[PATCH qemu 0/4] block/qemu-img convert: better handle failing flush

[PATCH qemu 0/4] block/qemu-img convert: better handle failing flush

[Fiona Ebner]

Flush during bdrv_close() was introduced back in 2012 in commit
80ccf93b88 ("qemu-img: let 'qemu-img convert' flush data"). However, a
failing flush was quietly ignored. Report the error instead, since
this could mean that the image contents are not as expected. See patch
3/4 for details.

With 'qemu-img convert', when using a cache mode with 'cache.no-flush
= off', the expectation is that the data is flushed to the disk, which
happens since commit 80ccf93b88 ("qemu-img: let 'qemu-img convert'
flush data"). This expectation also encompasses that failure to do so
is properly reported, so ensure that 'qemu-img convert' exits with a
non-zero status code when the target image cannot be flushed. See
patch 4/4 for details.

qemu:

Fiona Ebner (4):
  iotests: add test cases for failing flush after qemu-img convert
  iotests.py: add filter_qemu()
  block: report flush error during bdrv_close()
  qemu-img: convert: flush target image after copying

 block.c                                    | 13 +++-
 qemu-img.c                                 |  8 ++-
 tests/qemu-iotests/026                     | 10 +--
 tests/qemu-iotests/026.out                 | 84 ++++++++++++++++++++++
 tests/qemu-iotests/071                     |  2 +-
 tests/qemu-iotests/071.out                 |  2 +
 tests/qemu-iotests/080.out                 |  2 +
 tests/qemu-iotests/098.out                 |  4 ++
 tests/qemu-iotests/122                     | 33 +++++++++
 tests/qemu-iotests/122.out                 | 17 +++++
 tests/qemu-iotests/244                     |  2 +-
 tests/qemu-iotests/244.out                 |  1 +
 tests/qemu-iotests/iotests.py              |  4 ++
 tests/qemu-iotests/tests/file-io-error     |  2 +-
 tests/qemu-iotests/tests/file-io-error.out |  2 +
 tests/qemu-iotests/tests/qsd-migrate       |  5 +-
 tests/qemu-iotests/tests/qsd-migrate.out   |  1 +
 17 files changed, 180 insertions(+), 12 deletions(-)


Summary over all repositories:
  17 files changed, 180 insertions(+), 12 deletions(-)

-- 
Generated by git-murpp 0.5.0

[PATCH qemu 1/4] iotests: add test cases for failing flush after qemu-img convert

[Fiona Ebner]

In preparation to add more checks in the following commits and show
how the behavior changes.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 tests/qemu-iotests/122     | 33 +++++++++++++++++++++++++++++++++
 tests/qemu-iotests/122.out | 14 ++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/tests/qemu-iotests/122 b/tests/qemu-iotests/122
index be0f6b79e5..488649f1bd 100755
--- a/tests/qemu-iotests/122
+++ b/tests/qemu-iotests/122
@@ -334,6 +334,39 @@ echo
 $QEMU_IMG convert -O $IMGFMT -o preallocation=metadata -n \
 	  "$TEST_IMG" "$TEST_IMG".orig && echo "unexpected success"
 
+echo
+echo "=== failing flush after convert with default ('unsafe') cache mode ==="
+echo
+
+TEST_IMG="$TEST_IMG".orig _make_test_img 1M
+TEST_IMG="$TEST_IMG" _make_test_img 1M
+
+$QEMU_IO -c "write -P 42 0 1M" "$TEST_IMG".orig | _filter_qemu_io
+
+target_fails_flush="json:{
+    'driver': '$IMGFMT',
+    'file': {
+        'driver': 'blkdebug',
+        'inject-error': [{
+            'event': 'flush_to_disk'
+        }],
+        'image': {
+            'driver': 'file',
+            'filename': '$TEST_IMG'
+        }
+    }
+}"
+
+$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush"
+echo "qemu-img convert exited with status $?"
+
+echo
+echo "=== failing flush after convert with 'writeback' cache mode ==="
+echo
+
+$QEMU_IMG convert -t writeback -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush"
+echo "qemu-img convert exited with status $?"
+
 # success, all done
 echo '*** done'
 rm -f $seq.full
diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out
index 6a1aa3fe2b..f3e28f33bc 100644
--- a/tests/qemu-iotests/122.out
+++ b/tests/qemu-iotests/122.out
@@ -256,4 +256,18 @@ Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=67108864
 === -n incompatible with -o ===
 
