[PULL 00/34] NBD patches for 2021-06-15

[PULL 00/34] NBD patches for 2021-06-15

[Eric Blake]

The following changes since commit 1ea06abceec61b6f3ab33dadb0510b6e09fb61e2:

  Merge remote-tracking branch 'remotes/berrange-gitlab/tags/misc-fixes-pull-request' into staging (2021-06-14 15:59:13 +0100)

are available in the Git repository at:

  https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2021-06-15

for you to fetch changes up to 788b68b57dea4ddd0038f73b96c147eb406c386d:

  block/nbd: safer transition to receiving request (2021-06-15 15:42:33 -0500)

----------------------------------------------------------------
nbd patches for 2021-06-15

- bug fixes in coroutine aio context handling
- rework NBD client connection logic to perform more work in coroutine
rather than blocking main loop

----------------------------------------------------------------
Paolo Bonzini (2):
      async: the main AioContext is only "current" if under the BQL
      tests: cover aio_co_enter from a worker thread without BQL taken

Roman Kagan (2):
      block/nbd: fix channel object leak
      block/nbd: ensure ->connection_thread is always valid

Vladimir Sementsov-Ogievskiy (30):
      co-queue: drop extra coroutine_fn marks
      block/nbd: fix how state is cleared on nbd_open() failure paths
      block/nbd: connect_thread_func(): do qio_channel_set_delay(false)
      qemu-sockets: introduce socket_address_parse_named_fd()
      block/nbd: call socket_address_parse_named_fd() in advance
      block/nbd: nbd_client_handshake(): fix leak of s->ioc
      block/nbd: BDRVNBDState: drop unused connect_err and connect_status
      block/nbd: simplify waking of nbd_co_establish_connection()
      block/nbd: drop thr->state
      block/nbd: bs-independent interface for nbd_co_establish_connection()
      block/nbd: make nbd_co_establish_connection_cancel() bs-independent
      block/nbd: rename NBDConnectThread to NBDClientConnection
      block/nbd: introduce nbd_client_connection_new()
      block/nbd: introduce nbd_client_connection_release()
      nbd: move connection code from block/nbd to nbd/client-connection
      nbd/client-connection: use QEMU_LOCK_GUARD
      nbd/client-connection: add possibility of negotiation
      nbd/client-connection: implement connection retry
      nbd/client-connection: shutdown connection on release
      block/nbd: split nbd_handle_updated_info out of nbd_client_handshake()
      block/nbd: use negotiation of NBDClientConnection
      block/nbd: don't touch s->sioc in nbd_teardown_connection()
      block/nbd: drop BDRVNBDState::sioc
      nbd/client-connection: return only one io channel
      block-coroutine-wrapper: allow non bdrv_ prefix
      block/nbd: split nbd_co_do_establish_connection out of nbd_reconnect_attempt
      nbd/client-connection: add option for non-blocking connection attempt
      block/nbd: reuse nbd_co_do_establish_connection() in nbd_open()
      block/nbd: add nbd_client_connected() helper
      block/nbd: safer transition to receiving request

 scripts/block-coroutine-wrapper.py |   7 +-
 block/coroutines.h                 |   6 +
 include/block/aio.h                |   5 +-
 include/block/nbd.h                |  18 ++
 include/qemu/coroutine.h           |   6 +-
 include/qemu/sockets.h             |  11 +
 block/nbd.c                        | 585 ++++++++-----------------------------
 iothread.c                         |   9 +-
 nbd/client-connection.c            | 385 ++++++++++++++++++++++++
 stubs/iothread-lock.c              |   2 +-
 stubs/iothread.c                   |   8 -
 tests/unit/iothread.c              |   9 +-
 tests/unit/test-aio.c              |  37 +++
 util/async.c                       |  20 ++
 util/main-loop.c                   |   1 +
 util/qemu-sockets.c                |  19 ++
 nbd/meson.build                    |   1 +
 stubs/meson.build                  |   1 -
 18 files changed, 639 insertions(+), 491 deletions(-)
 create mode 100644 nbd/client-connection.c
 delete mode 100644 stubs/iothread.c

-- 
2.31.1

[PULL 01/34] async: the main AioContext is only "current" if under the BQL

[Eric Blake]

From: Paolo Bonzini <pbonzini@redhat.com>

If we want to wake up a coroutine from a worker thread, aio_co_wake()
currently does not work.  In that scenario, aio_co_wake() calls
aio_co_enter(), but there is no current AioContext and therefore
qemu_get_current_aio_context() returns the main thread.  aio_co_wake()
then attempts to call aio_context_acquire() instead of going through
aio_co_schedule().

The default case of qemu_get_current_aio_context() was added to cover
synchronous I/O started from the vCPU thread, but the main and vCPU
threads are quite different.  The main thread is an I/O thread itself,
only running a more complicated event loop; the vCPU thread instead
is essentially a worker thread that occasionally calls
qemu_mutex_lock_iothread().  It is only in those critical sections
that it acts as if it were the home thread of the main AioContext.

Therefore, this patch detaches qemu_get_current_aio_context() from
iothreads, which is a useless complication.  The AioContext pointer
is stored directly in the thread-local variable, including for the
main loop.  Worker threads (including vCPU threads) optionally behave
as temporary home threads if they have taken the big QEMU lock,
but if that is not the case they will always schedule coroutines
on remote threads via aio_co_schedule().

With this change, the stub qemu_mutex_iothread_locked() must be changed
from true to false.  The previous value of true was needed because the
main thread did not have an AioContext in the thread-local variable,
but now it does have one.

Reported-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210609122234.544153-1-pbonzini@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Tested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: tweak commit message per Vladimir's review]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/aio.h   |  5 ++++-
 iothread.c            |  9 +--------
 stubs/iothread-lock.c |  2 +-
 stubs/iothread.c      |  8 --------
 tests/unit/iothread.c |  9 +--------
 util/async.c          | 20 ++++++++++++++++++++
 util/main-loop.c      |  1 +
 stubs/meson.build     |  1 -
 8 files changed, 28 insertions(+), 27 deletions(-)
 delete mode 100644 stubs/iothread.c

diff --git a/include/block/aio.h b/include/block/aio.h
index 5f342267d5ce..10fcae151540 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -691,10 +691,13 @@ void aio_co_enter(AioContext *ctx, struct Coroutine *co);
  * Return the AioContext whose event loop runs in the current thread.
  *
  * If called from an IOThread this will be the IOThread's AioContext.  If
- * called from another thread it will be the main loop AioContext.
+ * called from the main thread or with the "big QEMU lock" taken it
+ * will be the main loop AioContext.
  */
 AioContext *qemu_get_current_aio_context(void);

+void qemu_set_current_aio_context(AioContext *ctx);
+
 /**
  * aio_context_setup:
  * @ctx: the aio context
diff --git a/iothread.c b/iothread.c
index 7f086387be9a..2c5ccd736733 100644
--- a/iothread.c
+++ b/iothread.c
@@ -39,13 +39,6 @@ DECLARE_CLASS_CHECKERS(IOThreadClass, IOTHREAD,
 #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL
 #endif

-static __thread IOThread *my_iothread;
-
-AioContext *qemu_get_current_aio_context(void)
-{
-    return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
-}
-
 static void *iothread_run(void *opaque)
 {
     IOThread *iothread = opaque;
@@ -56,7 +49,7 @@ static void *iothread_run(void *opaque)
      * in this new thread uses glib.
      */
     g_main_context_push_thread_default(iothread->worker_context);
-    my_iothread = iothread;
+    qemu_set_current_aio_context(iothread->ctx);
     iothread->thread_id = qemu_get_thread_id();
     qemu_sem_post(&iothread->init_done_sem);

diff --git a/stubs/iothread-lock.c b/stubs/iothread-lock.c
index 2a6efad64a16..5b45b7fc8b90 100644
--- a/stubs/iothread-lock.c
+++ b/stubs/iothread-lock.c
@@ -3,7 +3,7 @@

 bool qemu_mutex_iothread_locked(void)
 {
-    return true;
+    return false;
 }

 void qemu_mutex_lock_iothread_impl(const char *file, int line)
diff --git a/stubs/iothread.c b/stubs/iothread.c
deleted file mode 100644
index 8cc9e28c5555..000000000000
--- a/stubs/iothread.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include "qemu/osdep.h"
-#include "block/aio.h"
-#include "qemu/main-loop.h"
-
-AioContext *qemu_get_current_aio_context(void)
-{
-    return qemu_get_aio_context();
-}
diff --git a/tests/unit/iothread.c b/tests/unit/iothread.c
index afde12b4efb5..f9b0791084e7 100644
--- a/tests/unit/iothread.c
+++ b/tests/unit/iothread.c
@@ -30,13 +30,6 @@ struct IOThread {
     bool stopping;
 };

-static __thread IOThread *my_iothread;
-
-AioContext *qemu_get_current_aio_context(void)
-{
-    return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
-}
-
 static void iothread_init_gcontext(IOThread *iothread)
 {
     GSource *source;
@@ -54,9 +47,9 @@ static void *iothread_run(void *opaque)

     rcu_register_thread();

-    my_iothread = iothread;
     qemu_mutex_lock(&iothread->init_done_lock);
     iothread->ctx = aio_context_new(&error_abort);
+    qemu_set_current_aio_context(iothread->ctx);

     /*
      * We must connect the ctx to a GMainContext, because in older versions
diff --git a/util/async.c b/util/async.c
index 674dbefb7c24..5d9b7cc1eba2 100644
--- a/util/async.c
+++ b/util/async.c
@@ -649,3 +649,23 @@ void aio_context_release(AioContext *ctx)
 {
     qemu_rec_mutex_unlock(&ctx->lock);
 }
+
+static __thread AioContext *my_aiocontext;
+
+AioContext *qemu_get_current_aio_context(void)
+{
+    if (my_aiocontext) {
+        return my_aiocontext;
+    }
+    if (qemu_mutex_iothread_locked()) {
+        /* Possibly in a vCPU thread.  */
+        return qemu_get_aio_context();
+    }
+    return NULL;
+}
+
+void qemu_set_current_aio_context(AioContext *ctx)
+{
+    assert(!my_aiocontext);
+    my_aiocontext = ctx;
+}
diff --git a/util/main-loop.c b/util/main-loop.c
index d9c55df6f5e7..4ae5b23e991e 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -170,6 +170,7 @@ int qemu_init_main_loop(Error **errp)
     if (!qemu_aio_context) {
         return -EMFILE;
     }
+    qemu_set_current_aio_context(qemu_aio_context);
     qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
     gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
     src = aio_get_g_source(qemu_aio_context);
diff --git a/stubs/meson.build b/stubs/meson.build
index 65c22c0568ce..4993797f0550 100644
--- a/stubs/meson.build
+++ b/stubs/meson.build
@@ -16,7 +16,6 @@ stub_ss.add(files('fw_cfg.c'))
 stub_ss.add(files('gdbstub.c'))
 stub_ss.add(files('get-vm-name.c'))
 stub_ss.add(when: 'CONFIG_LINUX_IO_URING', if_true: files('io_uring.c'))
-stub_ss.add(files('iothread.c'))
 stub_ss.add(files('iothread-lock.c'))
 stub_ss.add(files('isa-bus.c'))
 stub_ss.add(files('is-daemonized.c'))
-- 
2.31.1

[PULL 02/34] tests: cover aio_co_enter from a worker thread without BQL taken

[Eric Blake]

From: Paolo Bonzini <pbonzini@redhat.com>

Add a testcase for the test fixed by commit 'async: the main AioContext
is only "current" if under the BQL.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210614110214.726722-1-pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 tests/unit/test-aio.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/tests/unit/test-aio.c b/tests/unit/test-aio.c
index 8a4607846340..6feeb9a4a9fd 100644
--- a/tests/unit/test-aio.c
+++ b/tests/unit/test-aio.c
@@ -877,6 +877,42 @@ static void test_queue_chaining(void)
     g_assert_cmpint(data_b.i, ==, data_b.max);
 }

