From 0ba4c0836f702bb3abbd173c7ee486a8247331ae Mon Sep 17 00:00:00 2001

From: Hanna Reitz <hreitz@redhat.com>

Date: Tue, 18 Jan 2022 18:00:00 +0100

Subject: [PATCH 7/7] iotests/block-status-cache: New test

RH-Author: Hanna Reitz <hreitz@redhat.com>

RH-MergeRequest: 112: block/io: Update BSC only if want_zero is true

RH-Commit: [2/2] ba86b4db32c33e17a85f476d445ef0523cf8f60e

RH-Bugzilla: 2041480

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

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

Add a new test to verify that want_zero=false block-status calls do not

pollute the block-status cache for want_zero=true calls.

We check want_zero=true calls and their results using `qemu-img map`

(over NBD), and want_zero=false calls also using `qemu-img map` over

NBD, but using the qemu:allocation-depth context.

(This test case cannot be integrated into nbd-qemu-allocation, because

that is a qcow2 test, and this is a raw test.)

Signed-off-by: Hanna Reitz <hreitz@redhat.com>

Message-Id: <20220118170000.49423-3-hreitz@redhat.com>

Reviewed-by: Nir Soffer <nsoffer@redhat.com>

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

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

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

(cherry picked from commit 6384dd534d742123d26c008d9794b20bc41359d5)

Signed-off-by: Hanna Reitz <hreitz@redhat.com>

---

 tests/qemu-iotests/tests/block-status-cache   | 139 ++++++++++++++++++

 .../qemu-iotests/tests/block-status-cache.out |   5 +

 2 files changed, 144 insertions(+)

 create mode 100755 tests/qemu-iotests/tests/block-status-cache

 create mode 100644 tests/qemu-iotests/tests/block-status-cache.out

diff --git a/tests/qemu-iotests/tests/block-status-cache b/tests/qemu-iotests/tests/block-status-cache

new file mode 100755

index 0000000000..6fa10bb8f8

--- /dev/null

+++ b/tests/qemu-iotests/tests/block-status-cache

@@ -0,0 +1,139 @@

+#!/usr/bin/env python3

+# group: rw quick

+#

+# Test cases for the block-status cache.

+#

+# Copyright (C) 2022 Red Hat, Inc.

+#

+# This program is free software; you can redistribute it and/or modify

+# it under the terms of the GNU General Public License as published by

+# the Free Software Foundation; either version 2 of the License, or

+# (at your option) any later version.

+#

+# This program is distributed in the hope that it will be useful,

+# but WITHOUT ANY WARRANTY; without even the implied warranty of

+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+# GNU General Public License for more details.

+#

+# You should have received a copy of the GNU General Public License

+# along with this program.  If not, see <http://www.gnu.org/licenses/>.

+#

+

+import os

+import signal

+import iotests

+from iotests import qemu_img_create, qemu_img_pipe, qemu_nbd

+

+

+image_size = 1 * 1024 * 1024

+test_img = os.path.join(iotests.test_dir, 'test.img')

+

+nbd_pidfile = os.path.join(iotests.test_dir, 'nbd.pid')

+nbd_sock = os.path.join(iotests.sock_dir, 'nbd.sock')

+

+

+class TestBscWithNbd(iotests.QMPTestCase):

+    def setUp(self) -> None:

+        """Just create an empty image with a read-only NBD server on it"""

+        assert qemu_img_create('-f', iotests.imgfmt, test_img,

+                               str(image_size)) == 0

+

+        # Pass --allocation-depth to enable the qemu:allocation-depth context,

+        # which we are going to query to provoke a block-status inquiry with

+        # want_zero=false.

+        assert qemu_nbd(f'--socket={nbd_sock}',

+                        f'--format={iotests.imgfmt}',

+                        '--persistent',

+                        '--allocation-depth',

+                        '--read-only',

+                        f'--pid-file={nbd_pidfile}',

+                        test_img) \

+            == 0

+

+    def tearDown(self) -> None:

+        with open(nbd_pidfile, encoding='utf-8') as f:

+            pid = int(f.read())

+        os.kill(pid, signal.SIGTERM)

+        os.remove(nbd_pidfile)

+        os.remove(test_img)

+

+    def test_with_zero_bug(self) -> None:

+        """

+        Verify that the block-status cache is not corrupted by a

+        want_zero=false call.