 qemu-img: -o has no effect when skipping image creation
+
+=== failing flush after convert with default ('unsafe') cache mode ===
+
+Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=1048576
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576
+wrote 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-img convert exited with status 0
+
+=== failing flush after convert with 'writeback' cache mode ===
+
+qemu-img: Failed to flush the L2 table cache: Input/output error
+qemu-img: Failed to flush the refcount block cache: Input/output error
+qemu-img convert exited with status 0
 *** done
-- 
2.47.3

Re: [PATCH qemu 1/4] iotests: add test cases for failing flush after qemu-img convert

[Eric Blake]

On Wed, Sep 30, 2026 at 03:19:22PM +0200, Fiona Ebner wrote:
> In preparation to add more checks in the following commits and show
> how the behavior changes.
> 
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
>  tests/qemu-iotests/122     | 33 +++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/122.out | 14 ++++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/tests/qemu-iotests/122 b/tests/qemu-iotests/122
> index be0f6b79e5..488649f1bd 100755
> --- a/tests/qemu-iotests/122
> +++ b/tests/qemu-iotests/122

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

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org

[PATCH qemu 2/4] iotests.py: add filter_qemu()

[Fiona Ebner]

Add a filter_qemu() helper function for replacing the QEMU program
name with 'QEMU_PROG' in test's log messages.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 tests/qemu-iotests/iotests.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 7d5a77a85e..642a160bb2 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -596,6 +596,10 @@ def filter_qemu_io(msg):
     return qemu_io_re.sub("X ops; XX:XX:XX.X "
                           "(XXX YYY/sec and XXX ops/sec)", msg)
 
+qemu_re = re.compile(r"%s" % os.path.basename(qemu_prog))
+def filter_qemu(msg):
+    return qemu_re.sub("QEMU_PROG", msg)
+
 chown_re = re.compile(r"chown [0-9]+:[0-9]+")
 def filter_chown(msg):
     return chown_re.sub("chown UID:GID", msg)
-- 
2.47.3

Re: [PATCH qemu 2/4] iotests.py: add filter_qemu()

[Eric Blake]

On Wed, Sep 30, 2026 at 03:19:23PM +0200, Fiona Ebner wrote:
> Add a filter_qemu() helper function for replacing the QEMU program
> name with 'QEMU_PROG' in test's log messages.
> 
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
>  tests/qemu-iotests/iotests.py | 4 ++++
>  1 file changed, 4 insertions(+)

I'm surprised we didn't already have this ;)

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

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org

[PATCH qemu 3/4] block: report flush error during bdrv_close()

[Fiona Ebner]

Flush during bdrv_close() was introduced back in 2012 in commit
80ccf93b88 ("qemu-img: let 'qemu-img convert' flush data"). However, a
failing flush was quietly ignored [0]. Report the error instead, since
this could mean that the image contents are not as expected.

Adapt the iotests accordingly. For all tests except '080' and
'qsd-migrate' the failures come from blkdebug configurations. For
'080', the failures are also directly expected, because of invalid L1
table size and offset. For the 'qsd-migrate' test, the error happens,
because the QSD node which is attached via NBD to the source VM was
inactivated.

