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From 0ba4c0836f702bb3abbd173c7ee486a8247331ae Mon Sep 17 00:00:00 2001
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From: Hanna Reitz <hreitz@redhat.com>
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Date: Tue, 18 Jan 2022 18:00:00 +0100
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Subject: [PATCH 7/7] iotests/block-status-cache: New test
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RH-Author: Hanna Reitz <hreitz@redhat.com>
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RH-MergeRequest: 112: block/io: Update BSC only if want_zero is true
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RH-Commit: [2/2] ba86b4db32c33e17a85f476d445ef0523cf8f60e
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RH-Bugzilla: 2041480
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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Add a new test to verify that want_zero=false block-status calls do not
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pollute the block-status cache for want_zero=true calls.
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We check want_zero=true calls and their results using `qemu-img map`
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(over NBD), and want_zero=false calls also using `qemu-img map` over
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NBD, but using the qemu:allocation-depth context.
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(This test case cannot be integrated into nbd-qemu-allocation, because
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that is a qcow2 test, and this is a raw test.)
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Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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Message-Id: <20220118170000.49423-3-hreitz@redhat.com>
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Reviewed-by: Nir Soffer <nsoffer@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Tested-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 6384dd534d742123d26c008d9794b20bc41359d5)
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Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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---
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 tests/qemu-iotests/tests/block-status-cache   | 139 ++++++++++++++++++
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 .../qemu-iotests/tests/block-status-cache.out |   5 +
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 2 files changed, 144 insertions(+)
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 create mode 100755 tests/qemu-iotests/tests/block-status-cache
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 create mode 100644 tests/qemu-iotests/tests/block-status-cache.out
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diff --git a/tests/qemu-iotests/tests/block-status-cache b/tests/qemu-iotests/tests/block-status-cache
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new file mode 100755
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index 0000000000..6fa10bb8f8
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--- /dev/null
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+++ b/tests/qemu-iotests/tests/block-status-cache
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@@ -0,0 +1,139 @@
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+#!/usr/bin/env python3
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+# group: rw quick
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+#
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+# Test cases for the block-status cache.
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+#
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+# Copyright (C) 2022 Red Hat, Inc.
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+#
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+# This program is free software; you can redistribute it and/or modify
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+# it under the terms of the GNU General Public License as published by
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+# the Free Software Foundation; either version 2 of the License, or
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+# (at your option) any later version.
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+#
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+# This program is distributed in the hope that it will be useful,
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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+# GNU General Public License for more details.
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+#
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+# You should have received a copy of the GNU General Public License
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+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
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+#
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+
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+import os
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+import signal
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+import iotests
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+from iotests import qemu_img_create, qemu_img_pipe, qemu_nbd
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+
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+
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+image_size = 1 * 1024 * 1024
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+test_img = os.path.join(iotests.test_dir, 'test.img')
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+
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+nbd_pidfile = os.path.join(iotests.test_dir, 'nbd.pid')
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+nbd_sock = os.path.join(iotests.sock_dir, 'nbd.sock')
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+
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+
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+class TestBscWithNbd(iotests.QMPTestCase):
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+    def setUp(self) -> None:
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+        """Just create an empty image with a read-only NBD server on it"""
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+        assert qemu_img_create('-f', iotests.imgfmt, test_img,
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+                               str(image_size)) == 0
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+
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+        # Pass --allocation-depth to enable the qemu:allocation-depth context,
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+        # which we are going to query to provoke a block-status inquiry with
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+        # want_zero=false.
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+        assert qemu_nbd(f'--socket={nbd_sock}',
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+                        f'--format={iotests.imgfmt}',
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+                        '--persistent',
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+                        '--allocation-depth',
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+                        '--read-only',
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+                        f'--pid-file={nbd_pidfile}',
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+                        test_img) \
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+            == 0
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+
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+    def tearDown(self) -> None:
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+        with open(nbd_pidfile, encoding='utf-8') as f:
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+            pid = int(f.read())
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+        os.kill(pid, signal.SIGTERM)
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+        os.remove(nbd_pidfile)
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+        os.remove(test_img)
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+
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+    def test_with_zero_bug(self) -> None:
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+        """
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+        Verify that the block-status cache is not corrupted by a
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+        want_zero=false call.
