4f42bcba8f
- kvm-qemu-nbd-Pass-max-connections-to-blockdev-layer.patch [bz#1708300] - kvm-nbd-server-Allow-MULTI_CONN-for-shared-writable-expo.patch [bz#1708300] - Resolves: bz#1708300 (RFE: qemu-nbd vs NBD_FLAG_CAN_MULTI_CONN)
382 lines
14 KiB
Diff
382 lines
14 KiB
Diff
From 4a9ddf42788d3f924bdad7746f7aca615f03d7c1 Mon Sep 17 00:00:00 2001
|
|
From: Eric Blake <eblake@redhat.com>
|
|
Date: Wed, 11 May 2022 19:49:24 -0500
|
|
Subject: [PATCH 2/2] nbd/server: Allow MULTI_CONN for shared writable exports
|
|
MIME-Version: 1.0
|
|
Content-Type: text/plain; charset=UTF-8
|
|
Content-Transfer-Encoding: 8bit
|
|
|
|
RH-Author: Eric Blake <eblake@redhat.com>
|
|
RH-MergeRequest: 90: Advertise MULTI_CONN on writeable NBD servers
|
|
RH-Commit: [2/2] 53f0e885a5ed7f6e4bb14e74fe8e7957e6afe90f (ebblake/centos-qemu-kvm)
|
|
RH-Bugzilla: 1708300
|
|
RH-Acked-by: Nir Soffer <nsoffer@redhat.com>
|
|
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
|
|
RH-Acked-by: Daniel P. Berrangé <berrange@redhat.com>
|
|
|
|
According to the NBD spec, a server that advertises
|
|
NBD_FLAG_CAN_MULTI_CONN promises that multiple client connections will
|
|
not see any cache inconsistencies: when properly separated by a single
|
|
flush, actions performed by one client will be visible to another
|
|
client, regardless of which client did the flush.
|
|
|
|
We always satisfy these conditions in qemu - even when we support
|
|
multiple clients, ALL clients go through a single point of reference
|
|
into the block layer, with no local caching. The effect of one client
|
|
is instantly visible to the next client. Even if our backend were a
|
|
network device, we argue that any multi-path caching effects that
|
|
would cause inconsistencies in back-to-back actions not seeing the
|
|
effect of previous actions would be a bug in that backend, and not the
|
|
fault of caching in qemu. As such, it is safe to unconditionally
|
|
advertise CAN_MULTI_CONN for any qemu NBD server situation that
|
|
supports parallel clients.
|
|
|
|
Note, however, that we don't want to advertise CAN_MULTI_CONN when we
|
|
know that a second client cannot connect (for historical reasons,
|
|
qemu-nbd defaults to a single connection while nbd-server-add and QMP
|
|
commands default to unlimited connections; but we already have
|
|
existing means to let either style of NBD server creation alter those
|
|
defaults). This is visible by no longer advertising MULTI_CONN for
|
|
'qemu-nbd -r' without -e, as in the iotest nbd-qemu-allocation.
|
|
|
|
The harder part of this patch is setting up an iotest to demonstrate
|
|
behavior of multiple NBD clients to a single server. It might be
|
|
possible with parallel qemu-io processes, but I found it easier to do
|
|
in python with the help of libnbd, and help from Nir and Vladimir in
|
|
writing the test.
|
|
|
|
Signed-off-by: Eric Blake <eblake@redhat.com>
|
|
Suggested-by: Nir Soffer <nsoffer@redhat.com>
|
|
Suggested-by: Vladimir Sementsov-Ogievskiy <v.sementsov-og@mail.ru>
|
|
Message-Id: <20220512004924.417153-3-eblake@redhat.com>
|
|
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
|
|
|
|
(cherry picked from commit 58a6fdcc9efb2a7c1ef4893dca4aa5e8020ca3dc)
|
|
Conflicts:
|
|
nbd/server.c - context, e5fb29d5 not backported
|
|
Signed-off-by: Eric Blake <eblake@redhat.com>
|
|
---
|
|
MAINTAINERS | 1 +
|
|
blockdev-nbd.c | 5 +
|
|