+static void co_check_current_thread(void *opaque)
+{
+    QemuThread *main_thread = opaque;
+    assert(qemu_thread_is_self(main_thread));
+}
+
+static void *test_aio_co_enter(void *co)
+{
+    /*
+     * qemu_get_current_aio_context() should not to be the main thread
+     * AioContext, because this is a worker thread that has not taken
+     * the BQL.  So aio_co_enter will schedule the coroutine in the
+     * main thread AioContext.
+     */
+    aio_co_enter(qemu_get_aio_context(), co);
+    return NULL;
+}
+
+static void test_worker_thread_co_enter(void)
+{
+    QemuThread this_thread, worker_thread;
+    Coroutine *co;
+
+    qemu_thread_get_self(&this_thread);
+    co = qemu_coroutine_create(co_check_current_thread, &this_thread);
+
+    qemu_thread_create(&worker_thread, "test_acquire_thread",
+                       test_aio_co_enter,
+                       co, QEMU_THREAD_JOINABLE);
+
+    /* Test aio_co_enter from a worker thread.  */
+    qemu_thread_join(&worker_thread);
+    g_assert(aio_poll(ctx, true));
+    g_assert(!aio_poll(ctx, false));
+}
+
 /* End of tests.  */

 int main(int argc, char **argv)
@@ -903,6 +939,7 @@ int main(int argc, char **argv)
     g_test_add_func("/aio/timer/schedule",          test_timer_schedule);

     g_test_add_func("/aio/coroutine/queue-chaining", test_queue_chaining);
+    g_test_add_func("/aio/coroutine/worker-thread-co-enter", test_worker_thread_co_enter);

     g_test_add_func("/aio-gsource/flush",                   test_source_flush);
     g_test_add_func("/aio-gsource/bh/schedule",             test_source_bh_schedule);
-- 
2.31.1

[PULL 03/34] co-queue: drop extra coroutine_fn marks

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

qemu_co_queue_next() and qemu_co_queue_restart_all() just call
aio_co_wake() which works well in non-coroutine context. So these
functions can be called from non-coroutine context as well. And
actually qemu_co_queue_restart_all() is called from
nbd_cancel_in_flight(), which is called from non-coroutine context.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-2-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/qemu/coroutine.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index 292e61aef0c2..4829ff373d3c 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -210,13 +210,15 @@ void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock);
 /**
  * Removes the next coroutine from the CoQueue, and wake it up.
  * Returns true if a coroutine was removed, false if the queue is empty.
+ * OK to run from coroutine and non-coroutine context.
  */
-bool coroutine_fn qemu_co_queue_next(CoQueue *queue);
+bool qemu_co_queue_next(CoQueue *queue);

 /**
  * Empties the CoQueue; all coroutines are woken up.
+ * OK to run from coroutine and non-coroutine context.
  */
-void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue);
+void qemu_co_queue_restart_all(CoQueue *queue);

 /**
  * Removes the next coroutine from the CoQueue, and wake it up.  Unlike
-- 
2.31.1

[PULL 04/34] block/nbd: fix channel object leak

[Eric Blake]

From: Roman Kagan <rvkagan@yandex-team.ru>

nbd_free_connect_thread leaks the channel object if it hasn't been
stolen.

Unref it and fix the leak.

Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-3-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/nbd.c b/block/nbd.c
index 616f9ae6c4da..f4b3407587df 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -381,6 +381,7 @@ static void nbd_free_connect_thread(NBDConnectThread *thr)
 {
     if (thr->sioc) {
         qio_channel_close(QIO_CHANNEL(thr->sioc), NULL);
+        object_unref(OBJECT(thr->sioc));
     }
     error_free(thr->err);
     qapi_free_SocketAddress(thr->saddr);
-- 
2.31.1

[PULL 05/34] block/nbd: fix how state is cleared on nbd_open() failure paths

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We have two "return error" paths in nbd_open() after
nbd_process_options(). Actually we should call nbd_clear_bdrvstate()
on these paths. Interesting that nbd_process_options() calls
nbd_clear_bdrvstate() by itself.

Let's fix leaks and refactor things to be more obvious:

- intialize yank at top of nbd_open()
- move yank cleanup to nbd_clear_bdrvstate()
- refactor nbd_open() so that all failure paths except for
  yank-register goes through nbd_clear_bdrvstate()

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-4-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index f4b3407587df..01d2c2efad63 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -152,8 +152,12 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
 static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
 static void nbd_yank(void *opaque);

-static void nbd_clear_bdrvstate(BDRVNBDState *s)
+static void nbd_clear_bdrvstate(BlockDriverState *bs)
 {
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+
+    yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
+
     object_unref(OBJECT(s->tlscreds));
     qapi_free_SocketAddress(s->saddr);
     s->saddr = NULL;
@@ -2275,9 +2279,6 @@ static int nbd_process_options(BlockDriverState *bs, QDict *options,
     ret = 0;

  error:
-    if (ret < 0) {
-        nbd_clear_bdrvstate(s);
-    }
     qemu_opts_del(opts);
     return ret;
 }
@@ -2288,11 +2289,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     int ret;
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;

-    ret = nbd_process_options(bs, options, errp);
-    if (ret < 0) {
-        return ret;
-    }
-
     s->bs = bs;
     qemu_co_mutex_init(&s->send_mutex);
     qemu_co_queue_init(&s->free_sema);
@@ -2301,20 +2297,23 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         return -EEXIST;
     }

+    ret = nbd_process_options(bs, options, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
     /*
      * establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
      */
     if (nbd_establish_connection(bs, s->saddr, errp) < 0) {
-        yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
-        return -ECONNREFUSED;
+        ret = -ECONNREFUSED;
+        goto fail;
     }

     ret = nbd_client_handshake(bs, errp);
     if (ret < 0) {
-        yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
-        nbd_clear_bdrvstate(s);
-        return ret;
+        goto fail;
     }
     /* successfully connected */
     s->state = NBD_CLIENT_CONNECTED;
@@ -2326,6 +2325,10 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);

     return 0;
+
+fail:
+    nbd_clear_bdrvstate(bs);
+    return ret;
 }

 static int nbd_co_flush(BlockDriverState *bs)
@@ -2369,11 +2372,8 @@ static void nbd_refresh_limits(BlockDriverState *bs, Error **errp)

 static void nbd_close(BlockDriverState *bs)
 {
-    BDRVNBDState *s = bs->opaque;
-
     nbd_client_close(bs);
-    yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
-    nbd_clear_bdrvstate(s);
+    nbd_clear_bdrvstate(bs);
 }

 /*
-- 
2.31.1

[PULL 06/34] block/nbd: connect_thread_func(): do qio_channel_set_delay(false)

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

nbd_open() does it (through nbd_establish_connection()).
Actually we lost that call on reconnect path in 1dc4718d849e1a1fe
"block/nbd: use non-blocking connect: fix vm hang on connect()"
when we have introduced reconnect thread.

Fixes: 1dc4718d849e1a1fe665ce5241ed79048cfa2cfc
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-5-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/nbd.c b/block/nbd.c
index 01d2c2efad63..f3a036354dc7 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -408,6 +408,8 @@ static void *connect_thread_func(void *opaque)
         thr->sioc = NULL;
     }

+    qio_channel_set_delay(QIO_CHANNEL(thr->sioc), false);
+
     qemu_mutex_lock(&thr->mutex);

     switch (thr->state) {
-- 
2.31.1

[PULL 07/34] qemu-sockets: introduce socket_address_parse_named_fd()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Add function that transforms named fd inside SocketAddress structure
into number representation. This way it may be then used in a context
where current monitor is not available.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-6-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: comment tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/qemu/sockets.h | 11 +++++++++++
 util/qemu-sockets.c    | 19 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h
index 7d1f8135767d..0c34bf23987e 100644
--- a/include/qemu/sockets.h
+++ b/include/qemu/sockets.h
@@ -111,4 +111,15 @@ SocketAddress *socket_remote_address(int fd, Error **errp);
  */
 SocketAddress *socket_address_flatten(SocketAddressLegacy *addr);

+/**
+ * socket_address_parse_named_fd:
+ *
+ * Modify @addr, replacing a named fd by its corresponding number.
+ * Needed for callers that plan to pass @addr to a context where the
+ * current monitor is not available.
+ *
+ * Return 0 on success.
+ */
+int socket_address_parse_named_fd(SocketAddress *addr, Error **errp);
+
 #endif /* QEMU_SOCKETS_H */
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index c415c342c12b..080a240b74ee 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -1164,6 +1164,25 @@ static int socket_get_fd(const char *fdstr, Error **errp)
     return fd;
 }

+int socket_address_parse_named_fd(SocketAddress *addr, Error **errp)
+{
+    int fd;
+
+    if (addr->type != SOCKET_ADDRESS_TYPE_FD) {
+        return 0;
+    }
+
+    fd = socket_get_fd(addr->u.fd.str, errp);
+    if (fd < 0) {
+        return fd;
+    }
+
+    g_free(addr->u.fd.str);
+    addr->u.fd.str = g_strdup_printf("%d", fd);
+
+    return 0;
+}
+
 int socket_connect(SocketAddress *addr, Error **errp)
 {
     int fd;
-- 
2.31.1

[PULL 08/34] block/nbd: call socket_address_parse_named_fd() in advance

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Detecting monitor by current coroutine works bad when we are not in
coroutine context. And that's exactly so in nbd reconnect code, where
qio_channel_socket_connect_sync() is called from thread.

Monitor is needed only to parse named file descriptor. So, let's just
parse it during nbd_open(), so that all further users of s->saddr don't
need to access monitor.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-7-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/nbd.c b/block/nbd.c
index f3a036354dc7..1c99654ef7e5 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -2140,6 +2140,12 @@ static SocketAddress *nbd_config(BDRVNBDState *s, QDict *options,
         goto done;
     }

+    if (socket_address_parse_named_fd(saddr, errp) < 0) {
+        qapi_free_SocketAddress(saddr);
+        saddr = NULL;
+        goto done;
+    }
+
 done:
     qobject_unref(addr);
     visit_free(iv);
-- 
2.31.1

[PULL 09/34] block/nbd: ensure ->connection_thread is always valid

[Eric Blake]

From: Roman Kagan <rvkagan@yandex-team.ru>

Simplify lifetime management of BDRVNBDState->connect_thread by
delaying the possible cleanup of it until the BDRVNBDState itself goes
away.

This also reverts
 0267101af6 "block/nbd: fix possible use after free of s->connect_thread"
as now s->connect_thread can't be cleared until the very end.

Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
 [vsementsov: rebase, revert 0267101af6 changes]
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
 [eblake: tweak comment]
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-8-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 56 ++++++++++++++++++++---------------------------------
 1 file changed, 21 insertions(+), 35 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 1c99654ef7e5..08ae47d83c07 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -144,17 +144,31 @@ typedef struct BDRVNBDState {
     NBDConnectThread *connect_thread;
 } BDRVNBDState;

+static void nbd_free_connect_thread(NBDConnectThread *thr);
 static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
                                     Error **errp);
 static int nbd_co_establish_connection(BlockDriverState *bs, Error **errp);
-static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
-                                               bool detach);
+static void nbd_co_establish_connection_cancel(BlockDriverState *bs);
 static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
 static void nbd_yank(void *opaque);

 static void nbd_clear_bdrvstate(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    NBDConnectThread *thr = s->connect_thread;
+    bool thr_running;
+
+    qemu_mutex_lock(&thr->mutex);
+    thr_running = thr->state == CONNECT_THREAD_RUNNING;
+    if (thr_running) {
+        thr->state = CONNECT_THREAD_RUNNING_DETACHED;
+    }
+    qemu_mutex_unlock(&thr->mutex);
+
+    /* the runaway thread will clean up itself */
+    if (!thr_running) {
+        nbd_free_connect_thread(thr);
+    }

     yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));

@@ -295,7 +309,7 @@ static void coroutine_fn nbd_client_co_drain_begin(BlockDriverState *bs)
     s->drained = true;
     qemu_co_sleep_wake(&s->reconnect_sleep);

-    nbd_co_establish_connection_cancel(bs, false);
+    nbd_co_establish_connection_cancel(bs);

     reconnect_delay_timer_del(s);

@@ -333,7 +347,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
     s->state = NBD_CLIENT_QUIT;
     if (s->connection_co) {
         qemu_co_sleep_wake(&s->reconnect_sleep);
-        nbd_co_establish_connection_cancel(bs, true);
+        nbd_co_establish_connection_cancel(bs);
     }
     if (qemu_in_coroutine()) {
         s->teardown_co = qemu_coroutine_self();
@@ -446,11 +460,6 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
     BDRVNBDState *s = bs->opaque;
     NBDConnectThread *thr = s->connect_thread;

-    if (!thr) {
-        /* detached */
-        return -1;
-    }
-
     qemu_mutex_lock(&thr->mutex);

     switch (thr->state) {
@@ -494,12 +503,6 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
     s->wait_connect = true;
     qemu_coroutine_yield();

-    if (!s->connect_thread) {
-        /* detached */
-        return -1;
-    }
-    assert(thr == s->connect_thread);
-
     qemu_mutex_lock(&thr->mutex);

     switch (thr->state) {
@@ -547,18 +550,12 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
  * nbd_co_establish_connection_cancel
  * Cancel nbd_co_establish_connection asynchronously: it will finish soon, to
  * allow drained section to begin.
- *
- * If detach is true, also cleanup the state (or if thread is running, move it
- * to CONNECT_THREAD_RUNNING_DETACHED state). s->connect_thread becomes NULL if
- * detach is true.
  */
-static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
-                                               bool detach)
+static void nbd_co_establish_connection_cancel(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
     NBDConnectThread *thr = s->connect_thread;
     bool wake = false;
-    bool do_free = false;

     qemu_mutex_lock(&thr->mutex);

@@ -569,21 +566,10 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
             s->wait_connect = false;
             wake = true;
         }
-        if (detach) {
-            thr->state = CONNECT_THREAD_RUNNING_DETACHED;
-            s->connect_thread = NULL;
-        }
-    } else if (detach) {
-        do_free = true;
     }

     qemu_mutex_unlock(&thr->mutex);

-    if (do_free) {
-        nbd_free_connect_thread(thr);
-        s->connect_thread = NULL;
-    }
-
     if (wake) {
         aio_co_wake(s->connection_co);
     }
@@ -2310,6 +2296,8 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }

+    nbd_init_connect_thread(s);
+
     /*
      * establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
@@ -2326,8 +2314,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     /* successfully connected */
     s->state = NBD_CLIENT_CONNECTED;

-    nbd_init_connect_thread(s);
-
     s->connection_co = qemu_coroutine_create(nbd_connection_entry, s);
     bdrv_inc_in_flight(bs);
     aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);
-- 
2.31.1

[PULL 10/34] block/nbd: nbd_client_handshake(): fix leak of s->ioc

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Message-Id: <20210610100802.5888-9-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/nbd.c b/block/nbd.c
index 08ae47d83c07..77b85ca47189 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1889,6 +1889,8 @@ static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
                                  nbd_yank, bs);
         object_unref(OBJECT(s->sioc));
         s->sioc = NULL;
+        object_unref(OBJECT(s->ioc));
+        s->ioc = NULL;

         return ret;
     }
-- 
2.31.1

[PULL 11/34] block/nbd: BDRVNBDState: drop unused connect_err and connect_status

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

These fields are write-only. Drop them.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-10-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 77b85ca47189..fdfb1ff7a158 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -121,8 +121,6 @@ typedef struct BDRVNBDState {
     bool wait_drained_end;
     int in_flight;
     NBDClientState state;
-    int connect_status;
-    Error *connect_err;
     bool wait_in_flight;

     QEMUTimer *reconnect_delay_timer;
@@ -578,7 +576,6 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs)
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
-    Error *local_err = NULL;

     if (!nbd_client_connecting(s)) {
         return;
@@ -619,14 +616,14 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    if (nbd_co_establish_connection(s->bs, &local_err) < 0) {
+    if (nbd_co_establish_connection(s->bs, NULL) < 0) {
         ret = -ECONNREFUSED;
         goto out;
     }

     bdrv_dec_in_flight(s->bs);

-    ret = nbd_client_handshake(s->bs, &local_err);
+    ret = nbd_client_handshake(s->bs, NULL);

     if (s->drained) {
         s->wait_drained_end = true;
@@ -641,11 +638,6 @@ 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 (ret >= 0) {
         /* successfully connected */
         s->state = NBD_CLIENT_CONNECTED;
-- 
2.31.1

[PULL 12/34] block/nbd: simplify waking of nbd_co_establish_connection()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Instead of managing connect_bh, bh_ctx, and wait_connect fields, we
can use a single link to the waiting coroutine with proper mutex
protection.

So new logic is:

nbd_co_establish_connection() sets wait_co under the mutex, releases
the mutex, then yield()s.  Note that wait_co may be scheduled by the
thread immediately after unlocking the mutex.  Still, the main thread
(or iothread) will not reach the code for entering the coroutine until
the yield(), so we are safe.

connect_thread_func() and nbd_co_establish_connection_cancel() do
the following to handle wait_co:

Under the mutex, if thr->wait_co is not NULL, make it NULL and
schedule it. This way, we avoid scheduling the coroutine twice.

Still scheduling is a bit different:

In connect_thread_func() we can just call aio_co_wake under mutex,
after commit
   [async: the main AioContext is only "current" if under the BQL]
we are sure that aio_co_wake() will not try to acquire the aio context
and do qemu_aio_coroutine_enter() but simply schedule the coroutine by
aio_co_schedule().

nbd_co_establish_connection_cancel() will be called from non-coroutine
context in further patch and will be able to go through
qemu_aio_coroutine_enter() path of aio_co_wake(). So keep current
behavior of waking the coroutine after the critical section.

Also, this commit reduces the dependence of
nbd_co_establish_connection() on the internals of bs (we now use a
generic pointer to the coroutine, instead of direct use of
s->connection_co).  This is a step towards splitting the connection
API out of nbd.c.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-11-vsementsov@virtuozzo.com>
Reviewied-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 55 +++++++++++++++--------------------------------------
 1 file changed, 15 insertions(+), 40 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index fdfb1ff7a158..653af629408d 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -87,12 +87,6 @@ typedef enum NBDConnectThreadState {
 typedef struct NBDConnectThread {
     /* Initialization constants */
     SocketAddress *saddr; /* address to connect to */
-    /*
-     * Bottom half to schedule on completion. Scheduled only if bh_ctx is not
-     * NULL
-     */
-    QEMUBHFunc *bh_func;
-    void *bh_opaque;

     /*
      * Result of last attempt. Valid in FAIL and SUCCESS states.
@@ -101,10 +95,15 @@ typedef struct NBDConnectThread {
     QIOChannelSocket *sioc;
     Error *err;

-    /* state and bh_ctx are protected by mutex */
     QemuMutex mutex;
+    /* All further fields are protected by mutex */
     NBDConnectThreadState state; /* current state of the thread */
-    AioContext *bh_ctx; /* where to schedule bh (NULL means don't schedule) */
+
+    /*
+     * wait_co: if non-NULL, which coroutine to wake in
+     * nbd_co_establish_connection() after yield()
+     */
+    Coroutine *wait_co;
 } NBDConnectThread;

 typedef struct BDRVNBDState {
@@ -138,7 +137,6 @@ typedef struct BDRVNBDState {
     char *x_dirty_bitmap;
     bool alloc_depth;

-    bool wait_connect;
     NBDConnectThread *connect_thread;
 } BDRVNBDState;

@@ -370,15 +368,6 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)
     return qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTING_WAIT;
 }

-static void connect_bh(void *opaque)
-{
-    BDRVNBDState *state = opaque;
-
-    assert(state->wait_connect);
-    state->wait_connect = false;
-    aio_co_wake(state->connection_co);
-}
-
 static void nbd_init_connect_thread(BDRVNBDState *s)
 {
     s->connect_thread = g_new(NBDConnectThread, 1);
@@ -386,8 +375,6 @@ static void nbd_init_connect_thread(BDRVNBDState *s)
     *s->connect_thread = (NBDConnectThread) {
         .saddr = QAPI_CLONE(SocketAddress, s->saddr),
         .state = CONNECT_THREAD_NONE,
-        .bh_func = connect_bh,
-        .bh_opaque = s,
     };

     qemu_mutex_init(&s->connect_thread->mutex);
@@ -427,11 +414,9 @@ static void *connect_thread_func(void *opaque)
     switch (thr->state) {
     case CONNECT_THREAD_RUNNING:
         thr->state = ret < 0 ? CONNECT_THREAD_FAIL : CONNECT_THREAD_SUCCESS;
-        if (thr->bh_ctx) {
-            aio_bh_schedule_oneshot(thr->bh_ctx, thr->bh_func, thr->bh_opaque);
-
-            /* play safe, don't reuse bh_ctx on further connection attempts */
-            thr->bh_ctx = NULL;
+        if (thr->wait_co) {
+            aio_co_wake(thr->wait_co);
+            thr->wait_co = NULL;
         }
         break;
     case CONNECT_THREAD_RUNNING_DETACHED:
@@ -485,20 +470,14 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
         abort();
     }

-    thr->bh_ctx = qemu_get_current_aio_context();
+    thr->wait_co = qemu_coroutine_self();

     qemu_mutex_unlock(&thr->mutex);

-
     /*
      * We are going to wait for connect-thread finish, but
      * nbd_client_co_drain_begin() can interrupt.
-     *
-     * Note that wait_connect variable is not visible for connect-thread. It
-     * doesn't need mutex protection, it used only inside home aio context of
-     * bs.
      */
-    s->wait_connect = true;
     qemu_coroutine_yield();

     qemu_mutex_lock(&thr->mutex);
@@ -553,23 +532,19 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
     NBDConnectThread *thr = s->connect_thread;
-    bool wake = false;
+    Coroutine *wait_co = NULL;

     qemu_mutex_lock(&thr->mutex);

     if (thr->state == CONNECT_THREAD_RUNNING) {
         /* We can cancel only in running state, when bh is not yet scheduled */
-        thr->bh_ctx = NULL;
-        if (s->wait_connect) {
-            s->wait_connect = false;
-            wake = true;
-        }
+        wait_co = g_steal_pointer(&thr->wait_co);
     }

     qemu_mutex_unlock(&thr->mutex);

-    if (wake) {
-        aio_co_wake(s->connection_co);
+    if (wait_co) {
+        aio_co_wake(wait_co);
     }
 }

-- 
2.31.1

[PULL 13/34] block/nbd: drop thr->state

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We don't need all these states. The code refactored to use two boolean
variables looks simpler.

While moving the comment in nbd_co_establish_connection() rework it to
give better information. Also, we are going to move the connection code
to separate file and mentioning drained section would be confusing.

