Merge tag 'pull-nbd-2021-12-22-v2' of https://src.openvz.org/scm/~vsementsov/qemu into staging

nbd: reconnect-on-open feature
  v2: simple fix for mypy and pylint complains on patch 04

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# gpg: Good signature from "Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>" [unknown]
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* tag 'pull-nbd-2021-12-22-v2' of https://src.openvz.org/scm/~vsementsov/qemu:
  iotests: add nbd-reconnect-on-open test
  iotests.py: add qemu_io_popen()
  iotests.py: add and use qemu_io_wrap_args()
  iotests.py: add qemu_tool_popen()
  nbd/client-connection: improve error message of cancelled attempt
  nbd/client-connection: nbd_co_establish_connection(): return real error
  nbd: allow reconnect on open, with corresponding new options

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

3 files changed, 106 insertions, 13 deletions

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 83bfedb902..1e2f2391d1 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -138,14 +138,22 @@ def unarchive_sample_image(sample, fname):
         shutil.copyfileobj(f_in, f_out)
 
 
+def qemu_tool_popen(args: Sequence[str],
+                    connect_stderr: bool = True) -> 'subprocess.Popen[str]':
+    stderr = subprocess.STDOUT if connect_stderr else None
+    # pylint: disable=consider-using-with
+    return subprocess.Popen(args,
+                            stdout=subprocess.PIPE,
+                            stderr=stderr,
+                            universal_newlines=True)
+
+
 def qemu_tool_pipe_and_status(tool: str, args: Sequence[str],
                               connect_stderr: bool = True) -> Tuple[str, int]:
     """
     Run a tool and return both its output and its exit code
     """
-    stderr = subprocess.STDOUT if connect_stderr else None
-    with subprocess.Popen(args, stdout=subprocess.PIPE,
-                          stderr=stderr, universal_newlines=True) as subp:
+    with qemu_tool_popen(args, connect_stderr) as subp:
         output = subp.communicate()[0]
         if subp.returncode < 0:
             cmd = ' '.join(args)
@@ -233,10 +241,18 @@ def img_info_log(filename, filter_path=None, imgopts=False, extra_args=()):
         filter_path = filename
     log(filter_img_info(output, filter_path))
 
+def qemu_io_wrap_args(args: Sequence[str]) -> List[str]:
+    if '-f' in args or '--image-opts' in args:
+        return qemu_io_args_no_fmt + list(args)
+    else:
+        return qemu_io_args + list(args)
+
+def qemu_io_popen(*args):
+    return qemu_tool_popen(qemu_io_wrap_args(args))
+
 def qemu_io(*args):
     '''Run qemu-io and return the stdout data'''
-    args = qemu_io_args + list(args)
-    return qemu_tool_pipe_and_status('qemu-io', args)[0]
+    return qemu_tool_pipe_and_status('qemu-io', qemu_io_wrap_args(args))[0]
 
 def qemu_io_log(*args):
     result = qemu_io(*args)
@@ -245,12 +261,7 @@ def qemu_io_log(*args):
 
 def qemu_io_silent(*args):
     '''Run qemu-io and return the exit code, suppressing stdout'''
-    if '-f' in args or '--image-opts' in args:
-        default_args = qemu_io_args_no_fmt
-    else:
-        default_args = qemu_io_args
-
-    args = default_args + list(args)
+    args = qemu_io_wrap_args(args)
     result = subprocess.run(args, stdout=subprocess.DEVNULL, check=False)
     if result.returncode < 0:
         sys.stderr.write('qemu-io received signal %i: %s\n' %
@@ -259,14 +270,14 @@ def qemu_io_silent(*args):
 
 def qemu_io_silent_check(*args):
     '''Run qemu-io and return the true if subprocess returned 0'''
-    args = qemu_io_args + list(args)
+    args = qemu_io_wrap_args(args)
     result = subprocess.run(args, stdout=subprocess.DEVNULL,
                             stderr=subprocess.STDOUT, check=False)
     return result.returncode == 0
 
 class QemuIoInteractive:
     def __init__(self, *args):
-        self.args = qemu_io_args_no_fmt + list(args)
+        self.args = qemu_io_wrap_args(args)
         # We need to keep the Popen objext around, and not
         # close it immediately. Therefore, disable the pylint check:
         # pylint: disable=consider-using-with
diff --git a/tests/qemu-iotests/tests/nbd-reconnect-on-open b/tests/qemu-iotests/tests/nbd-reconnect-on-open
new file mode 100755
index 0000000000..8be721a24f
--- /dev/null
+++ b/tests/qemu-iotests/tests/nbd-reconnect-on-open
@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+#
+# Test nbd reconnect on open
+#
+# Copyright (c) 2020 Virtuozzo International GmbH
+#
+# 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 time
+
+import iotests
+from iotests import qemu_img_create, file_path, qemu_io_popen, qemu_nbd, \
+    qemu_io_log, log
+
+iotests.script_initialize(supported_fmts=['qcow2'])
+
+disk, nbd_sock = file_path('disk', 'nbd-sock')
+
+
+def create_args(open_timeout):
+    return ['--image-opts', '-c', 'read 0 1M',
+            f'driver=nbd,open-timeout={open_timeout},'
+            f'server.type=unix,server.path={nbd_sock}']
+
+
+def check_fail_to_connect(open_timeout):
+    log(f'Check fail to connect with {open_timeout} seconds of timeout')
+
+    start_t = time.time()
+    qemu_io_log(*create_args(open_timeout))
+    delta_t = time.time() - start_t
+
+    max_delta = open_timeout + 0.2
+    if open_timeout <= delta_t <= max_delta:
+        log(f'qemu_io finished in {open_timeout}..{max_delta} seconds, OK')
+    else:
+        note = 'too early' if delta_t < open_timeout else 'too long'
+        log(f'qemu_io finished in {delta_t:.1f} seconds, {note}')
+
+
+qemu_img_create('-f', iotests.imgfmt, disk, '1M')
+
+# Start NBD client when NBD server is not yet running. It should not fail, but
+# wait for 5 seconds for the server to be available.
+client = qemu_io_popen(*create_args(5))
+
+time.sleep(1)
+qemu_nbd('-k', nbd_sock, '-f', iotests.imgfmt, disk)
+
+# client should succeed
+log(client.communicate()[0], filters=[iotests.filter_qemu_io])
+
+# Server was started without --persistent flag, so it should be off now. Let's
+# check it and at the same time check that with open-timeout=0 client fails
+# immediately.
+check_fail_to_connect(0)
+
+# Check that we will fail after non-zero timeout if server is still unavailable
+check_fail_to_connect(1)
diff --git a/tests/qemu-iotests/tests/nbd-reconnect-on-open.out b/tests/qemu-iotests/tests/nbd-reconnect-on-open.out
new file mode 100644
index 0000000000..a35ae30ea4
--- /dev/null
+++ b/tests/qemu-iotests/tests/nbd-reconnect-on-open.out
@@ -0,0 +1,11 @@
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Check fail to connect with 0 seconds of timeout
+qemu-io: can't open: Failed to connect to 'TEST_DIR/PID-nbd-sock': No such file or directory
+
+qemu_io finished in 0..0.2 seconds, OK
+Check fail to connect with 1 seconds of timeout
+qemu-io: can't open: Failed to connect to 'TEST_DIR/PID-nbd-sock': No such file or directory
+
+qemu_io finished in 1..1.2 seconds, OK