docs/interop/nbd.txt | 1 +
|
|
docs/tools/qemu-nbd.rst | 3 +-
|
|
include/block/nbd.h | 3 +-
|
|
nbd/server.c | 10 +-
|
|
qapi/block-export.json | 8 +-
|
|
tests/qemu-iotests/tests/nbd-multiconn | 145 ++++++++++++++++++
|
|
tests/qemu-iotests/tests/nbd-multiconn.out | 5 +
|
|
.../tests/nbd-qemu-allocation.out | 2 +-
|
|
10 files changed, 172 insertions(+), 11 deletions(-)
|
|
create mode 100755 tests/qemu-iotests/tests/nbd-multiconn
|
|
create mode 100644 tests/qemu-iotests/tests/nbd-multiconn.out
|
|
|
|
diff --git a/MAINTAINERS b/MAINTAINERS
|
|
index 4ad2451e03..2fe20a49ab 100644
|
|
--- a/MAINTAINERS
|
|
+++ b/MAINTAINERS
|
|
@@ -3370,6 +3370,7 @@ F: qemu-nbd.*
|
|
F: blockdev-nbd.c
|
|
F: docs/interop/nbd.txt
|
|
F: docs/tools/qemu-nbd.rst
|
|
+F: tests/qemu-iotests/tests/*nbd*
|
|
T: git https://repo.or.cz/qemu/ericb.git nbd
|
|
T: git https://src.openvz.org/scm/~vsementsov/qemu.git nbd
|
|
|
|
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
|
|
index add41a23af..c6d9b0324c 100644
|
|
--- a/blockdev-nbd.c
|
|
+++ b/blockdev-nbd.c
|
|
@@ -44,6 +44,11 @@ bool nbd_server_is_running(void)
|
|
return nbd_server || qemu_nbd_connections >= 0;
|
|
}
|
|
|
|
+int nbd_server_max_connections(void)
|
|
+{
|
|
+ return nbd_server ? nbd_server->max_connections : qemu_nbd_connections;
|
|
+}
|
|
+
|
|
static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
|
|
{
|
|
nbd_client_put(client);
|
|
diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
|
|
index bdb0f2a41a..f5ca25174a 100644
|
|
--- a/docs/interop/nbd.txt
|
|
+++ b/docs/interop/nbd.txt
|
|
@@ -68,3 +68,4 @@ NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE
|
|
* 4.2: NBD_FLAG_CAN_MULTI_CONN for shareable read-only exports,
|
|
NBD_CMD_FLAG_FAST_ZERO
|
|
* 5.2: NBD_CMD_BLOCK_STATUS for "qemu:allocation-depth"
|
|
+* 7.1: NBD_FLAG_CAN_MULTI_CONN for shareable writable exports
|
|
diff --git a/docs/tools/qemu-nbd.rst b/docs/tools/qemu-nbd.rst
|
|
index 4c950f6199..8e08a29e89 100644
|
|
--- a/docs/tools/qemu-nbd.rst
|
|
+++ b/docs/tools/qemu-nbd.rst
|
|
@@ -139,8 +139,7 @@ driver options if :option:`--image-opts` is specified.
|
|
.. option:: -e, --shared=NUM
|
|
|
|
Allow up to *NUM* clients to share the device (default
|
|
- ``1``), 0 for unlimited. Safe for readers, but for now,
|
|
- consistency is not guaranteed between multiple writers.
|
|
+ ``1``), 0 for unlimited.
|
|
|
|
.. option:: -t, --persistent
|
|
|
|
diff --git a/include/block/nbd.h b/include/block/nbd.h
|
|
index c5a29ce1c6..c74b7a9d2e 100644
|
|
--- a/include/block/nbd.h
|
|
+++ b/include/block/nbd.h
|
|
@@ -1,5 +1,5 @@
|
|
/*
|
|
- * Copyright (C) 2016-2020 Red Hat, Inc.
|
|
+ * Copyright (C) 2016-2022 Red Hat, Inc.
|
|
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
|
|
*
|
|
* Network Block Device
|
|
@@ -346,6 +346,7 @@ void nbd_client_put(NBDClient *client);
|
|
|
|
void nbd_server_is_qemu_nbd(int max_connections);
|
|
bool nbd_server_is_running(void);
|
|
+int nbd_server_max_connections(void);
|
|
void nbd_server_start(SocketAddress *addr, const char *tls_creds,
|
|
const char *tls_authz, uint32_t max_connections,
|
|
Error **errp);
|
|
diff --git a/nbd/server.c b/nbd/server.c
|
|
index c5644fd3f6..6e2157acfa 100644
|
|
--- a/nbd/server.c
|
|
+++ b/nbd/server.c
|
|
@@ -1,5 +1,5 @@
|
|
/*
|
|
- * Copyright (C) 2016-2021 Red Hat, Inc.
|
|
+ * Copyright (C) 2016-2022 Red Hat, Inc.
