[PATCH 0/3] nbd reconnect on open

[PATCH 0/3] nbd reconnect on open

[Vladimir Sementsov-Ogievskiy]

Hi all! There is a new feature: reconnect on open. It is useful when
start of vm and start of nbd server are not simple to sync.

This is based on "[PATCH 0/4] nbd reconnect new fixes"
Based-on: <20200903190301.367620-1-vsementsov@virtuozzo.com>

Vladimir Sementsov-Ogievskiy (3):
  block/nbd: move initial connect to coroutine
  nbd: allow reconnect on open, with corresponding new options
  iotests: add 306 to test reconnect on nbd open

 block/nbd.c                   | 173 +++++++++++++++++++++++++---------
 tests/qemu-iotests/306        |  46 +++++++++
 tests/qemu-iotests/306.out    |   5 +
 tests/qemu-iotests/group      |   1 +
 tests/qemu-iotests/iotests.py |  11 +++
 5 files changed, 190 insertions(+), 46 deletions(-)
 create mode 100755 tests/qemu-iotests/306
 create mode 100644 tests/qemu-iotests/306.out

-- 
2.21.3

[PATCH 1/3] block/nbd: move initial connect to coroutine

[Vladimir Sementsov-Ogievskiy]

We are going to implement reconnect-on-open. Let's reuse existing
reconnect loop. For this, do initial connect in connection coroutine.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/nbd.c | 94 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 53 insertions(+), 41 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 4548046cd7..16f039b7dc 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -57,6 +57,7 @@ typedef struct {
 } NBDClientRequest;
 
 typedef enum NBDClientState {
+    NBD_CLIENT_OPENING,
     NBD_CLIENT_CONNECTING_WAIT,
     NBD_CLIENT_CONNECTING_NOWAIT,
     NBD_CLIENT_CONNECTED,
@@ -113,6 +114,7 @@ typedef struct BDRVNBDState {
     CoQueue free_sema;
     Coroutine *connection_co;
     Coroutine *teardown_co;
+    Coroutine *open_co;
     QemuCoSleepState *connection_co_sleep_ns_state;
     bool drained;
     bool wait_drained_end;
@@ -140,8 +142,6 @@ typedef struct BDRVNBDState {
     NBDConnectThread *connect_thread;
 } BDRVNBDState;
 
-static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
-                                                  Error **errp);
 static QIOChannelSocket *nbd_co_establish_connection(BlockDriverState *bs,
                                                      Error **errp);
 static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
@@ -338,7 +338,8 @@ static void nbd_teardown_connection(BlockDriverState *bs)
 static bool nbd_client_connecting(BDRVNBDState *s)
 {
     return s->state == NBD_CLIENT_CONNECTING_WAIT ||
-        s->state == NBD_CLIENT_CONNECTING_NOWAIT;
+        s->state == NBD_CLIENT_CONNECTING_NOWAIT ||
+        s->state == NBD_CLIENT_OPENING;
 }
 
 static bool nbd_client_connecting_wait(BDRVNBDState *s)
@@ -638,6 +639,7 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
 {
     uint64_t timeout = 1 * NANOSECONDS_PER_SECOND;
     uint64_t max_timeout = 16 * NANOSECONDS_PER_SECOND;
+    bool initial_connect = s->state == NBD_CLIENT_OPENING;
 
     if (s->state == NBD_CLIENT_CONNECTING_WAIT) {
         reconnect_delay_timer_init(s, qemu_clock_get_ns(QEMU_CLOCK_REALTIME) +
@@ -646,6 +648,25 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
 
     nbd_reconnect_attempt(s);
 
+    if (initial_connect) {
+        if (s->state == NBD_CLIENT_CONNECTED) {
+            /* All good. Just kick nbd_open() to successfully return */
+            if (s->open_co) {
+                aio_co_wake(s->open_co);
+                s->open_co = NULL;
+            }
+            aio_wait_kick();
+            return;
+        } else {
+            /*
+             * Failed. Currently, reconnect on open is not allowed, so quit.
+             * nbd_open() will be kicked in the end of nbd_connection_entry()
+             */
+            s->state = NBD_CLIENT_QUIT;
+            return;
+        }
+    }
+
     while (nbd_client_connecting(s)) {
         if (s->drained) {
             bdrv_dec_in_flight(s->bs);
@@ -758,6 +779,11 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
         s->ioc = NULL;
     }
 