[0]: Note that the errors reported for qcow2 come from
qcow2_inactivate() which is only called as part of
bs->drv->bdrv_close() after bdrv_flush(). In particular, adding
> 'once': 'on'
to the blkdebug driver in the relevant test case in the 122 iotest
shows that the failure can be silent in case of qcow2 too.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 block.c                                    | 13 +++-
 tests/qemu-iotests/026                     | 10 +--
 tests/qemu-iotests/026.out                 | 84 ++++++++++++++++++++++
 tests/qemu-iotests/071                     |  2 +-
 tests/qemu-iotests/071.out                 |  2 +
 tests/qemu-iotests/080.out                 |  2 +
 tests/qemu-iotests/098.out                 |  4 ++
 tests/qemu-iotests/122                     |  8 +--
 tests/qemu-iotests/122.out                 |  2 +
 tests/qemu-iotests/244                     |  2 +-
 tests/qemu-iotests/244.out                 |  1 +
 tests/qemu-iotests/tests/file-io-error     |  2 +-
 tests/qemu-iotests/tests/file-io-error.out |  2 +
 tests/qemu-iotests/tests/qsd-migrate       |  5 +-
 tests/qemu-iotests/tests/qsd-migrate.out   |  1 +
 15 files changed, 125 insertions(+), 15 deletions(-)

diff --git a/block.c b/block.c
index f0a6042e61..c05ad01f25 100644
--- a/block.c
+++ b/block.c
@@ -5162,12 +5162,23 @@ static void GRAPH_UNLOCKED bdrv_close(BlockDriverState *bs)
 {
     BdrvAioNotifier *ban, *ban_next;
     BdrvChild *child, *next;
+    int ret;
 
     GLOBAL_STATE_CODE();
     assert(!bs->refcnt);
 
     bdrv_drained_begin(bs); /* complete I/O */
-    bdrv_flush(bs);
+    ret = bdrv_flush(bs);
+    if (ret < 0) {
+        const char *name;
+        if (bs->filename[0]) {
+            name = bs->filename;
+        } else {
+            name = bdrv_get_node_name(bs);
+        }
+        error_report("Failed flush for '%s' during close: %s", name,
+                     strerror(-ret));
+    }
     bdrv_drain(bs); /* in case flush left pending I/O */
 
     if (bs->drv) {
diff --git a/tests/qemu-iotests/026 b/tests/qemu-iotests/026
index d37e266dad..88cb4dd934 100755
--- a/tests/qemu-iotests/026
+++ b/tests/qemu-iotests/026
@@ -103,13 +103,13 @@ if [ "$event" == "l2_update" ]; then
     $QEMU_IO -c "write $vmstate 0 512" "$TEST_IMG" > /dev/null 2>&1
 fi
 
-$QEMU_IO -c "write $vmstate 0 128k " "$BLKDBG_TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write $vmstate 0 128k " "$BLKDBG_TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
 
 # l2_load is not called on allocation, so issue a second write
 # Reads are another path to trigger l2_load, so do a read, too
 if [ "$event" == "l2_load" ]; then
-    $QEMU_IO -c "write $vmstate 0 128k " "$BLKDBG_TEST_IMG" | _filter_qemu_io
-    $QEMU_IO -c "read $vmstate 0 128k " "$BLKDBG_TEST_IMG" | _filter_qemu_io
+    $QEMU_IO -c "write $vmstate 0 128k " "$BLKDBG_TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
+    $QEMU_IO -c "read $vmstate 0 128k " "$BLKDBG_TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
 fi
 
 _check_test_img_ignore_leaks 2>&1 | grep -v "refcount=1 reference=0"
@@ -155,7 +155,7 @@ _make_test_img 1G
 
 echo
 echo "Event: $event; errno: $errno; imm: $imm; once: $once; write $vmstate"
-$QEMU_IO -c "write $vmstate 0 64M" "$BLKDBG_TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write $vmstate 0 64M" "$BLKDBG_TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
 
 _check_test_img_ignore_leaks 2>&1 | grep -v "refcount=1 reference=0"
 
@@ -194,7 +194,7 @@ _make_test_img 1G
 
 echo
 echo "Event: $event; errno: $errno; imm: $imm; once: $once"
-$QEMU_IO -c "write -b 0 64k" "$BLKDBG_TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write -b 0 64k" "$BLKDBG_TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
 
