bitmaps-postcopy-test
+++ b/tests/qemu-iotests/tests/migrate-bitmaps-postcopy-test
@@ -160,12 +160,26 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
 
         self.vm_b.cmd('migrate-set-capabilities', capabilities=caps)
 
+        # Throttle so the chunks covering our discards (the only ones
+        # not skipped by the all-zero fast path) can't outrun the check
+        # below.
+        self.vm_a.cmd('migrate-set-parameters', max_bandwidth=16536)
+
         self.vm_a.cmd('migrate', uri='exec:cat>' + fifo)
 
         self.vm_a.cmd('migrate-start-postcopy')
 
         event_resume = self.vm_b.event_wait('RESUME')
         self.vm_b_events.append(event_resume)
+
+        # bitmap0 can't already have its final content: that requires
+        # the bit data to have actually arrived.
+        result = self.vm_b.qmp('x-debug-block-dirty-bitmap-sha256',
+                               node='drive0', name='bitmap0')
+        assert result['return']['sha256'] != all_discards_sha256
+
+        self.vm_a.cmd('migrate-set-parameters', max_bandwidth=0)
+
         return (event_resume, discards1_sha256, all_discards_sha256)
 
     def test_postcopy_success(self):
@@ -186,7 +200,6 @@ class TestDirtyBitmapPostcopyMigration(iotests.QMPTestCase):
         downtime = event_dist(event_stop, event_resume)
         postcopy_time = event_dist(event_resume, event_complete)
 
-        assert downtime * 10 < postcopy_time
         if debug:
             print('downtime:', downtime)
             print('postcopy_time:', postcopy_time)
-- 
2.53.0

Re: [PATCH v2 3/3] iotests/migrate-bitmaps-postcopy-test: replace the timing assertion with a content check

[Vladimir Sementsov-Ogievskiy]

On 15.07.26 13:34, Denis V. Lunev wrote:
> `downtime * 10 < postcopy_time` was an unnormalized wall-clock
> heuristic (commit e80a4150a5) that fails on fast hosts, where the
> bitmap payload now transfers in under a second.
> 
> Check the actual invariant instead: right after RESUME, bitmap0's
> content hash on the destination must not yet match the fully
> migrated value. Throttle max-bandwidth first, since all-zero chunks
> skip the payload write and would otherwise let a fast host finish
> the transfer before the check runs.
> 
> Signed-off-by: Denis V. Lunev<den@openvz.org>
> CC: Kevin Wolf<kwolf@redhat.com>
> CC: Hanna Reitz<hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy<vsementsov@yandex-team.ru>

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

-- 
Best regards,
Vladimir

Re: [PATCH v2 0/3] iotests: fix three spurious local failures

[Denis V. Lunev]

On 7/15/26 12:34, Denis V. Lunev wrote:
> This email originated from an IP that might not be authorized by the domain it was sent from.
> Do not click links or open attachments unless it is an email you expected to receive.
> Three independent fixes found while chasing a clean './check -qcow2'
> run on a Python 3.14 host. Unrelated to each other, sent as one
> series since they came out of the same session.
>
> v2:
> - patch 1: drop the now-unused 'Pool' import (Kevin)
> - patch 2: rename _notrun_on_no_fuse to _notrun_on_fuse_error (Kevin)
> - patch 3: replace the dropped assertion with a check that bitmap0's
>   content on the destination has not reached its final value right
>   after RESUME, throttling migration bandwidth
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
>
> Denis V. Lunev (3):
>   iotests: run the test pool with the 'fork' start method
>   iotests: skip FUSE tests when FUSE is not usable
>   iotests/migrate-bitmaps-postcopy-test: replace the timing assertion
>     with a content check
>
>  tests/qemu-iotests/common.rc                      | 14 ++++++++++++++
>  tests/qemu-iotests/testrunner.py                  |  4 ++--
>  tests/qemu-iotests/tests/file-io-error            |  4 +---
>  tests/qemu-iotests/tests/fuse-allow-other         |  2 ++
>  tests/qemu-iotests/tests/fuse-mmap-shared         |  9 ++++++---
>  .../tests/migrate-bitmaps-postcopy-test           | 15 ++++++++++++++-
>  6 files changed, 39 insertions(+), 9 deletions(-)
>
ping