+        We can provoke a want_zero=false call with `qemu-img map` over NBD with

+        x-dirty-bitmap=qemu:allocation-depth, so we first run a normal `map`

+        (which results in want_zero=true), then using said

+        qemu:allocation-depth context, and finally another normal `map` to

+        verify that the cache has not been corrupted.

+        """

+

+        nbd_img_opts = f'driver=nbd,server.type=unix,server.path={nbd_sock}'

+        nbd_img_opts_alloc_depth = nbd_img_opts + \

+            ',x-dirty-bitmap=qemu:allocation-depth'

+

+        # Normal map, results in want_zero=true.

+        # This will probably detect an allocated data sector first (qemu likes

+        # to allocate the first sector to facilitate alignment probing), and

+        # then the rest to be zero.  The BSC will thus contain (if anything)

+        # one range covering the first sector.

+        map_pre = qemu_img_pipe('map', '--output=json', '--image-opts',

+                                nbd_img_opts)

+

+        # qemu:allocation-depth maps for want_zero=false.

+        # want_zero=false should (with the file driver, which the server is

+        # using) report everything as data.  While this is sufficient for

+        # want_zero=false, this is nothing that should end up in the

+        # block-status cache.

+        # Due to a bug, this information did end up in the cache, though, and

+        # this would lead to wrong information being returned on subsequent

+        # want_zero=true calls.

+        #

+        # We need to run this map twice: On the first call, we probably still

+        # have the first sector in the cache, and so this will be served from

+        # the cache; and only the subsequent range will be queried from the

+        # block driver.  This subsequent range will then be entered into the

+        # cache.

+        # If we did a want_zero=true call at this point, we would thus get

+        # correct information: The first sector is not covered by the cache, so

+        # we would get fresh block-status information from the driver, which

+        # would return a data range, and this would then go into the cache,

+        # evicting the wrong range from the want_zero=false call before.

+        #

+        # Therefore, we need a second want_zero=false map to reproduce:

+        # Since the first sector is not in the cache, the query for its status

+        # will go to the driver, which will return a result that reports the

+        # whole image to be a single data area.  This result will then go into

+        # the cache, and so the cache will then report the whole image to

+        # contain data.

+        #

+        # Note that once the cache reports the whole image to contain data, any

+        # subsequent map operation will be served from the cache, and so we can

+        # never loop too many times here.

+        for _ in range(2):

+            # (Ignore the result, this is just to contaminate the cache)

+            qemu_img_pipe('map', '--output=json', '--image-opts',

+                          nbd_img_opts_alloc_depth)

+

+        # Now let's see whether the cache reports everything as data, or

+        # whether we get correct information (i.e. the same as we got on our

+        # first attempt).

+        map_post = qemu_img_pipe('map', '--output=json', '--image-opts',

+                                 nbd_img_opts)

+

+        if map_pre != map_post:

+            print('ERROR: Map information differs before and after querying ' +

+                  'qemu:allocation-depth')

+            print('Before:')

+            print(map_pre)

+            print('After:')

+            print(map_post)

+

+            self.fail("Map information differs")

+

+

+if __name__ == '__main__':

+    # The block-status cache only works on the protocol layer, so to test it,

+    # we can only use the raw format

+    iotests.main(supported_fmts=['raw'],

+                 supported_protocols=['file'])

diff --git a/tests/qemu-iotests/tests/block-status-cache.out b/tests/qemu-iotests/tests/block-status-cache.out

new file mode 100644

index 0000000000..ae1213e6f8

--- /dev/null

+++ b/tests/qemu-iotests/tests/block-status-cache.out

@@ -0,0 +1,5 @@

+.

+----------------------------------------------------------------------

+Ran 1 tests

+

+OK

-- 

2.27.0