 _check_test_img_ignore_leaks 2>&1 | grep -v "refcount=1 reference=0"
 
diff --git a/tests/qemu-iotests/026.out b/tests/qemu-iotests/026.out
index b998a9ac83..47bd88b1d3 100644
--- a/tests/qemu-iotests/026.out
+++ b/tests/qemu-iotests/026.out
@@ -15,15 +15,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_update; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_update; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -39,15 +43,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_update; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_update; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -127,15 +135,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_update; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_update; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -151,15 +163,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_update; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_update; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -175,15 +191,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_alloc_write; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_alloc_write; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -199,15 +219,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_alloc_write; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l2_alloc_write; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -223,15 +247,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: write_aio; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: write_aio; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -247,15 +275,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: write_aio; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: write_aio; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -271,15 +303,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_load; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_load; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -295,15 +331,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_load; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_load; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -319,15 +359,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_update_part; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_update_part; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -343,15 +387,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_update_part; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_update_part; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -367,15 +415,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc; errno: 5; imm: off; once: off; write
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc; errno: 5; imm: off; once: off; write -b
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -391,15 +443,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -458,15 +514,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_hookup; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_hookup; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -482,15 +542,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_write; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_write; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -506,15 +570,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_write_blocks; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_write_blocks; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -530,15 +598,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_write_table; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_write_table; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -554,15 +626,19 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_switch_table; errno: 28; imm: off; once: off; write
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: refblock_alloc_switch_table; errno: 28; imm: off; once: off; write -b
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 
 === L1 growth tests ===
@@ -596,8 +672,10 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_grow_write_table; errno: 5; imm: off; once: off
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -608,8 +686,10 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_grow_write_table; errno: 28; imm: off; once: off
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -620,8 +700,10 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_grow_activate_table; errno: 5; imm: off; once: off
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 qemu-io: Failed to flush the L2 table cache: Input/output error
 qemu-io: Failed to flush the refcount block cache: Input/output error
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: Input/output error
 No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -632,8 +714,10 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
 Event: l1_grow_activate_table; errno: 28; imm: off; once: off
 qemu-io: write failed: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 qemu-io: Failed to flush the L2 table cache: No space left on device
 qemu-io: Failed to flush the refcount block cache: No space left on device
+qemu-io: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.qcow2' during close: No space left on device
 No errors were found on the image.
 
 === Avoid cluster leaks after temporary failure ===
diff --git a/tests/qemu-iotests/071 b/tests/qemu-iotests/071
index 83c4ce6314..8237b325ea 100755
--- a/tests/qemu-iotests/071
+++ b/tests/qemu-iotests/071
@@ -54,7 +54,7 @@ do_run_qemu()
 
 run_qemu()
 {
-    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qemu | _filter_qmp | _filter_qemu_io
+    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qemu | _filter_qmp | _filter_qemu_io | _filter_json_filename
 }
 
 IMG_SIZE=64M
diff --git a/tests/qemu-iotests/071.out b/tests/qemu-iotests/071.out
index f2d015d8cc..a69e6f7e50 100644
--- a/tests/qemu-iotests/071.out
+++ b/tests/qemu-iotests/071.out
@@ -83,8 +83,10 @@ wrote 512/512 bytes at offset 0
 {"return": ""}
 {"return": "Error: read failed: Input/output error\r\n"}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+QEMU_PROG: Failed flush for 'json:{ /* filtered */ }' during close: Input/output error
 QEMU_PROG: Failed to flush the L2 table cache: Input/output error
 QEMU_PROG: Failed to flush the refcount block cache: Input/output error
+QEMU_PROG: Failed flush for 'json:{ /* filtered */ }' during close: Input/output error
 {"return": {}}
 