+    if (s->open_co) {
+        aio_co_wake(s->open_co);
+        s->open_co = NULL;
+    }
+
     if (s->teardown_co) {
         aio_co_wake(s->teardown_co);
     }
@@ -1746,26 +1772,6 @@ static void nbd_client_close(BlockDriverState *bs)
     nbd_teardown_connection(bs);
 }
 
-static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
-                                                  Error **errp)
-{
-    ERRP_GUARD();
-    QIOChannelSocket *sioc;
-
-    sioc = qio_channel_socket_new();
-    qio_channel_set_name(QIO_CHANNEL(sioc), "nbd-client");
-
-    qio_channel_socket_connect_sync(sioc, saddr, errp);
-    if (*errp) {
-        object_unref(OBJECT(sioc));
-        return NULL;
-    }
-
-    qio_channel_set_delay(QIO_CHANNEL(sioc), false);
-
-    return sioc;
-}
-
 /* nbd_client_handshake takes ownership on sioc. On failure it is unref'ed. */
 static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
                                 Error **errp)
@@ -2229,7 +2235,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
 {
     int ret;
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
-    QIOChannelSocket *sioc;
 
     ret = nbd_process_options(bs, options, errp);
     if (ret < 0) {
@@ -2239,23 +2244,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     s->bs = bs;
     qemu_co_mutex_init(&s->send_mutex);
     qemu_co_queue_init(&s->free_sema);
-
-    /*
-     * establish TCP connection, return error if it fails
-     * TODO: Configurable retry-until-timeout behaviour.
-     */
-    sioc = nbd_establish_connection(s->saddr, errp);
-    if (!sioc) {
-        return -ECONNREFUSED;
-    }
-
-    ret = nbd_client_handshake(bs, sioc, errp);
-    if (ret < 0) {
-        nbd_clear_bdrvstate(s);
-        return ret;
-    }
-    /* successfully connected */
-    s->state = NBD_CLIENT_CONNECTED;
+    s->state = NBD_CLIENT_OPENING;
 
     nbd_init_connect_thread(s);
 
@@ -2263,6 +2252,29 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     bdrv_inc_in_flight(bs);
     aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);
 
+    if (qemu_in_coroutine()) {
+        s->open_co = qemu_coroutine_self();
+        qemu_coroutine_yield();
+    } else {
+        BDRV_POLL_WHILE(bs, s->state == NBD_CLIENT_OPENING);
+    }
+
+    if (s->state != NBD_CLIENT_CONNECTED && s->connect_status < 0) {
+        /*
+         * It's possible that state != NBD_CLIENT_CONNECTED, but connect_status
+         * is 0. This means that initial connecting succeed, but failed later
+         * (during BDRV_POLL_WHILE). It's a rare case, but it happen in iotest
+         * 83. Let's don't care and just report success in this case: it not
+         * much differs from the case when connection failed immediately after
+         * succeeded open.
+         */
+        assert(s->connect_err);
+        error_propagate(errp, s->connect_err);
+        s->connect_err = NULL;
+        nbd_clear_bdrvstate(s);
+        return s->connect_status;
+    }
+
     return 0;
 }
 
-- 
2.21.3

[PATCH 2/3] nbd: allow reconnect on open, with corresponding new options

[Vladimir Sementsov-Ogievskiy]

Note: currently, using new option with long timeout in qmp command
blockdev-add is not good idea, as qmp interface is blocking, so,
don't add it now, let's add it later after
"monitor: Optionally run handlers in coroutines" series merged.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/nbd.c | 115 +++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 92 insertions(+), 23 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 16f039b7dc..8fea5ededb 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -125,12 +125,14 @@ typedef struct BDRVNBDState {
     bool wait_in_flight;
 
     QEMUTimer *reconnect_delay_timer;
+    QEMUTimer *open_timer;
 
     NBDClientRequest requests[MAX_NBD_REQUESTS];
     NBDReply reply;
     BlockDriverState *bs;
 
     /* Connection parameters */
+    uint64_t open_timeout;
     uint32_t reconnect_delay;
     SocketAddress *saddr;
     char *export, *tlscredsid;
@@ -304,7 +306,7 @@ static void coroutine_fn nbd_client_co_drain_end(BlockDriverState *bs)
 }
 
 
-static void nbd_teardown_connection(BlockDriverState *bs)
+static void nbd_teardown_connection_async(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
 