|
|
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
|
|
*
|
|
* Network Block Device Server Side
|
|
@@ -1642,7 +1642,6 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
|
|
int64_t size;
|
|
uint64_t perm, shared_perm;
|
|
bool readonly = !exp_args->writable;
|
|
- bool shared = !exp_args->writable;
|
|
strList *bitmaps;
|
|
size_t i;
|
|
int ret;
|
|
@@ -1693,11 +1692,12 @@ static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
|
|
exp->description = g_strdup(arg->description);
|
|
exp->nbdflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_FLUSH |
|
|
NBD_FLAG_SEND_FUA | NBD_FLAG_SEND_CACHE);
|
|
+
|
|
+ if (nbd_server_max_connections() != 1) {
|
|
+ exp->nbdflags |= NBD_FLAG_CAN_MULTI_CONN;
|
|
+ }
|
|
if (readonly) {
|
|
exp->nbdflags |= NBD_FLAG_READ_ONLY;
|
|
- if (shared) {
|
|
- exp->nbdflags |= NBD_FLAG_CAN_MULTI_CONN;
|
|
- }
|
|
} else {
|
|
exp->nbdflags |= (NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_WRITE_ZEROES |
|
|
NBD_FLAG_SEND_FAST_ZERO);
|
|
diff --git a/qapi/block-export.json b/qapi/block-export.json
|
|
index 1e34927f85..755ccc89b1 100644
|
|
--- a/qapi/block-export.json
|
|
+++ b/qapi/block-export.json
|
|
@@ -21,7 +21,9 @@
|
|
# recreated on the fly while the NBD server is active.
|
|
# If missing, it will default to denying access (since 4.0).
|
|
# @max-connections: The maximum number of connections to allow at the same
|
|
-# time, 0 for unlimited. (since 5.2; default: 0)
|
|
+# time, 0 for unlimited. Setting this to 1 also stops
|
|
+# the server from advertising multiple client support
|
|
+# (since 5.2; default: 0)
|
|
#
|
|
# Since: 4.2
|
|
##
|
|
@@ -50,7 +52,9 @@
|
|
# recreated on the fly while the NBD server is active.
|
|
# If missing, it will default to denying access (since 4.0).
|
|
# @max-connections: The maximum number of connections to allow at the same
|
|
-# time, 0 for unlimited. (since 5.2; default: 0)
|
|
+# time, 0 for unlimited. Setting this to 1 also stops
|
|
+# the server from advertising multiple client support
|
|
+# (since 5.2; default: 0).
|
|
#
|
|
# Returns: error if the server is already running.
|
|
#
|
|
diff --git a/tests/qemu-iotests/tests/nbd-multiconn b/tests/qemu-iotests/tests/nbd-multiconn
|
|
new file mode 100755
|
|
index 0000000000..b121f2e363
|
|
--- /dev/null
|
|
+++ b/tests/qemu-iotests/tests/nbd-multiconn
|
|
@@ -0,0 +1,145 @@
|
|
+#!/usr/bin/env python3
|
|
+# group: rw auto quick
|
|
+#
|
|
+# Test cases for NBD multi-conn advertisement
|
|
+#
|
|
+# 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
|
|
+from contextlib import contextmanager
|
|
+import iotests
|
|
+from iotests import qemu_img_create, qemu_io
|
|
+
|
|
+
|
|
+disk = os.path.join(iotests.test_dir, 'disk')
|
|
+size = '4M'
|
|
+nbd_sock = os.path.join(iotests.sock_dir, 'nbd_sock')
|
|
+nbd_uri = 'nbd+unix:///{}?socket=' + nbd_sock
|
|
+
|
|
+
|
|
+@contextmanager
|
|
+def open_nbd(export_name):
|
|
+ h = nbd.NBD()
|
|
+ try:
|
|
+ h.connect_uri(nbd_uri.format(export_name))
|
|
+ yield h
|
|
+ finally:
|
|
+ h.shutdown()
|
|
+
|
|
+class TestNbdMulticonn(iotests.QMPTestCase):
|
|
+ def setUp(self):
|
|
+ qemu_img_create('-f', iotests.imgfmt, disk, size)
|
|
+ qemu_io('-c', 'w -P 1 0 2M', '-c', 'w -P 2 2M 2M', disk)
|
|
+
|
|
+ self.vm = iotests.VM()
|
|
+ self.vm.launch()
|
|
+ result = self.vm.qmp('blockdev-add', {
|
|
+ 'driver': 'qcow2',
|
|
+ 'node-name': 'n',
|
|
+ 'file': {'driver': 'file', 'filename': disk}
|
|
+ })
|
|
+ self.assert_qmp(result, 'return', {})
|
|
+
|
|
+ def tearDown(self):
|