Improve also the comment in NBDConnectThread, while dropping removed
state names from it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-12-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: comment tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 148 +++++++++++++++++-----------------------------------
 1 file changed, 49 insertions(+), 99 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 653af629408d..f2d5b47026a3 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -66,38 +66,25 @@ typedef enum NBDClientState {
     NBD_CLIENT_QUIT
 } NBDClientState;

-typedef enum NBDConnectThreadState {
-    /* No thread, no pending results */
-    CONNECT_THREAD_NONE,
-
-    /* Thread is running, no results for now */
-    CONNECT_THREAD_RUNNING,
-
-    /*
-     * Thread is running, but requestor exited. Thread should close
-     * the new socket and free the connect state on exit.
-     */
-    CONNECT_THREAD_RUNNING_DETACHED,
-
-    /* Thread finished, results are stored in a state */
-    CONNECT_THREAD_FAIL,
-    CONNECT_THREAD_SUCCESS
-} NBDConnectThreadState;
-
 typedef struct NBDConnectThread {
     /* Initialization constants */
     SocketAddress *saddr; /* address to connect to */

-    /*
-     * Result of last attempt. Valid in FAIL and SUCCESS states.
-     * If you want to steal error, don't forget to set pointer to NULL.
-     */
-    QIOChannelSocket *sioc;
-    Error *err;
-
     QemuMutex mutex;
-    /* All further fields are protected by mutex */
-    NBDConnectThreadState state; /* current state of the thread */
+
+    /*
+     * @sioc and @err represent a connection attempt.  While running
+     * is true, they are only used by the connection thread, and mutex
+     * locking is not needed.  Once the thread finishes,
+     * nbd_co_establish_connection then steals these pointers while
+     * under the mutex.
+     */
+    QIOChannelSocket *sioc;
+    Error *err;
+
+    /* All further fields are accessed only under mutex */
+    bool running; /* thread is running now */
+    bool detached; /* thread is detached and should cleanup the state */

     /*
      * wait_co: if non-NULL, which coroutine to wake in
@@ -152,17 +139,19 @@ static void nbd_clear_bdrvstate(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     NBDConnectThread *thr = s->connect_thread;
-    bool thr_running;
+    bool do_free = false;

     qemu_mutex_lock(&thr->mutex);
-    thr_running = thr->state == CONNECT_THREAD_RUNNING;
-    if (thr_running) {
-        thr->state = CONNECT_THREAD_RUNNING_DETACHED;
+    assert(!thr->detached);
+    if (thr->running) {
+        thr->detached = true;
+    } else {
+        do_free = true;
     }
     qemu_mutex_unlock(&thr->mutex);

     /* the runaway thread will clean up itself */
-    if (!thr_running) {
+    if (do_free) {
         nbd_free_connect_thread(thr);
     }

@@ -374,7 +363,6 @@ static void nbd_init_connect_thread(BDRVNBDState *s)

     *s->connect_thread = (NBDConnectThread) {
         .saddr = QAPI_CLONE(SocketAddress, s->saddr),
-        .state = CONNECT_THREAD_NONE,
     };

     qemu_mutex_init(&s->connect_thread->mutex);
@@ -395,7 +383,7 @@ static void *connect_thread_func(void *opaque)
 {
     NBDConnectThread *thr = opaque;
     int ret;
-    bool do_free = false;
+    bool do_free;

     thr->sioc = qio_channel_socket_new();

@@ -411,20 +399,13 @@ static void *connect_thread_func(void *opaque)

     qemu_mutex_lock(&thr->mutex);

-    switch (thr->state) {
-    case CONNECT_THREAD_RUNNING:
-        thr->state = ret < 0 ? CONNECT_THREAD_FAIL : CONNECT_THREAD_SUCCESS;
-        if (thr->wait_co) {
-            aio_co_wake(thr->wait_co);
-            thr->wait_co = NULL;
-        }
-        break;
-    case CONNECT_THREAD_RUNNING_DETACHED:
-        do_free = true;
-        break;
-    default:
-        abort();
+    assert(thr->running);
+    thr->running = false;
+    if (thr->wait_co) {
+        aio_co_wake(thr->wait_co);
+        thr->wait_co = NULL;
     }
+    do_free = thr->detached;

     qemu_mutex_unlock(&thr->mutex);

@@ -438,36 +419,24 @@ static void *connect_thread_func(void *opaque)
 static int coroutine_fn
 nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
 {
-    int ret;
     QemuThread thread;
     BDRVNBDState *s = bs->opaque;
     NBDConnectThread *thr = s->connect_thread;

+    assert(!s->sioc);
+
     qemu_mutex_lock(&thr->mutex);

-    switch (thr->state) {
-    case CONNECT_THREAD_FAIL:
-    case CONNECT_THREAD_NONE:
+    if (!thr->running) {
+        if (thr->sioc) {
+            /* Previous attempt finally succeeded in background */
+            goto out;
+        }
+        thr->running = true;
         error_free(thr->err);
         thr->err = NULL;
-        thr->state = CONNECT_THREAD_RUNNING;
         qemu_thread_create(&thread, "nbd-connect",
                            connect_thread_func, thr, QEMU_THREAD_DETACHED);
-        break;
-    case CONNECT_THREAD_SUCCESS:
-        /* Previous attempt finally succeeded in background */
-        thr->state = CONNECT_THREAD_NONE;
-        s->sioc = thr->sioc;
-        thr->sioc = NULL;
-        yank_register_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
-                               nbd_yank, bs);
-        qemu_mutex_unlock(&thr->mutex);
-        return 0;
-    case CONNECT_THREAD_RUNNING:
-        /* Already running, will wait */
-        break;
-    default:
-        abort();
     }

     thr->wait_co = qemu_coroutine_self();
@@ -482,10 +451,16 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)

     qemu_mutex_lock(&thr->mutex);

-    switch (thr->state) {
-    case CONNECT_THREAD_SUCCESS:
-    case CONNECT_THREAD_FAIL:
-        thr->state = CONNECT_THREAD_NONE;
+out:
+    if (thr->running) {
+        /*
+         * The connection attempt was canceled and the coroutine resumed
+         * before the connection thread finished its job.  Report the
+         * attempt as failed, but leave the connection thread running,
+         * to reuse it for the next connection attempt.
+         */
+        error_setg(errp, "Connection attempt cancelled by other operation");
+    } else {
         error_propagate(errp, thr->err);
         thr->err = NULL;
         s->sioc = thr->sioc;
@@ -494,33 +469,11 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
             yank_register_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
                                    nbd_yank, bs);
         }
-        ret = (s->sioc ? 0 : -1);
-        break;
-    case CONNECT_THREAD_RUNNING:
-    case CONNECT_THREAD_RUNNING_DETACHED:
-        /*
-         * Obviously, drained section wants to start. Report the attempt as
-         * failed. Still connect thread is executing in background, and its
-         * result may be used for next connection attempt.
-         */
-        ret = -1;
-        error_setg(errp, "Connection attempt cancelled by other operation");
-        break;
-
-    case CONNECT_THREAD_NONE:
-        /*
-         * Impossible. We've seen this thread running. So it should be
-         * running or at least give some results.
-         */
-        abort();
-
-    default:
-        abort();
     }

     qemu_mutex_unlock(&thr->mutex);

-    return ret;
+    return s->sioc ? 0 : -1;
 }

 /*
@@ -532,14 +485,11 @@ static void nbd_co_establish_connection_cancel(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
     NBDConnectThread *thr = s->connect_thread;
-    Coroutine *wait_co = NULL;
+    Coroutine *wait_co;

     qemu_mutex_lock(&thr->mutex);

-    if (thr->state == CONNECT_THREAD_RUNNING) {
-        /* We can cancel only in running state, when bh is not yet scheduled */
-        wait_co = g_steal_pointer(&thr->wait_co);
-    }
+    wait_co = g_steal_pointer(&thr->wait_co);

     qemu_mutex_unlock(&thr->mutex);

-- 
2.31.1

[PULL 14/34] block/nbd: bs-independent interface for nbd_co_establish_connection()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We are going to split connection code to a separate file. Now we are
ready to give nbd_co_establish_connection() clean and bs-independent
interface.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-13-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 50 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index f2d5b47026a3..15b569a899fd 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -130,7 +130,8 @@ typedef struct BDRVNBDState {
 static void nbd_free_connect_thread(NBDConnectThread *thr);
 static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
                                     Error **errp);
-static int nbd_co_establish_connection(BlockDriverState *bs, Error **errp);
+static coroutine_fn QIOChannelSocket *
+nbd_co_establish_connection(NBDConnectThread *thr, Error **errp);
 static void nbd_co_establish_connection_cancel(BlockDriverState *bs);
 static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
 static void nbd_yank(void *opaque);
@@ -416,22 +417,37 @@ static void *connect_thread_func(void *opaque)
     return NULL;
 }

-static int coroutine_fn
-nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
+/*
+ * Get a new connection in context of @thr:
+ *   if the thread is running, wait for completion
+ *   if the thread already succeeded in the background, and user didn't get the
+ *     result, just return it now
+ *   otherwise the thread is not running, so start a thread and wait for
+ *     completion
+ */
+static coroutine_fn QIOChannelSocket *
+nbd_co_establish_connection(NBDConnectThread *thr, Error **errp)
 {
+    QIOChannelSocket *sioc = NULL;
     QemuThread thread;
-    BDRVNBDState *s = bs->opaque;
-    NBDConnectThread *thr = s->connect_thread;
-
-    assert(!s->sioc);

     qemu_mutex_lock(&thr->mutex);

+    /*
+     * Don't call nbd_co_establish_connection() in several coroutines in
+     * parallel. Only one call at once is supported.
+     */
+    assert(!thr->wait_co);
+
     if (!thr->running) {
         if (thr->sioc) {
             /* Previous attempt finally succeeded in background */
-            goto out;
+            sioc = g_steal_pointer(&thr->sioc);
+            qemu_mutex_unlock(&thr->mutex);
+
+            return sioc;
         }
+
         thr->running = true;
         error_free(thr->err);
         thr->err = NULL;
@@ -445,13 +461,12 @@ nbd_co_establish_connection(BlockDriverState *bs, Error **errp)

     /*
      * We are going to wait for connect-thread finish, but
-     * nbd_client_co_drain_begin() can interrupt.
+     * nbd_co_establish_connection_cancel() can interrupt.
      */
     qemu_coroutine_yield();

     qemu_mutex_lock(&thr->mutex);

-out:
     if (thr->running) {
         /*
          * The connection attempt was canceled and the coroutine resumed
@@ -463,17 +478,12 @@ out:
     } else {
         error_propagate(errp, thr->err);
         thr->err = NULL;
-        s->sioc = thr->sioc;
-        thr->sioc = NULL;
-        if (s->sioc) {
-            yank_register_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
-                                   nbd_yank, bs);
-        }
+        sioc = g_steal_pointer(&thr->sioc);
     }

     qemu_mutex_unlock(&thr->mutex);

-    return s->sioc ? 0 : -1;
+    return sioc;
 }

 /*
@@ -541,11 +551,15 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    if (nbd_co_establish_connection(s->bs, NULL) < 0) {
+    s->sioc = nbd_co_establish_connection(s->connect_thread, NULL);
+    if (!s->sioc) {
         ret = -ECONNREFUSED;
         goto out;
     }

+    yank_register_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name), nbd_yank,
+                           s->bs);
+
     bdrv_dec_in_flight(s->bs);

     ret = nbd_client_handshake(s->bs, NULL);
-- 
2.31.1

[PULL 15/34] block/nbd: make nbd_co_establish_connection_cancel() bs-independent

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

nbd_co_establish_connection_cancel() actually needs only pointer to
NBDConnectThread. So, make it clean.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-14-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 15b569a899fd..bee615e5c4c1 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -132,7 +132,7 @@ static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
                                     Error **errp);
 static coroutine_fn QIOChannelSocket *
 nbd_co_establish_connection(NBDConnectThread *thr, Error **errp);
-static void nbd_co_establish_connection_cancel(BlockDriverState *bs);
+static void nbd_co_establish_connection_cancel(NBDConnectThread *thr);
 static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
 static void nbd_yank(void *opaque);