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+        We can provoke a want_zero=false call with `qemu-img map` over NBD with
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+        x-dirty-bitmap=qemu:allocation-depth, so we first run a normal `map`
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+        (which results in want_zero=true), then using said
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+        qemu:allocation-depth context, and finally another normal `map` to
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+        verify that the cache has not been corrupted.
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+        """
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+
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+        nbd_img_opts = f'driver=nbd,server.type=unix,server.path={nbd_sock}'
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+        nbd_img_opts_alloc_depth = nbd_img_opts + \
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+            ',x-dirty-bitmap=qemu:allocation-depth'
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+
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+        # Normal map, results in want_zero=true.
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+        # This will probably detect an allocated data sector first (qemu likes
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+        # to allocate the first sector to facilitate alignment probing), and
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+        # then the rest to be zero.  The BSC will thus contain (if anything)
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+        # one range covering the first sector.
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+        map_pre = qemu_img_pipe('map', '--output=json', '--image-opts',
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+                                nbd_img_opts)
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+
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+        # qemu:allocation-depth maps for want_zero=false.
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+        # want_zero=false should (with the file driver, which the server is
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+        # using) report everything as data.  While this is sufficient for
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+        # want_zero=false, this is nothing that should end up in the
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+        # block-status cache.
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+        # Due to a bug, this information did end up in the cache, though, and
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+        # this would lead to wrong information being returned on subsequent
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+        # want_zero=true calls.
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+        #
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+        # We need to run this map twice: On the first call, we probably still
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+        # have the first sector in the cache, and so this will be served from
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+        # the cache; and only the subsequent range will be queried from the
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+        # block driver.  This subsequent range will then be entered into the
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+        # cache.
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+        # If we did a want_zero=true call at this point, we would thus get
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+        # correct information: The first sector is not covered by the cache, so
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+        # we would get fresh block-status information from the driver, which
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+        # would return a data range, and this would then go into the cache,
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+        # evicting the wrong range from the want_zero=false call before.
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+        #
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+        # Therefore, we need a second want_zero=false map to reproduce:
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+        # Since the first sector is not in the cache, the query for its status
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+        # will go to the driver, which will return a result that reports the
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+        # whole image to be a single data area.  This result will then go into
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+        # the cache, and so the cache will then report the whole image to
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+        # contain data.
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+        #
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+        # Note that once the cache reports the whole image to contain data, any
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+        # subsequent map operation will be served from the cache, and so we can
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+        # never loop too many times here.
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+        for _ in range(2):
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+            # (Ignore the result, this is just to contaminate the cache)
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+            qemu_img_pipe('map', '--output=json', '--image-opts',
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+                          nbd_img_opts_alloc_depth)
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+
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+        # Now let's see whether the cache reports everything as data, or
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+        # whether we get correct information (i.e. the same as we got on our
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+        # first attempt).
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+        map_post = qemu_img_pipe('map', '--output=json', '--image-opts',
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+                                 nbd_img_opts)
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+
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+        if map_pre != map_post:
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+            print('ERROR: Map information differs before and after querying ' +
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+                  'qemu:allocation-depth')
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+            print('Before:')
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+            print(map_pre)
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+            print('After:')
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+            print(map_post)
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+
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+            self.fail("Map information differs")
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+
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+
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+if __name__ == '__main__':
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+    # The block-status cache only works on the protocol layer, so to test it,
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+    # we can only use the raw format
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+    iotests.main(supported_fmts=['raw'],
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+                 supported_protocols=['file'])
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diff --git a/tests/qemu-iotests/tests/block-status-cache.out b/tests/qemu-iotests/tests/block-status-cache.out
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new file mode 100644
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index 0000000000..ae1213e6f8
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--- /dev/null
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+++ b/tests/qemu-iotests/tests/block-status-cache.out
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@@ -0,0 +1,5 @@
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+.
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+----------------------------------------------------------------------
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+Ran 1 tests
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+
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+OK
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-- 
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2.27.0
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