 *** done
diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
index b20c21faf6..3b2b27c5fe 100644
--- a/tests/qemu-iotests/080.out
+++ b/tests/qemu-iotests/080.out
@@ -67,6 +67,7 @@ qemu-img: Failed to load snapshot: Snapshot L1 table offset invalid
 qemu-img: Snapshot L1 table offset invalid
 qemu-img: Failed to turn zero into data clusters: Invalid argument
 qemu-io: write failed: Invalid argument
+qemu-io: Failed flush for 'TEST_DIR/t.qcow2' during close: Invalid argument
 qemu-io: Failed to flush the refcount block cache: Invalid argument
 qemu-img: Snapshot L1 table offset invalid
 qemu-img: Could not apply snapshot 'test': Failed to load snapshot: Invalid argument
@@ -90,6 +91,7 @@ qemu-img: Failed to load snapshot: Snapshot L1 table too large
 qemu-img: Snapshot L1 table too large
 qemu-img: Failed to turn zero into data clusters: File too large
 qemu-io: write failed: File too large
+qemu-io: Failed flush for 'TEST_DIR/t.qcow2' during close: File too large
 qemu-io: Failed to flush the refcount block cache: File too large
 qemu-img: Snapshot L1 table too large
 qemu-img: Could not apply snapshot 'test': Failed to load snapshot: File too large
diff --git a/tests/qemu-iotests/098.out b/tests/qemu-iotests/098.out
index 6c73dd0977..912b0290af 100644
--- a/tests/qemu-iotests/098.out
+++ b/tests/qemu-iotests/098.out
@@ -6,6 +6,7 @@ Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-img: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT' during close: Input/output error
 qemu-img: Failed to empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
 No errors were found on the image.
 
@@ -15,6 +16,7 @@ Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-img: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT' during close: Input/output error
 qemu-img: Failed to empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
 Leaked cluster 4 refcount=1 reference=0
 Leaked cluster 5 refcount=1 reference=0
@@ -28,6 +30,7 @@ Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-img: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT' during close: Input/output error
 qemu-img: Failed to empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
 ERROR cluster 0 refcount=0 reference=1
 ERROR cluster 1 refcount=0 reference=1
@@ -42,6 +45,7 @@ Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-img: Failed flush for 'blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT' during close: Input/output error
 qemu-img: Failed to empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
 ERROR cluster 0 refcount=0 reference=1
 ERROR cluster 1 refcount=0 reference=1
diff --git a/tests/qemu-iotests/122 b/tests/qemu-iotests/122
index 488649f1bd..9da1246f09 100755
--- a/tests/qemu-iotests/122
+++ b/tests/qemu-iotests/122
@@ -357,15 +357,15 @@ target_fails_flush="json:{
     }
 }"
 
-$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush"
-echo "qemu-img convert exited with status $?"
+$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush" 2>&1 | _filter_json_filename
+echo "qemu-img convert exited with status ${PIPESTATUS[0]}"
 
 echo
 echo "=== failing flush after convert with 'writeback' cache mode ==="
 echo
 
-$QEMU_IMG convert -t writeback -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush"
-echo "qemu-img convert exited with status $?"
+$QEMU_IMG convert -t writeback -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush" 2>&1 | _filter_json_filename
+echo "qemu-img convert exited with status ${PIPESTATUS[0]}"
 
 # success, all done
 echo '*** done'
diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out
index f3e28f33bc..84283f2434 100644
--- a/tests/qemu-iotests/122.out
+++ b/tests/qemu-iotests/122.out
@@ -267,7 +267,9 @@ qemu-img convert exited with status 0
 
 === failing flush after convert with 'writeback' cache mode ===
 
+qemu-img: Failed flush for 'json:{ /* filtered */ }' during close: Input/output error
 qemu-img: Failed to flush the L2 table cache: Input/output error
 qemu-img: Failed to flush the refcount block cache: Input/output error
+qemu-img: Failed flush for 'json:{ /* filtered */ }' during close: Input/output error
 qemu-img convert exited with status 0
 *** done
diff --git a/tests/qemu-iotests/244 b/tests/qemu-iotests/244
index 2a98ad58f5..ef32f8ec03 100755
--- a/tests/qemu-iotests/244
+++ b/tests/qemu-iotests/244
@@ -264,7 +264,7 @@ $QEMU_IO -c 'write 0 512' -c flush \
              }
          }
      }" \
-    | _filter_qemu_io
+    2>&1 | _filter_qemu_io | _filter_generated_node_ids
 
 result=${PIPESTATUS[0]}
 echo
diff --git a/tests/qemu-iotests/244.out b/tests/qemu-iotests/244.out
index c5e62146c9..81463d6f0e 100644
--- a/tests/qemu-iotests/244.out
+++ b/tests/qemu-iotests/244.out
@@ -134,6 +134,7 @@ Images are identical.
 