@@ -295,7 +295,7 @@ static void coroutine_fn nbd_client_co_drain_begin(BlockDriverState *bs)
     s->drained = true;
     qemu_co_sleep_wake(&s->reconnect_sleep);

-    nbd_co_establish_connection_cancel(bs);
+    nbd_co_establish_connection_cancel(s->connect_thread);

     reconnect_delay_timer_del(s);

@@ -333,7 +333,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
     s->state = NBD_CLIENT_QUIT;
     if (s->connection_co) {
         qemu_co_sleep_wake(&s->reconnect_sleep);
-        nbd_co_establish_connection_cancel(bs);
+        nbd_co_establish_connection_cancel(s->connect_thread);
     }
     if (qemu_in_coroutine()) {
         s->teardown_co = qemu_coroutine_self();
@@ -488,13 +488,14 @@ nbd_co_establish_connection(NBDConnectThread *thr, Error **errp)

 /*
  * nbd_co_establish_connection_cancel
- * Cancel nbd_co_establish_connection asynchronously: it will finish soon, to
- * allow drained section to begin.
+ * Cancel nbd_co_establish_connection() asynchronously.
+ *
+ * Note that this function neither directly stops the thread nor closes the
+ * socket, but rather safely wakes nbd_co_establish_connection() which is
+ * sleeping in yield()
  */
-static void nbd_co_establish_connection_cancel(BlockDriverState *bs)
+static void nbd_co_establish_connection_cancel(NBDConnectThread *thr)
 {
-    BDRVNBDState *s = bs->opaque;
-    NBDConnectThread *thr = s->connect_thread;
     Coroutine *wait_co;

     qemu_mutex_lock(&thr->mutex);
-- 
2.31.1

[PULL 16/34] block/nbd: rename NBDConnectThread to NBDClientConnection

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We are going to move the connection code to its own file, and want
clear names and APIs first.

The structure is shared between user and (possibly) several runs of
connect-thread. So it's wrong to call it "thread". Let's rename to
something more generic.

Appropriately rename connect_thread and thr variables to conn.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-15-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 134 ++++++++++++++++++++++++++--------------------------
 1 file changed, 67 insertions(+), 67 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index bee615e5c4c1..ce8d38d17abf 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -66,7 +66,7 @@ typedef enum NBDClientState {
     NBD_CLIENT_QUIT
 } NBDClientState;

-typedef struct NBDConnectThread {
+typedef struct NBDClientConnection {
     /* Initialization constants */
     SocketAddress *saddr; /* address to connect to */

@@ -91,7 +91,7 @@ typedef struct NBDConnectThread {
      * nbd_co_establish_connection() after yield()
      */
     Coroutine *wait_co;
-} NBDConnectThread;
+} NBDClientConnection;

 typedef struct BDRVNBDState {
     QIOChannelSocket *sioc; /* The master data channel */
@@ -124,36 +124,36 @@ typedef struct BDRVNBDState {
     char *x_dirty_bitmap;
     bool alloc_depth;

-    NBDConnectThread *connect_thread;
+    NBDClientConnection *conn;
 } BDRVNBDState;

-static void nbd_free_connect_thread(NBDConnectThread *thr);
+static void nbd_free_connect_thread(NBDClientConnection *conn);
 static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
                                     Error **errp);
 static coroutine_fn QIOChannelSocket *
-nbd_co_establish_connection(NBDConnectThread *thr, Error **errp);
-static void nbd_co_establish_connection_cancel(NBDConnectThread *thr);
+nbd_co_establish_connection(NBDClientConnection *conn, Error **errp);
+static void nbd_co_establish_connection_cancel(NBDClientConnection *conn);
 static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
 static void nbd_yank(void *opaque);

 static void nbd_clear_bdrvstate(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
-    NBDConnectThread *thr = s->connect_thread;
+    NBDClientConnection *conn = s->conn;
     bool do_free = false;

-    qemu_mutex_lock(&thr->mutex);
-    assert(!thr->detached);
-    if (thr->running) {
-        thr->detached = true;
+    qemu_mutex_lock(&conn->mutex);
+    assert(!conn->detached);
+    if (conn->running) {
+        conn->detached = true;
     } else {
         do_free = true;
     }
-    qemu_mutex_unlock(&thr->mutex);
+    qemu_mutex_unlock(&conn->mutex);

     /* the runaway thread will clean up itself */
     if (do_free) {
-        nbd_free_connect_thread(thr);
+        nbd_free_connect_thread(conn);
     }

     yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));
@@ -295,7 +295,7 @@ static void coroutine_fn nbd_client_co_drain_begin(BlockDriverState *bs)
     s->drained = true;
     qemu_co_sleep_wake(&s->reconnect_sleep);

-    nbd_co_establish_connection_cancel(s->connect_thread);
+    nbd_co_establish_connection_cancel(s->conn);

     reconnect_delay_timer_del(s);

@@ -333,7 +333,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
     s->state = NBD_CLIENT_QUIT;
     if (s->connection_co) {
         qemu_co_sleep_wake(&s->reconnect_sleep);
-        nbd_co_establish_connection_cancel(s->connect_thread);
+        nbd_co_establish_connection_cancel(s->conn);
     }
     if (qemu_in_coroutine()) {
         s->teardown_co = qemu_coroutine_self();
@@ -360,65 +360,65 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)

 static void nbd_init_connect_thread(BDRVNBDState *s)
 {
-    s->connect_thread = g_new(NBDConnectThread, 1);
+    s->conn = g_new(NBDClientConnection, 1);

-    *s->connect_thread = (NBDConnectThread) {
+    *s->conn = (NBDClientConnection) {
         .saddr = QAPI_CLONE(SocketAddress, s->saddr),
     };

-    qemu_mutex_init(&s->connect_thread->mutex);
+    qemu_mutex_init(&s->conn->mutex);
 }

-static void nbd_free_connect_thread(NBDConnectThread *thr)
+static void nbd_free_connect_thread(NBDClientConnection *conn)
 {
-    if (thr->sioc) {
-        qio_channel_close(QIO_CHANNEL(thr->sioc), NULL);
-        object_unref(OBJECT(thr->sioc));
+    if (conn->sioc) {
+        qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
+        object_unref(OBJECT(conn->sioc));
     }
-    error_free(thr->err);
-    qapi_free_SocketAddress(thr->saddr);
-    g_free(thr);
+    error_free(conn->err);
+    qapi_free_SocketAddress(conn->saddr);
+    g_free(conn);
 }

 static void *connect_thread_func(void *opaque)
 {
-    NBDConnectThread *thr = opaque;
+    NBDClientConnection *conn = opaque;
     int ret;
     bool do_free;

-    thr->sioc = qio_channel_socket_new();
+    conn->sioc = qio_channel_socket_new();

-    error_free(thr->err);
-    thr->err = NULL;
-    ret = qio_channel_socket_connect_sync(thr->sioc, thr->saddr, &thr->err);
+    error_free(conn->err);
+    conn->err = NULL;
+    ret = qio_channel_socket_connect_sync(conn->sioc, conn->saddr, &conn->err);
     if (ret < 0) {
-        object_unref(OBJECT(thr->sioc));
-        thr->sioc = NULL;
+        object_unref(OBJECT(conn->sioc));
+        conn->sioc = NULL;
     }

-    qio_channel_set_delay(QIO_CHANNEL(thr->sioc), false);
+    qio_channel_set_delay(QIO_CHANNEL(conn->sioc), false);

-    qemu_mutex_lock(&thr->mutex);
+    qemu_mutex_lock(&conn->mutex);

-    assert(thr->running);
-    thr->running = false;
-    if (thr->wait_co) {
-        aio_co_wake(thr->wait_co);
-        thr->wait_co = NULL;
+    assert(conn->running);
+    conn->running = false;
+    if (conn->wait_co) {
+        aio_co_wake(conn->wait_co);
+        conn->wait_co = NULL;
     }
-    do_free = thr->detached;
+    do_free = conn->detached;

-    qemu_mutex_unlock(&thr->mutex);
+    qemu_mutex_unlock(&conn->mutex);

     if (do_free) {
-        nbd_free_connect_thread(thr);
+        nbd_free_connect_thread(conn);
     }

     return NULL;
 }

 /*
- * Get a new connection in context of @thr:
+ * Get a new connection in context of @conn:
  *   if the thread is running, wait for completion
  *   if the thread already succeeded in the background, and user didn't get the
  *     result, just return it now
@@ -426,38 +426,38 @@ static void *connect_thread_func(void *opaque)
  *     completion
  */
 static coroutine_fn QIOChannelSocket *
-nbd_co_establish_connection(NBDConnectThread *thr, Error **errp)
+nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
 {
     QIOChannelSocket *sioc = NULL;
     QemuThread thread;

-    qemu_mutex_lock(&thr->mutex);
+    qemu_mutex_lock(&conn->mutex);

     /*
      * Don't call nbd_co_establish_connection() in several coroutines in
      * parallel. Only one call at once is supported.
      */
-    assert(!thr->wait_co);
+    assert(!conn->wait_co);

-    if (!thr->running) {
-        if (thr->sioc) {
+    if (!conn->running) {
+        if (conn->sioc) {
             /* Previous attempt finally succeeded in background */
-            sioc = g_steal_pointer(&thr->sioc);
-            qemu_mutex_unlock(&thr->mutex);
+            sioc = g_steal_pointer(&conn->sioc);
+            qemu_mutex_unlock(&conn->mutex);

             return sioc;
         }

-        thr->running = true;
-        error_free(thr->err);
-        thr->err = NULL;
+        conn->running = true;
+        error_free(conn->err);
+        conn->err = NULL;
         qemu_thread_create(&thread, "nbd-connect",
-                           connect_thread_func, thr, QEMU_THREAD_DETACHED);
+                           connect_thread_func, conn, QEMU_THREAD_DETACHED);
     }

-    thr->wait_co = qemu_coroutine_self();
+    conn->wait_co = qemu_coroutine_self();

-    qemu_mutex_unlock(&thr->mutex);
+    qemu_mutex_unlock(&conn->mutex);

     /*
      * We are going to wait for connect-thread finish, but
@@ -465,9 +465,9 @@ nbd_co_establish_connection(NBDConnectThread *thr, Error **errp)
      */
     qemu_coroutine_yield();

-    qemu_mutex_lock(&thr->mutex);
+    qemu_mutex_lock(&conn->mutex);

-    if (thr->running) {
+    if (conn->running) {
         /*
          * The connection attempt was canceled and the coroutine resumed
          * before the connection thread finished its job.  Report the
@@ -476,12 +476,12 @@ nbd_co_establish_connection(NBDConnectThread *thr, Error **errp)
          */
         error_setg(errp, "Connection attempt cancelled by other operation");
     } else {
-        error_propagate(errp, thr->err);
-        thr->err = NULL;
-        sioc = g_steal_pointer(&thr->sioc);
+        error_propagate(errp, conn->err);
+        conn->err = NULL;
+        sioc = g_steal_pointer(&conn->sioc);
     }

-    qemu_mutex_unlock(&thr->mutex);
+    qemu_mutex_unlock(&conn->mutex);

     return sioc;
 }
@@ -494,15 +494,15 @@ nbd_co_establish_connection(NBDConnectThread *thr, Error **errp)
  * socket, but rather safely wakes nbd_co_establish_connection() which is
  * sleeping in yield()
  */
-static void nbd_co_establish_connection_cancel(NBDConnectThread *thr)
+static void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 {
     Coroutine *wait_co;

-    qemu_mutex_lock(&thr->mutex);
+    qemu_mutex_lock(&conn->mutex);