|
+ self.vm.shutdown()
|
|
+ os.remove(disk)
|
|
+ try:
|
|
+ os.remove(nbd_sock)
|
|
+ except OSError:
|
|
+ pass
|
|
+
|
|
+ @contextmanager
|
|
+ def run_server(self, max_connections=None):
|
|
+ args = {
|
|
+ 'addr': {
|
|
+ 'type': 'unix',
|
|
+ 'data': {'path': nbd_sock}
|
|
+ }
|
|
+ }
|
|
+ if max_connections is not None:
|
|
+ args['max-connections'] = max_connections
|
|
+
|
|
+ result = self.vm.qmp('nbd-server-start', args)
|
|
+ self.assert_qmp(result, 'return', {})
|
|
+ yield
|
|
+
|
|
+ result = self.vm.qmp('nbd-server-stop')
|
|
+ self.assert_qmp(result, 'return', {})
|
|
+
|
|
+ def add_export(self, name, writable=None):
|
|
+ args = {
|
|
+ 'type': 'nbd',
|
|
+ 'id': name,
|
|
+ 'node-name': 'n',
|
|
+ 'name': name,
|
|
+ }
|
|
+ if writable is not None:
|
|
+ args['writable'] = writable
|
|
+
|
|
+ result = self.vm.qmp('block-export-add', args)
|
|
+ self.assert_qmp(result, 'return', {})
|
|
+
|
|
+ def test_default_settings(self):
|
|
+ with self.run_server():
|
|
+ self.add_export('r')
|
|
+ self.add_export('w', writable=True)
|
|
+ with open_nbd('r') as h:
|
|
+ self.assertTrue(h.can_multi_conn())
|
|
+ with open_nbd('w') as h:
|
|
+ self.assertTrue(h.can_multi_conn())
|
|
+
|
|
+ def test_limited_connections(self):
|
|
+ with self.run_server(max_connections=1):
|
|
+ self.add_export('r')
|
|
+ self.add_export('w', writable=True)
|
|
+ with open_nbd('r') as h:
|
|
+ self.assertFalse(h.can_multi_conn())
|
|
+ with open_nbd('w') as h:
|
|
+ self.assertFalse(h.can_multi_conn())
|
|
+
|
|
+ def test_parallel_writes(self):
|
|
+ with self.run_server():
|
|
+ self.add_export('w', writable=True)
|
|
+
|
|
+ clients = [nbd.NBD() for _ in range(3)]
|
|
+ for c in clients:
|
|
+ c.connect_uri(nbd_uri.format('w'))
|
|
+ self.assertTrue(c.can_multi_conn())
|
|
+
|
|
+ initial_data = clients[0].pread(1024 * 1024, 0)
|
|
+ self.assertEqual(initial_data, b'\x01' * 1024 * 1024)
|
|
+
|
|
+ updated_data = b'\x03' * 1024 * 1024
|
|
+ clients[1].pwrite(updated_data, 0)
|
|
+ clients[2].flush()
|
|
+ current_data = clients[0].pread(1024 * 1024, 0)
|
|
+
|
|
+ self.assertEqual(updated_data, current_data)
|
|
+
|
|
+ for i in range(3):
|
|
+ clients[i].shutdown()
|
|
+
|
|
+
|
|
+if __name__ == '__main__':
|
|
+ try:
|
|
+ # Easier to use libnbd than to try and set up parallel
|
|
+ # 'qemu-nbd --list' or 'qemu-io' processes, but not all systems
|
|
+ # have libnbd installed.
|
|
+ import nbd # type: ignore
|
|
+
|
|
+ iotests.main(supported_fmts=['qcow2'])
|
|
+ except ImportError:
|
|
+ iotests.notrun('libnbd not installed')
|
|
diff --git a/tests/qemu-iotests/tests/nbd-multiconn.out b/tests/qemu-iotests/tests/nbd-multiconn.out
|
|
new file mode 100644
|
|
index 0000000000..8d7e996700
|
|
--- /dev/null
|
|
+++ b/tests/qemu-iotests/tests/nbd-multiconn.out
|
|
@@ -0,0 +1,5 @@
|
|
+...
|
|
+----------------------------------------------------------------------
|
|
+Ran 3 tests
|
|
+
|
|
+OK
|
|
diff --git a/tests/qemu-iotests/tests/nbd-qemu-allocation.out b/tests/qemu-iotests/tests/nbd-qemu-allocation.out
|
|
index 0bf1abb063..9d938db24e 100644
|
|
--- a/tests/qemu-iotests/tests/nbd-qemu-allocation.out
|
|
+++ b/tests/qemu-iotests/tests/nbd-qemu-allocation.out
|
|
@@ -17,7 +17,7 @@ wrote 2097152/2097152 bytes at offset 1048576
|
|
exports available: 1
|
|
export: ''
|
|
size: 4194304
|
|
- flags: 0x58f ( readonly flush fua df multi cache )
|
|
+ flags: 0x48f ( readonly flush fua df cache )
|
|
min block: 1
|
|
opt block: 4096
|
|
max block: 33554432
|
|
--
|
|
2.31.1
|
|
|