 === Flushing should flush the data file ===
 
+qemu-io: Failed flush for 'NODE_NAME' during close: Input/output error
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
diff --git a/tests/qemu-iotests/tests/file-io-error b/tests/qemu-iotests/tests/file-io-error
index 0d970c102f..3885b741d9 100755
--- a/tests/qemu-iotests/tests/file-io-error
+++ b/tests/qemu-iotests/tests/file-io-error
@@ -94,7 +94,7 @@ echo "$output"
 
 echo
 # This should fail, but gracefully, i.e. just print an I/O error, not crash.
-$QEMU_IO -f file -c 'write 0 64M' "$TEST_DIR/fuse-export" | _filter_qemu_io
+$QEMU_IO -f file -c 'write 0 64M' "$TEST_DIR/fuse-export" 2>&1 | _filter_qemu_io | _filter_testdir
 echo
 
 capture_events=BLOCK_EXPORT_DELETED _send_qemu_cmd $QEMU_HANDLE \
diff --git a/tests/qemu-iotests/tests/file-io-error.out b/tests/qemu-iotests/tests/file-io-error.out
index bf8c0018ba..748ea3079c 100644
--- a/tests/qemu-iotests/tests/file-io-error.out
+++ b/tests/qemu-iotests/tests/file-io-error.out
@@ -22,6 +22,7 @@ QA output created by file-io-error
 {"return": {}}
 
 qemu-io: write failed: Input/output error
+qemu-io: Failed flush for 'TEST_DIR/fuse-export' during close: Input/output error
 
 {'execute': 'block-export-del',
       'arguments': {'id': 'exp0'}}
@@ -29,5 +30,6 @@ qemu-io: write failed: Input/output error
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "exp0"}}
 {'execute': 'blockdev-del',
       'arguments': {'node-name': 'node0'}}
+QEMU_PROG: Failed flush for 'node0' during close: Input/output error
 {"return": {}}
 *** done
diff --git a/tests/qemu-iotests/tests/qsd-migrate b/tests/qemu-iotests/tests/qsd-migrate
index d76278b576..73583dec16 100755
--- a/tests/qemu-iotests/tests/qsd-migrate
+++ b/tests/qemu-iotests/tests/qsd-migrate
@@ -20,7 +20,7 @@
 
 import iotests
 
-from iotests import filter_qemu_io, filter_qtest
+from iotests import filter_qemu, filter_qemu_io, filter_qtest
 
 iotests.script_initialize(supported_fmts=['qcow2', 'qed', 'raw'],
                           supported_protocols=['file'],
@@ -126,11 +126,12 @@ with iotests.FilePath('disk.img') as path, \
 
     iotests.log('\nDone')
 
+    # NOTE: Flush during close fails here, since the QSD node was inactivated.
     vm_src.shutdown()
     iotests.log('\n--- vm_src log ---')
     log = vm_src.get_log()
     if log:
-        iotests.log(log, [filter_qtest, filter_qemu_io])
+        iotests.log(log, [filter_qtest, filter_qemu_io, filter_qemu])
     qsd_src.stop()
 
     vm_dst.shutdown()
diff --git a/tests/qemu-iotests/tests/qsd-migrate.out b/tests/qemu-iotests/tests/qsd-migrate.out
index 4a5241e5d4..894b232b4a 100644
--- a/tests/qemu-iotests/tests/qsd-migrate.out
+++ b/tests/qemu-iotests/tests/qsd-migrate.out
@@ -47,6 +47,7 @@ read 4096/4096 bytes at offset 0
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 4096/4096 bytes at offset 0
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+QEMU_PROG: Failed flush for 'disk' during close: Operation not permitted
 
 --- vm_dst log ---
 read 4096/4096 bytes at offset 0
-- 
2.47.3

Re: [PATCH qemu 3/4] block: report flush error during bdrv_close()