-    wait_co = g_steal_pointer(&thr->wait_co);
+    wait_co = g_steal_pointer(&conn->wait_co);

-    qemu_mutex_unlock(&thr->mutex);
+    qemu_mutex_unlock(&conn->mutex);

     if (wait_co) {
         aio_co_wake(wait_co);
@@ -552,7 +552,7 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    s->sioc = nbd_co_establish_connection(s->connect_thread, NULL);
+    s->sioc = nbd_co_establish_connection(s->conn, NULL);
     if (!s->sioc) {
         ret = -ECONNREFUSED;
         goto out;
-- 
2.31.1

[PULL 17/34] block/nbd: introduce nbd_client_connection_new()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

This is a step of creating bs-independent nbd connection interface.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-16-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index ce8d38d17abf..e7261aeaef7b 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -358,15 +358,18 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)
     return qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTING_WAIT;
 }

-static void nbd_init_connect_thread(BDRVNBDState *s)
+static NBDClientConnection *
+nbd_client_connection_new(const SocketAddress *saddr)
 {
-    s->conn = g_new(NBDClientConnection, 1);
+    NBDClientConnection *conn = g_new(NBDClientConnection, 1);

-    *s->conn = (NBDClientConnection) {
-        .saddr = QAPI_CLONE(SocketAddress, s->saddr),
+    *conn = (NBDClientConnection) {
+        .saddr = QAPI_CLONE(SocketAddress, saddr),
     };

-    qemu_mutex_init(&s->conn->mutex);
+    qemu_mutex_init(&conn->mutex);
+
+    return conn;
 }

 static void nbd_free_connect_thread(NBDClientConnection *conn)
@@ -2230,7 +2233,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }

-    nbd_init_connect_thread(s);
+    s->conn = nbd_client_connection_new(s->saddr);

     /*
      * establish TCP connection, return error if it fails
-- 
2.31.1

[PULL 18/34] block/nbd: introduce nbd_client_connection_release()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

This is a last step of creating bs-independent nbd connection
interface. With next commit we can finally move it to separate file.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-17-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 45 +++++++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index e7261aeaef7b..fa6e5e85bd6f 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -127,7 +127,7 @@ typedef struct BDRVNBDState {
     NBDClientConnection *conn;
 } BDRVNBDState;

-static void nbd_free_connect_thread(NBDClientConnection *conn);
+static void nbd_client_connection_release(NBDClientConnection *conn);
 static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
                                     Error **errp);
 static coroutine_fn QIOChannelSocket *
@@ -139,22 +139,9 @@ static void nbd_yank(void *opaque);
 static void nbd_clear_bdrvstate(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
-    NBDClientConnection *conn = s->conn;
-    bool do_free = false;

-    qemu_mutex_lock(&conn->mutex);
-    assert(!conn->detached);
-    if (conn->running) {
-        conn->detached = true;
-    } else {
-        do_free = true;
-    }
-    qemu_mutex_unlock(&conn->mutex);
-
-    /* the runaway thread will clean up itself */
-    if (do_free) {
-        nbd_free_connect_thread(conn);
-    }
+    nbd_client_connection_release(s->conn);
+    s->conn = NULL;

     yank_unregister_instance(BLOCKDEV_YANK_INSTANCE(bs->node_name));

@@ -372,7 +359,7 @@ nbd_client_connection_new(const SocketAddress *saddr)
     return conn;
 }

-static void nbd_free_connect_thread(NBDClientConnection *conn)
+static void nbd_client_connection_do_free(NBDClientConnection *conn)
 {
     if (conn->sioc) {
         qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
@@ -414,12 +401,34 @@ static void *connect_thread_func(void *opaque)
     qemu_mutex_unlock(&conn->mutex);

     if (do_free) {
-        nbd_free_connect_thread(conn);
+        nbd_client_connection_do_free(conn);
     }

     return NULL;
 }

+static void nbd_client_connection_release(NBDClientConnection *conn)
+{
+    bool do_free = false;
+
+    if (!conn) {
+        return;
+    }
+
+    qemu_mutex_lock(&conn->mutex);
+    assert(!conn->detached);
+    if (conn->running) {
+        conn->detached = true;
+    } else {
+        do_free = true;
+    }
+    qemu_mutex_unlock(&conn->mutex);
+
+    if (do_free) {
+        nbd_client_connection_do_free(conn);
+    }
+}
+
 /*
  * Get a new connection in context of @conn:
  *   if the thread is running, wait for completion
-- 
2.31.1

[PULL 19/34] nbd: move connection code from block/nbd to nbd/client-connection

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We now have bs-independent connection API, which consists of four
functions:

  nbd_client_connection_new()
  nbd_client_connection_release()
  nbd_co_establish_connection()
  nbd_co_establish_connection_cancel()

Move them to a separate file together with NBDClientConnection
structure which becomes private to the new API.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-18-vsementsov@virtuozzo.com>
[eblake: comment tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/nbd.h     |  11 ++
 block/nbd.c             | 207 -----------------------------------
 nbd/client-connection.c | 232 ++++++++++++++++++++++++++++++++++++++++
 nbd/meson.build         |   1 +
 4 files changed, 244 insertions(+), 207 deletions(-)
 create mode 100644 nbd/client-connection.c

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 5f34d23bb037..57381be76fc5 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -406,4 +406,15 @@ const char *nbd_info_lookup(uint16_t info);
 const char *nbd_cmd_lookup(uint16_t info);
 const char *nbd_err_lookup(int err);

+/* nbd/client-connection.c */
+typedef struct NBDClientConnection NBDClientConnection;
+
+NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr);
+void nbd_client_connection_release(NBDClientConnection *conn);
+
+QIOChannelSocket *coroutine_fn
+nbd_co_establish_connection(NBDClientConnection *conn, Error **errp);
+
+void coroutine_fn nbd_co_establish_connection_cancel(NBDClientConnection *conn);
+
 #endif
diff --git a/block/nbd.c b/block/nbd.c
index fa6e5e85bd6f..26914509f153 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -66,33 +66,6 @@ typedef enum NBDClientState {
     NBD_CLIENT_QUIT
 } NBDClientState;

-typedef struct NBDClientConnection {
-    /* Initialization constants */
-    SocketAddress *saddr; /* address to connect to */
-
-    QemuMutex mutex;
-
-    /*
-     * @sioc and @err represent a connection attempt.  While running
-     * is true, they are only used by the connection thread, and mutex
-     * locking is not needed.  Once the thread finishes,
-     * nbd_co_establish_connection then steals these pointers while
-     * under the mutex.
-     */
-    QIOChannelSocket *sioc;
-    Error *err;
-
-    /* All further fields are accessed only under mutex */
-    bool running; /* thread is running now */
-    bool detached; /* thread is detached and should cleanup the state */
-
-    /*
-     * wait_co: if non-NULL, which coroutine to wake in
-     * nbd_co_establish_connection() after yield()
-     */
-    Coroutine *wait_co;
-} NBDClientConnection;
-
 typedef struct BDRVNBDState {
     QIOChannelSocket *sioc; /* The master data channel */
     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
@@ -127,12 +100,8 @@ typedef struct BDRVNBDState {
     NBDClientConnection *conn;
 } BDRVNBDState;

-static void nbd_client_connection_release(NBDClientConnection *conn);
 static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
                                     Error **errp);
-static coroutine_fn QIOChannelSocket *
-nbd_co_establish_connection(NBDClientConnection *conn, Error **errp);
-static void nbd_co_establish_connection_cancel(NBDClientConnection *conn);
 static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
 static void nbd_yank(void *opaque);

@@ -345,182 +314,6 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)
     return qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTING_WAIT;
 }