@@ -324,6 +326,14 @@ static void nbd_teardown_connection(BlockDriverState *bs)
         }
         nbd_co_establish_connection_cancel(bs, true);
     }
+}
+
+static void nbd_teardown_connection(BlockDriverState *bs)
+{
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+
+    nbd_teardown_connection_async(bs);
+
     if (qemu_in_coroutine()) {
         s->teardown_co = qemu_coroutine_self();
         /* connection_co resumes us when it terminates */
@@ -473,6 +483,11 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
     s->wait_connect = true;
     qemu_coroutine_yield();
 
+    if (!s->connect_thread) {
+        error_setg(errp, "Connection attempt cancelled by other operation");
+        return NULL;
+    }
+
     qemu_mutex_lock(&thr->mutex);
 
     switch (thr->state) {
@@ -528,6 +543,12 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
     bool wake = false;
     bool do_free = false;
 
+    if (!thr) {
+        /* already detached or finished */
+        assert(!s->wait_connect);
+        return;
+    }
+
     qemu_mutex_lock(&thr->mutex);
 
     if (thr->state == CONNECT_THREAD_RUNNING) {
@@ -623,10 +644,15 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
     bdrv_inc_in_flight(s->bs);
 
 out:
-    s->connect_status = ret;
-    error_free(s->connect_err);
-    s->connect_err = NULL;
-    error_propagate(&s->connect_err, local_err);
+    if (s->connect_status == -ETIMEDOUT) {
+        /* Don't rewrite timeout error by following cancel-provoked error */
+        error_free(local_err);
+    } else {
+        s->connect_status = ret;
+        error_free(s->connect_err);
+        s->connect_err = NULL;
+        error_propagate(&s->connect_err, local_err);
+    }
 
     if (ret >= 0) {
         /* successfully connected */
@@ -635,11 +661,44 @@ out:
     }
 }
 
+static void open_timer_del(BDRVNBDState *s)
+{
+    if (s->open_timer) {
+        timer_del(s->open_timer);
+        timer_free(s->open_timer);
+        s->open_timer = NULL;
+    }
+}
+
+static void open_timer_cb(void *opaque)
+{
+    BDRVNBDState *s = opaque;
+
+    if (!s->connect_status) {
+        /* First attempt was not finished. We should set an error */
+        s->connect_status = -ETIMEDOUT;
+        error_setg(&s->connect_err, "First connection attempt is cancelled by "
+                   "timeout");
+    }
+
+    nbd_teardown_connection_async(s->bs);
+    open_timer_del(s);
+}
+
+static void open_timer_init(BDRVNBDState *s, uint64_t expire_time_ns)
+{
+    assert(!s->open_timer && s->state == NBD_CLIENT_OPENING);
+    s->open_timer = aio_timer_new(bdrv_get_aio_context(s->bs),
+                                  QEMU_CLOCK_REALTIME,
+                                  SCALE_NS,
+                                  open_timer_cb, s);
+    timer_mod(s->open_timer, expire_time_ns);
+}
+
 static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
 {
     uint64_t timeout = 1 * NANOSECONDS_PER_SECOND;
     uint64_t max_timeout = 16 * NANOSECONDS_PER_SECOND;
-    bool initial_connect = s->state == NBD_CLIENT_OPENING;
 
     if (s->state == NBD_CLIENT_CONNECTING_WAIT) {
         reconnect_delay_timer_init(s, qemu_clock_get_ns(QEMU_CLOCK_REALTIME) +
@@ -648,23 +707,9 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
 
     nbd_reconnect_attempt(s);
 
-    if (initial_connect) {
-        if (s->state == NBD_CLIENT_CONNECTED) {
-            /* All good. Just kick nbd_open() to successfully return */
-            if (s->open_co) {
-                aio_co_wake(s->open_co);
-                s->open_co = NULL;
-            }
-            aio_wait_kick();
-            return;
-        } else {
-            /*
-             * Failed. Currently, reconnect on open is not allowed, so quit.
-             * nbd_open() will be kicked in the end of nbd_connection_entry()
-             */
-            s->state = NBD_CLIENT_QUIT;
-            return;
-        }
+    if (s->state == NBD_CLIENT_OPENING && !s->open_timeout) {
+        s->state = NBD_CLIENT_QUIT;
+        return;
     }
 
     while (nbd_client_connecting(s)) {
@@ -694,6 +739,16 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
     }
 
     reconnect_delay_timer_del(s);
+    open_timer_del(s);
+
+    if (s->state == NBD_CLIENT_CONNECTED) {
+        /* All good. Just kick nbd_open() to successfully return */
+        if (s->open_co) {
+            aio_co_wake(s->open_co);
+            s->open_co = NULL;
+        }
+        aio_wait_kick();
+    }
 }
 