[Eric Blake]

On Wed, Sep 30, 2026 at 03:19:24PM +0200, Fiona Ebner wrote:
> Flush during bdrv_close() was introduced back in 2012 in commit
> 80ccf93b88 ("qemu-img: let 'qemu-img convert' flush data"). However, a
> failing flush was quietly ignored [0]. Report the error instead, since
> this could mean that the image contents are not as expected.
> 
> Adapt the iotests accordingly. For all tests except '080' and
> 'qsd-migrate' the failures come from blkdebug configurations. For
> '080', the failures are also directly expected, because of invalid L1
> table size and offset. For the 'qsd-migrate' test, the error happens,
> because the QSD node which is attached via NBD to the source VM was
> inactivated.
> 
> [0]: Note that the errors reported for qcow2 come from
> qcow2_inactivate() which is only called as part of
> bs->drv->bdrv_close() after bdrv_flush(). In particular, adding
> > 'once': 'on'
> to the blkdebug driver in the relevant test case in the 122 iotest
> shows that the failure can be silent in case of qcow2 too.
> 
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---

> +++ b/tests/qemu-iotests/026
> @@ -103,13 +103,13 @@ if [ "$event" == "l2_update" ]; then
>      $QEMU_IO -c "write $vmstate 0 512" "$TEST_IMG" > /dev/null 2>&1
>  fi
>  
> -$QEMU_IO -c "write $vmstate 0 128k " "$BLKDBG_TEST_IMG" | _filter_qemu_io
> +$QEMU_IO -c "write $vmstate 0 128k " "$BLKDBG_TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir

This creates lines longer than 80 columns. Adding \-newline
continuations is an option. But there are plenty of existing long
lines in the iotests, so I don't see that as holding up this patch.

> +++ b/tests/qemu-iotests/122
> @@ -357,15 +357,15 @@ target_fails_flush="json:{
>      }
>  }"
>  
> -$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush"
> -echo "qemu-img convert exited with status $?"
> +$QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n "$TEST_IMG".orig "$target_fails_flush" 2>&1 | _filter_json_filename
> +echo "qemu-img convert exited with status ${PIPESTATUS[0]}"

Interesting churn from $? to ${PIPESTATUS[0]} on a line added earlier
in the same series. But using PIPESTATUS when there is no |, while
valid in bash, looks odd, so I don't mind.

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

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org

[PATCH qemu 4/4] qemu-img: convert: flush target image after copying

[Fiona Ebner]

With 'qemu-img convert', when using a cache mode with 'cache.no-flush
= off', the expectation is that the data is flushed to the disk, which
happens since commit 80ccf93b88 ("qemu-img: let 'qemu-img convert'
flush data"). This expectation also encompasses that failure to do so
is properly reported, so ensure that 'qemu-img convert' exits with a
non-zero status code when the target image cannot be flushed.

In particular, the reproducer below [0], based on a report by
Ing. Alfonso Kuen Arroyo [1], would result in
> rc=0
> Content mismatch at offset XYZ!
before this change, and in
> rc=1
> Content mismatch at offset XYZ!
after this change.

Note that this change does not affect the (default) 'unsafe' cache
mode, because bdrv_co_flush() still skips flush to disk for that cache
mode.

[0]:
> #!/bin/bash -x
> dd if=/dev/urandom of=src.raw bs=1M count=500
> truncate -s 500M dst.img
> LOOP=$(losetup --find --show dst.img)
> SIZE=$(blockdev --getsz $LOOP)
> dd if=/dev/zero of=$LOOP bs=1M count=500 conv=fsync status=none
> sync
> echo 3 > /proc/sys/vm/drop_caches
> dmsetup create flk --table "0 $SIZE flakey $LOOP 0 5 5"
> qemu-img convert -t writeback -p -r 100M -f raw -O raw src.raw /dev/mapper/flk
> echo rc=$?
> sleep 5
> dmsetup remove flk
> qemu-img compare src.raw $LOOP
> losetup -d $LOOP
> rm src.raw dst.img