-static NBDClientConnection *
-nbd_client_connection_new(const SocketAddress *saddr)
-{
-    NBDClientConnection *conn = g_new(NBDClientConnection, 1);
-
-    *conn = (NBDClientConnection) {
-        .saddr = QAPI_CLONE(SocketAddress, saddr),
-    };
-
-    qemu_mutex_init(&conn->mutex);
-
-    return conn;
-}
-
-static void nbd_client_connection_do_free(NBDClientConnection *conn)
-{
-    if (conn->sioc) {
-        qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
-        object_unref(OBJECT(conn->sioc));
-    }
-    error_free(conn->err);
-    qapi_free_SocketAddress(conn->saddr);
-    g_free(conn);
-}
-
-static void *connect_thread_func(void *opaque)
-{
-    NBDClientConnection *conn = opaque;
-    int ret;
-    bool do_free;
-
-    conn->sioc = qio_channel_socket_new();
-
-    error_free(conn->err);
-    conn->err = NULL;
-    ret = qio_channel_socket_connect_sync(conn->sioc, conn->saddr, &conn->err);
-    if (ret < 0) {
-        object_unref(OBJECT(conn->sioc));
-        conn->sioc = NULL;
-    }
-
-    qio_channel_set_delay(QIO_CHANNEL(conn->sioc), false);
-
-    qemu_mutex_lock(&conn->mutex);
-
-    assert(conn->running);
-    conn->running = false;
-    if (conn->wait_co) {
-        aio_co_wake(conn->wait_co);
-        conn->wait_co = NULL;
-    }
-    do_free = conn->detached;
-
-    qemu_mutex_unlock(&conn->mutex);
-
-    if (do_free) {
-        nbd_client_connection_do_free(conn);
-    }
-
-    return NULL;
-}
-
-static void nbd_client_connection_release(NBDClientConnection *conn)
-{
-    bool do_free = false;
-
-    if (!conn) {
-        return;
-    }
-
-    qemu_mutex_lock(&conn->mutex);
-    assert(!conn->detached);
-    if (conn->running) {
-        conn->detached = true;
-    } else {
-        do_free = true;
-    }
-    qemu_mutex_unlock(&conn->mutex);
-
-    if (do_free) {
-        nbd_client_connection_do_free(conn);
-    }
-}
-
-/*
- * Get a new connection in context of @conn:
- *   if the thread is running, wait for completion
- *   if the thread already succeeded in the background, and user didn't get the
- *     result, just return it now
- *   otherwise the thread is not running, so start a thread and wait for
- *     completion
- */
-static coroutine_fn QIOChannelSocket *
-nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
-{
-    QIOChannelSocket *sioc = NULL;
-    QemuThread thread;
-
-    qemu_mutex_lock(&conn->mutex);
-
-    /*
-     * Don't call nbd_co_establish_connection() in several coroutines in
-     * parallel. Only one call at once is supported.
-     */
-    assert(!conn->wait_co);
-
-    if (!conn->running) {
-        if (conn->sioc) {
-            /* Previous attempt finally succeeded in background */
-            sioc = g_steal_pointer(&conn->sioc);
-            qemu_mutex_unlock(&conn->mutex);
-
-            return sioc;
-        }
-
-        conn->running = true;
-        error_free(conn->err);
-        conn->err = NULL;
-        qemu_thread_create(&thread, "nbd-connect",
-                           connect_thread_func, conn, QEMU_THREAD_DETACHED);
-    }
-
-    conn->wait_co = qemu_coroutine_self();
-
-    qemu_mutex_unlock(&conn->mutex);
-
-    /*
-     * We are going to wait for connect-thread finish, but
-     * nbd_co_establish_connection_cancel() can interrupt.
-     */
-    qemu_coroutine_yield();
-
-    qemu_mutex_lock(&conn->mutex);
-
-    if (conn->running) {
-        /*
-         * The connection attempt was canceled and the coroutine resumed
-         * before the connection thread finished its job.  Report the
-         * attempt as failed, but leave the connection thread running,
-         * to reuse it for the next connection attempt.
-         */
-        error_setg(errp, "Connection attempt cancelled by other operation");
-    } else {
-        error_propagate(errp, conn->err);
-        conn->err = NULL;
-        sioc = g_steal_pointer(&conn->sioc);
-    }
-
-    qemu_mutex_unlock(&conn->mutex);
-
-    return sioc;
-}
-
-/*
- * nbd_co_establish_connection_cancel
- * Cancel nbd_co_establish_connection() asynchronously.
- *
- * Note that this function neither directly stops the thread nor closes the
- * socket, but rather safely wakes nbd_co_establish_connection() which is
- * sleeping in yield()
- */
-static void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
-{
-    Coroutine *wait_co;
-
-    qemu_mutex_lock(&conn->mutex);
-
-    wait_co = g_steal_pointer(&conn->wait_co);
-
-    qemu_mutex_unlock(&conn->mutex);
-
-    if (wait_co) {
-        aio_co_wake(wait_co);
-    }
-}
-
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
diff --git a/nbd/client-connection.c b/nbd/client-connection.c
new file mode 100644
index 000000000000..f3b270d38cc8
--- /dev/null
+++ b/nbd/client-connection.c
@@ -0,0 +1,232 @@
+/*
+ * QEMU Block driver for  NBD
+ *
+ * Copyright (c) 2021 Virtuozzo International GmbH.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+
+#include "block/nbd.h"
+
+#include "qapi/qapi-visit-sockets.h"
+#include "qapi/clone-visitor.h"
+
+struct NBDClientConnection {
+    /* Initialization constants */
+    SocketAddress *saddr; /* address to connect to */
+
+    QemuMutex mutex;
+
+    /*
+     * @sioc and @err represent a connection attempt.  While running
+     * is true, they are only used by the connection thread, and mutex
+     * locking is not needed.  Once the thread finishes,
+     * nbd_co_establish_connection then steals these pointers while
+     * under the mutex.
+     */
+    QIOChannelSocket *sioc;
+    Error *err;
+
+    /* All further fields are accessed only under mutex */
+    bool running; /* thread is running now */
+    bool detached; /* thread is detached and should cleanup the state */
+
+    /*
+     * wait_co: if non-NULL, which coroutine to wake in
+     * nbd_co_establish_connection() after yield()
+     */
+    Coroutine *wait_co;
+};
+
+NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr)
+{
+    NBDClientConnection *conn = g_new(NBDClientConnection, 1);
+
+    *conn = (NBDClientConnection) {
+        .saddr = QAPI_CLONE(SocketAddress, saddr),
+    };
+
+    qemu_mutex_init(&conn->mutex);
+
+    return conn;
+}
+
+static void nbd_client_connection_do_free(NBDClientConnection *conn)
+{
+    if (conn->sioc) {
+        qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
+        object_unref(OBJECT(conn->sioc));
+    }
+    error_free(conn->err);
+    qapi_free_SocketAddress(conn->saddr);
+    g_free(conn);
+}
+
+static void *connect_thread_func(void *opaque)
+{
+    NBDClientConnection *conn = opaque;
+    int ret;
+    bool do_free;
+
+    conn->sioc = qio_channel_socket_new();
+
+    error_free(conn->err);
+    conn->err = NULL;
+    ret = qio_channel_socket_connect_sync(conn->sioc, conn->saddr, &conn->err);
+    if (ret < 0) {
+        object_unref(OBJECT(conn->sioc));
+        conn->sioc = NULL;
+    }
+
+    qio_channel_set_delay(QIO_CHANNEL(conn->sioc), false);
+
+    qemu_mutex_lock(&conn->mutex);
+
+    assert(conn->running);
+    conn->running = false;
+    if (conn->wait_co) {
+        aio_co_wake(conn->wait_co);
+        conn->wait_co = NULL;
+    }
+    do_free = conn->detached;
+
+    qemu_mutex_unlock(&conn->mutex);
+
+    if (do_free) {
+        nbd_client_connection_do_free(conn);
+    }
+
+    return NULL;
+}
+
+void nbd_client_connection_release(NBDClientConnection *conn)
+{
+    bool do_free = false;
+
+    if (!conn) {
+        return;
+    }
+
+    qemu_mutex_lock(&conn->mutex);
+    assert(!conn->detached);
+    if (conn->running) {
+        conn->detached = true;
+    } else {
+        do_free = true;
+    }
+    qemu_mutex_unlock(&conn->mutex);
+
+    if (do_free) {
+        nbd_client_connection_do_free(conn);
+    }
+}
+
+/*
+ * Get a new connection in context of @conn:
+ *   if the thread is running, wait for completion
+ *   if the thread already succeeded in the background, and user didn't get the
+ *     result, just return it now
+ *   otherwise the thread is not running, so start a thread and wait for
+ *     completion
+ */
+QIOChannelSocket *coroutine_fn
+nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
+{
+    QIOChannelSocket *sioc = NULL;
+    QemuThread thread;
+
+    qemu_mutex_lock(&conn->mutex);
+
+    /*
+     * Don't call nbd_co_establish_connection() in several coroutines in
+     * parallel. Only one call at once is supported.
+     */
+    assert(!conn->wait_co);
+
+    if (!conn->running) {
+        if (conn->sioc) {
+            /* Previous attempt finally succeeded in background */
+            sioc = g_steal_pointer(&conn->sioc);
+            qemu_mutex_unlock(&conn->mutex);
+
+            return sioc;
+        }
+
+        conn->running = true;
+        error_free(conn->err);
+        conn->err = NULL;
+        qemu_thread_create(&thread, "nbd-connect",
+                           connect_thread_func, conn, QEMU_THREAD_DETACHED);
+    }
+
+    conn->wait_co = qemu_coroutine_self();
+
+    qemu_mutex_unlock(&conn->mutex);
+
+    /*
+     * We are going to wait for connect-thread finish, but
+     * nbd_co_establish_connection_cancel() can interrupt.
+     */
+    qemu_coroutine_yield();
+
+    qemu_mutex_lock(&conn->mutex);
+
+    if (conn->running) {
+        /*
+         * The connection attempt was canceled and the coroutine resumed
+         * before the connection thread finished its job.  Report the
+         * attempt as failed, but leave the connection thread running,
+         * to reuse it for the next connection attempt.
+         */
+        error_setg(errp, "Connection attempt cancelled by other operation");
+    } else {
+        error_propagate(errp, conn->err);
+        conn->err = NULL;
+        sioc = g_steal_pointer(&conn->sioc);
+    }
+
+    qemu_mutex_unlock(&conn->mutex);
+
+    return sioc;
+}
+
+/*
+ * nbd_co_establish_connection_cancel
+ * Cancel nbd_co_establish_connection() asynchronously.
+ *
+ * Note that this function neither directly stops the thread nor closes the
+ * socket, but rather safely wakes nbd_co_establish_connection() which is
+ * sleeping in yield()
+ */
+void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
+{
+    Coroutine *wait_co;
+
+    qemu_mutex_lock(&conn->mutex);
+
+    wait_co = g_steal_pointer(&conn->wait_co);
+
+    qemu_mutex_unlock(&conn->mutex);
+
+    if (wait_co) {
+        aio_co_wake(wait_co);
+    }
+}
diff --git a/nbd/meson.build b/nbd/meson.build
index 2baaa3694801..b26d70565ebb 100644
--- a/nbd/meson.build
+++ b/nbd/meson.build
@@ -1,5 +1,6 @@
 block_ss.add(files(
   'client.c',
+  'client-connection.c',
   'common.c',
 ))
 blockdev_ss.add(files(
-- 
2.31.1

[PULL 20/34] nbd/client-connection: use QEMU_LOCK_GUARD

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We don't update connect_thread_func() to use QEMU_LOCK_GUARD, as it
will get more complex critical sections logic in further commit, where
QEMU_LOCK_GUARD doesn't help.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-19-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 nbd/client-connection.c | 95 +++++++++++++++++++----------------------
 1 file changed, 43 insertions(+), 52 deletions(-)

diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index f3b270d38cc8..eb5cae2eaea4 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -125,14 +125,14 @@ void nbd_client_connection_release(NBDClientConnection *conn)
         return;
     }

-    qemu_mutex_lock(&conn->mutex);
-    assert(!conn->detached);
-    if (conn->running) {
-        conn->detached = true;
-    } else {
-        do_free = true;
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        assert(!conn->detached);
+        if (conn->running) {
+            conn->detached = true;
+        } else {
+            do_free = true;
+        }
     }
-    qemu_mutex_unlock(&conn->mutex);

     if (do_free) {
         nbd_client_connection_do_free(conn);
@@ -150,62 +150,55 @@ void nbd_client_connection_release(NBDClientConnection *conn)
 QIOChannelSocket *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
 {
-    QIOChannelSocket *sioc = NULL;
     QemuThread thread;

-    qemu_mutex_lock(&conn->mutex);
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        /*
+         * Don't call nbd_co_establish_connection() in several coroutines in
+         * parallel. Only one call at once is supported.
+         */
+        assert(!conn->wait_co);

-    /*
-     * Don't call nbd_co_establish_connection() in several coroutines in
-     * parallel. Only one call at once is supported.
-     */
-    assert(!conn->wait_co);
+        if (!conn->running) {
+            if (conn->sioc) {
+                /* Previous attempt finally succeeded in background */
+                return g_steal_pointer(&conn->sioc);
+            }

-    if (!conn->running) {
-        if (conn->sioc) {
-            /* Previous attempt finally succeeded in background */
-            sioc = g_steal_pointer(&conn->sioc);
-            qemu_mutex_unlock(&conn->mutex);
-
-            return sioc;
+            conn->running = true;
+            error_free(conn->err);
+            conn->err = NULL;
+            qemu_thread_create(&thread, "nbd-connect",
+                               connect_thread_func, conn, QEMU_THREAD_DETACHED);
         }

-        conn->running = true;
-        error_free(conn->err);
-        conn->err = NULL;
-        qemu_thread_create(&thread, "nbd-connect",
-                           connect_thread_func, conn, QEMU_THREAD_DETACHED);
+        conn->wait_co = qemu_coroutine_self();
     }

-    conn->wait_co = qemu_coroutine_self();
-
-    qemu_mutex_unlock(&conn->mutex);
-
     /*
      * We are going to wait for connect-thread finish, but
      * nbd_co_establish_connection_cancel() can interrupt.
      */
     qemu_coroutine_yield();

-    qemu_mutex_lock(&conn->mutex);
-
-    if (conn->running) {
-        /*
-         * The connection attempt was canceled and the coroutine resumed
-         * before the connection thread finished its job.  Report the
-         * attempt as failed, but leave the connection thread running,
-         * to reuse it for the next connection attempt.
-         */
-        error_setg(errp, "Connection attempt cancelled by other operation");
-    } else {
-        error_propagate(errp, conn->err);
-        conn->err = NULL;
-        sioc = g_steal_pointer(&conn->sioc);
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        if (conn->running) {
+            /*
+             * The connection attempt was canceled and the coroutine resumed
+             * before the connection thread finished its job.  Report the
+             * attempt as failed, but leave the connection thread running,
+             * to reuse it for the next connection attempt.
+             */
+            error_setg(errp, "Connection attempt cancelled by other operation");
+            return NULL;
+        } else {
+            error_propagate(errp, conn->err);
+            conn->err = NULL;
+            return g_steal_pointer(&conn->sioc);
+        }
     }

-    qemu_mutex_unlock(&conn->mutex);
-
-    return sioc;
+    abort(); /* unreachable */
 }

 /*
@@ -220,11 +213,9 @@ void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
 {
     Coroutine *wait_co;