 static coroutine_fn void nbd_connection_entry(void *opaque)
@@ -2164,6 +2219,14 @@ static QemuOptsList nbd_runtime_opts = {
                     "future requests before a successful reconnect will "
                     "immediately fail. Default 0",
         },
+        {
+            .name = "open-timeout",
+            .type = QEMU_OPT_NUMBER,
+            .help = "In seconds. If zero, nbd driver tries to establish "
+                    "connection only once, on fail open fails. If non-zero, "
+                    "nbd driver may do several attempts until success or "
+                    "@open-timeout seconds passed. Default 0",
+        },
         { /* end of list */ }
     },
 };
@@ -2219,6 +2282,7 @@ static int nbd_process_options(BlockDriverState *bs, QDict *options,
     }
 
     s->reconnect_delay = qemu_opt_get_number(opts, "reconnect-delay", 0);
+    s->open_timeout = qemu_opt_get_number(opts, "open-timeout", 0);
 
     ret = 0;
 
@@ -2252,6 +2316,11 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     bdrv_inc_in_flight(bs);
     aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);
 
+    if (s->open_timeout) {
+        open_timer_init(s, qemu_clock_get_ns(QEMU_CLOCK_REALTIME) +
+                        s->open_timeout * NANOSECONDS_PER_SECOND);
+    }
+
     if (qemu_in_coroutine()) {
         s->open_co = qemu_coroutine_self();
         qemu_coroutine_yield();
-- 
2.21.3

[PATCH 3/3] iotests: add 306 to test reconnect on nbd open

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
---
 tests/qemu-iotests/306        | 46 +++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/306.out    |  5 ++++
 tests/qemu-iotests/group      |  1 +
 tests/qemu-iotests/iotests.py | 11 +++++++++
 4 files changed, 63 insertions(+)
 create mode 100755 tests/qemu-iotests/306
 create mode 100644 tests/qemu-iotests/306.out

diff --git a/tests/qemu-iotests/306 b/tests/qemu-iotests/306
new file mode 100755
index 0000000000..4b8b4090be
--- /dev/null
+++ b/tests/qemu-iotests/306
@@ -0,0 +1,46 @@
+#!/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
+
+disk, nbd_sock = file_path('disk', 'nbd-sock')
+qemu_img_create('-f', iotests.imgfmt, disk, '1M')
+
+client = qemu_io_popen('--image-opts', '-c', 'read 0 1M',
+                       'driver=nbd,__virtuozzo_open-reconnect-attempts=4,'
+                       'server.type=unix,server.path=' + nbd_sock)
+
+time.sleep(2)
+
+qemu_nbd('-k', nbd_sock, '-f', iotests.imgfmt, disk)
+
+iotests.log(client.communicate()[0], filters=[iotests.filter_qemu_io])
+
+client = qemu_io_popen('--image-opts', '-c', 'read 0 1M',
+                       'driver=nbd,__virtuozzo_open-reconnect-attempts=1,'
+                       'server.type=unix,server.path=' + nbd_sock)
+
+time.sleep(1.5)
+
+iotests.log(client.communicate()[0], filters=[iotests.filter_qemu_io,
+                                              iotests.filter_testfiles])
diff --git a/tests/qemu-iotests/306.out b/tests/qemu-iotests/306.out
new file mode 100644
index 0000000000..82c74b4a2d
--- /dev/null
+++ b/tests/qemu-iotests/306.out
@@ -0,0 +1,5 @@
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+can't open: Failed to connect socket TEST_DIR/PID-nbd-sock: No such file or directory
+
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 5cad015231..e2b479ffb1 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -313,3 +313,4 @@
 302 quick
 303 rw quick
 304 rw quick
+306 rw auto quick
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index e197c73ca5..7d8f53fe19 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -195,6 +195,17 @@ def qemu_io_log(*args):
     log(result, filters=[filter_testfiles, filter_qemu_io])
     return result
 
+def qemu_io_popen(*args):
+    '''Run qemu-nbd in daemon mode and return the parent's exit code'''
+    default_args = qemu_io_args[:]
+
+    if ('-f' in args or '--image-opts' in args) and '-f' in default_args:
+        ind = default_args.index('-f')
+        del default_args[ind:ind+2]
+
+    return subprocess.Popen(default_args + list(args), stdout=subprocess.PIPE,
+                            stderr=subprocess.STDOUT)
+
 def qemu_io_silent(*args):
     '''Run qemu-io and return the exit code, suppressing stdout'''
     args = qemu_io_args + list(args)
-- 
2.21.3