[1]: https://lore.proxmox.com/pve-devel/178961792132.43804.17173233935297903311@idkmanager.com/

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 qemu-img.c                 | 8 +++++++-
 tests/qemu-iotests/122.out | 3 ++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/qemu-img.c b/qemu-img.c
index 2f63d31141..edf75e43ab 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2245,7 +2245,7 @@ static int img_convert(const img_cmd_t *ccmd, int argc, char **argv)
     Error *local_err = NULL;
     bool writethrough, src_writethrough, image_opts = false,
          skip_create = false, progress = false, tgt_image_opts = false;
-    int64_t ret = -EINVAL;
+    int64_t ret = -EINVAL, ret2;
     bool force_share = false;
     bool explict_min_sparse = false;
     bool bitmaps = false;
@@ -2872,6 +2872,12 @@ static int img_convert(const img_cmd_t *ccmd, int argc, char **argv)
         ret = convert_copy_bitmaps(blk_bs(s.src[0]), out_bs, skip_broken);
     }
 
+    ret2 = blk_flush(s.target);
+    if (ret2 < 0) {
+        error_report("Failed to flush target image: %s", strerror(-ret2));
+        ret = ret != 0 ? ret : ret2;
+    }
+
 out:
     if (!ret) {
         qemu_progress_print(100, 0);
diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out
index 84283f2434..38794f96ac 100644
--- a/tests/qemu-iotests/122.out
+++ b/tests/qemu-iotests/122.out
@@ -267,9 +267,10 @@ qemu-img convert exited with status 0
 
 === failing flush after convert with 'writeback' cache mode ===
 
+qemu-img: Failed to flush target image: Input/output error
 qemu-img: Failed flush for 'json:{ /* filtered */ }' during close: Input/output error
 qemu-img: Failed to flush the L2 table cache: Input/output error
 qemu-img: Failed to flush the refcount block cache: Input/output error
 qemu-img: Failed flush for 'json:{ /* filtered */ }' during close: Input/output error
-qemu-img convert exited with status 0
+qemu-img convert exited with status 1
 *** done
-- 
2.47.3

Re: [PATCH qemu 4/4] qemu-img: convert: flush target image after copying

[Eric Blake]

On Wed, Sep 30, 2026 at 03:19:25PM +0200, Fiona Ebner wrote:
> With 'qemu-img convert', when using a cache mode with 'cache.no-flush
> = off', the expectation is that the data is flushed to the disk, which
> happens since commit 80ccf93b88 ("qemu-img: let 'qemu-img convert'
> flush data"). This expectation also encompasses that failure to do so
> is properly reported, so ensure that 'qemu-img convert' exits with a
> non-zero status code when the target image cannot be flushed.
> 
> In particular, the reproducer below [0], based on a report by
> Ing. Alfonso Kuen Arroyo [1], would result in
> > rc=0
> > Content mismatch at offset XYZ!
> before this change, and in
> > rc=1
> > Content mismatch at offset XYZ!
> after this change.
> 
> Note that this change does not affect the (default) 'unsafe' cache
> mode, because bdrv_co_flush() still skips flush to disk for that cache
> mode.

Should we rethink the default? I get that during a long-running
qemu-img convert, it makes sense to avoid intermediate calls to flush
(the destination image is not going to be in use by a guest until the
qemu-img process completes, so there is no need to slow down the
conversion). But should we have a mode of operation where we guarantee
that we flush before exiting qemu-img, while ginoring all other flush
points in the middle (in between an explicit request for all
intermediate flushes to be acted on, vs. an explicit request to not do
any flushing at all), as as safer default going forward? That way, you
have to explicitly opt in to a case where qemu-img convert might
produce a corrupted copy due to an undiagnosed flush failure.

But I think that question can be deferred to another day - this patch
has merit of adding diagnosis for the setup of anyone explicitly
requesting flush safety of some sort, even if it doesn't change
behavior for the defaults when the user did not make an explicit flush
request.

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

This series caught my eyes because of the scenario you mentioned of an
NBD connection dying before a flush can finalize; so I'm planning on
queuing it through my NBD tree shortly.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org