-    qemu_mutex_lock(&conn->mutex);
-
-    wait_co = g_steal_pointer(&conn->wait_co);
-
-    qemu_mutex_unlock(&conn->mutex);
+    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
+        wait_co = g_steal_pointer(&conn->wait_co);
+    }

     if (wait_co) {
         aio_co_wake(wait_co);
-- 
2.31.1

[PULL 21/34] nbd/client-connection: add possibility of negotiation

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Add arguments and logic to support nbd negotiation in the same thread
after successful connection.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-20-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/nbd.h     |   9 +++-
 block/nbd.c             |   4 +-
 nbd/client-connection.c | 105 ++++++++++++++++++++++++++++++++++++++--
 3 files changed, 109 insertions(+), 9 deletions(-)

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 57381be76fc5..5d86e6a393ff 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -409,11 +409,16 @@ const char *nbd_err_lookup(int err);
 /* nbd/client-connection.c */
 typedef struct NBDClientConnection NBDClientConnection;

-NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr);
+NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
+                                               bool do_negotiation,
+                                               const char *export_name,
+                                               const char *x_dirty_bitmap,
+                                               QCryptoTLSCreds *tlscreds);
 void nbd_client_connection_release(NBDClientConnection *conn);

 QIOChannelSocket *coroutine_fn
-nbd_co_establish_connection(NBDClientConnection *conn, Error **errp);
+nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
+                            QIOChannel **ioc, Error **errp);

 void coroutine_fn nbd_co_establish_connection_cancel(NBDClientConnection *conn);

diff --git a/block/nbd.c b/block/nbd.c
index 26914509f153..df9d241313f4 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -357,7 +357,7 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    s->sioc = nbd_co_establish_connection(s->conn, NULL);
+    s->sioc = nbd_co_establish_connection(s->conn, NULL, NULL, NULL);
     if (!s->sioc) {
         ret = -ECONNREFUSED;
         goto out;
@@ -2035,7 +2035,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }

-    s->conn = nbd_client_connection_new(s->saddr);
+    s->conn = nbd_client_connection_new(s->saddr, false, NULL, NULL, NULL);

     /*
      * establish TCP connection, return error if it fails
diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index eb5cae2eaea4..4ed37cd73fa1 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -30,8 +30,11 @@
 #include "qapi/clone-visitor.h"

 struct NBDClientConnection {
-    /* Initialization constants */
+    /* Initialization constants, never change */
     SocketAddress *saddr; /* address to connect to */
+    QCryptoTLSCreds *tlscreds;
+    NBDExportInfo initial_info;
+    bool do_negotiation;

     QemuMutex mutex;

@@ -42,7 +45,9 @@ struct NBDClientConnection {
      * nbd_co_establish_connection then steals these pointers while
      * under the mutex.
      */
+    NBDExportInfo updated_info;
     QIOChannelSocket *sioc;
+    QIOChannel *ioc;
     Error *err;

     /* All further fields are accessed only under mutex */
@@ -56,12 +61,25 @@ struct NBDClientConnection {
     Coroutine *wait_co;
 };

-NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr)
+NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
+                                               bool do_negotiation,
+                                               const char *export_name,
+                                               const char *x_dirty_bitmap,
+                                               QCryptoTLSCreds *tlscreds)
 {
     NBDClientConnection *conn = g_new(NBDClientConnection, 1);

+    object_ref(OBJECT(tlscreds));
     *conn = (NBDClientConnection) {
         .saddr = QAPI_CLONE(SocketAddress, saddr),
+        .tlscreds = tlscreds,
+        .do_negotiation = do_negotiation,
+
+        .initial_info.request_sizes = true,
+        .initial_info.structured_reply = true,
+        .initial_info.base_allocation = true,
+        .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
+        .initial_info.name = g_strdup(export_name ?: "")
     };

     qemu_mutex_init(&conn->mutex);
@@ -77,9 +95,61 @@ static void nbd_client_connection_do_free(NBDClientConnection *conn)
     }
     error_free(conn->err);
     qapi_free_SocketAddress(conn->saddr);
+    object_unref(OBJECT(conn->tlscreds));
+    g_free(conn->initial_info.x_dirty_bitmap);
+    g_free(conn->initial_info.name);
     g_free(conn);
 }

+/*
+ * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
+ * are given @outioc is returned. @outioc is provided only on success.  The call
+ * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
+ */
+static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
+                       NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
+                       QIOChannel **outioc, Error **errp)
+{
+    int ret;
+
+    if (outioc) {
+        *outioc = NULL;
+    }
+
+    ret = qio_channel_socket_connect_sync(sioc, addr, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    qio_channel_set_delay(QIO_CHANNEL(sioc), false);
+
+    if (!info) {
+        return 0;
+    }
+
+    ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc), tlscreds,
+                                tlscreds ? addr->u.inet.host : NULL,
+                                outioc, info, errp);
+    if (ret < 0) {
+        /*
+         * nbd_receive_negotiate() may setup tls ioc and return it even on
+         * failure path. In this case we should use it instead of original
+         * channel.
+         */
+        if (outioc && *outioc) {
+            qio_channel_close(QIO_CHANNEL(*outioc), NULL);
+            object_unref(OBJECT(*outioc));
+            *outioc = NULL;
+        } else {
+            qio_channel_close(QIO_CHANNEL(sioc), NULL);
+        }
+
+        return ret;
+    }
+
+    return 0;
+}
+
 static void *connect_thread_func(void *opaque)
 {
     NBDClientConnection *conn = opaque;
@@ -90,13 +160,18 @@ static void *connect_thread_func(void *opaque)

     error_free(conn->err);
     conn->err = NULL;
-    ret = qio_channel_socket_connect_sync(conn->sioc, conn->saddr, &conn->err);
+    conn->updated_info = conn->initial_info;
+
+    ret = nbd_connect(conn->sioc, conn->saddr,
+                      conn->do_negotiation ? &conn->updated_info : NULL,
+                      conn->tlscreds, &conn->ioc, &conn->err);
     if (ret < 0) {
         object_unref(OBJECT(conn->sioc));
         conn->sioc = NULL;
     }

-    qio_channel_set_delay(QIO_CHANNEL(conn->sioc), false);
+    conn->updated_info.x_dirty_bitmap = NULL;
+    conn->updated_info.name = NULL;

     qemu_mutex_lock(&conn->mutex);

@@ -146,12 +221,24 @@ void nbd_client_connection_release(NBDClientConnection *conn)
  *     result, just return it now
  *   otherwise the thread is not running, so start a thread and wait for
  *     completion
+ *
+ * If @info is not NULL, also do nbd-negotiation after successful connection.
+ * In this case info is used only as out parameter, and is fully initialized by
+ * nbd_co_establish_connection(). "IN" fields of info as well as related only to
+ * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
+ * include/block/nbd.h).
  */
 QIOChannelSocket *coroutine_fn
-nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
+nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
+                            QIOChannel **ioc, Error **errp)
 {
     QemuThread thread;

+    if (conn->do_negotiation) {
+        assert(info);
+        assert(ioc);
+    }
+
     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
         /*
          * Don't call nbd_co_establish_connection() in several coroutines in
@@ -162,6 +249,10 @@ nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
         if (!conn->running) {
             if (conn->sioc) {
                 /* Previous attempt finally succeeded in background */
+                if (conn->do_negotiation) {
+                    *ioc = g_steal_pointer(&conn->ioc);
+                    memcpy(info, &conn->updated_info, sizeof(*info));
+                }
                 return g_steal_pointer(&conn->sioc);
             }

@@ -194,6 +285,10 @@ nbd_co_establish_connection(NBDClientConnection *conn, Error **errp)
         } else {
             error_propagate(errp, conn->err);
             conn->err = NULL;
+            if (conn->sioc && conn->do_negotiation) {
+                *ioc = g_steal_pointer(&conn->ioc);
+                memcpy(info, &conn->updated_info, sizeof(*info));
+            }
             return g_steal_pointer(&conn->sioc);
         }
     }
-- 
2.31.1

[PULL 22/34] nbd/client-connection: implement connection retry

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Add an option for a thread to retry connecting until it succeeds. We'll
use nbd/client-connection both for reconnect and for initial connection
in nbd_open(), so we need a possibility to use same NBDClientConnection
instance to connect once in nbd_open() and then use retry semantics for
reconnect.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-21-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/nbd.h     |  2 ++
 nbd/client-connection.c | 56 +++++++++++++++++++++++++++++++----------
 2 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 5d86e6a393ff..5bb54d831c8a 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -409,6 +409,8 @@ const char *nbd_err_lookup(int err);
 /* nbd/client-connection.c */
 typedef struct NBDClientConnection NBDClientConnection;

+void nbd_client_connection_enable_retry(NBDClientConnection *conn);
+
 NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
                                                bool do_negotiation,
                                                const char *export_name,
diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 4ed37cd73fa1..032b38ed3e9b 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -35,6 +35,7 @@ struct NBDClientConnection {
     QCryptoTLSCreds *tlscreds;
     NBDExportInfo initial_info;
     bool do_negotiation;
+    bool do_retry;

     QemuMutex mutex;

@@ -61,6 +62,15 @@ struct NBDClientConnection {
     Coroutine *wait_co;
 };

+/*
+ * The function isn't protected by any mutex, only call it when the client
+ * connection attempt has not yet started.
+ */
+void nbd_client_connection_enable_retry(NBDClientConnection *conn)
+{
+    conn->do_retry = true;
+}
+
 NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
                                                bool do_negotiation,
                                                const char *export_name,
@@ -155,24 +165,44 @@ static void *connect_thread_func(void *opaque)
     NBDClientConnection *conn = opaque;
     int ret;
     bool do_free;
+    uint64_t timeout = 1;
+    uint64_t max_timeout = 16;

-    conn->sioc = qio_channel_socket_new();
+    while (true) {
+        conn->sioc = qio_channel_socket_new();

-    error_free(conn->err);
-    conn->err = NULL;
-    conn->updated_info = conn->initial_info;
+        error_free(conn->err);
+        conn->err = NULL;
+        conn->updated_info = conn->initial_info;

-    ret = nbd_connect(conn->sioc, conn->saddr,
-                      conn->do_negotiation ? &conn->updated_info : NULL,
-                      conn->tlscreds, &conn->ioc, &conn->err);
-    if (ret < 0) {
-        object_unref(OBJECT(conn->sioc));
-        conn->sioc = NULL;
+        ret = nbd_connect(conn->sioc, conn->saddr,
+                          conn->do_negotiation ? &conn->updated_info : NULL,
+                          conn->tlscreds, &conn->ioc, &conn->err);
+
+        /*
+         * conn->updated_info will finally be returned to the user. Clear the
+         * pointers to our internally allocated strings, which are IN parameters
+         * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
+         * shoudn't be interested in these fields.
+         */
+        conn->updated_info.x_dirty_bitmap = NULL;
+        conn->updated_info.name = NULL;
+
+        if (ret < 0) {
+            object_unref(OBJECT(conn->sioc));
+            conn->sioc = NULL;
+            if (conn->do_retry) {
+                sleep(timeout);
+                if (timeout < max_timeout) {
+                    timeout *= 2;
+                }
+                continue;
+            }
+        }
+
+        break;
     }

-    conn->updated_info.x_dirty_bitmap = NULL;
-    conn->updated_info.name = NULL;
-
     qemu_mutex_lock(&conn->mutex);

     assert(conn->running);
-- 
2.31.1

[PULL 23/34] nbd/client-connection: shutdown connection on release

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Now, when a thread can do negotiation and retry, it may run relatively
long. We need a mechanism to stop it, when the user is not interested
in a result any more. So, on nbd_client_connection_release() let's
shutdown the socket, and do not retry connection if thread is detached.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-22-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 nbd/client-connection.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 032b38ed3e9b..883f9cf158cb 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -168,9 +168,13 @@ static void *connect_thread_func(void *opaque)
     uint64_t timeout = 1;
     uint64_t max_timeout = 16;

-    while (true) {
+    qemu_mutex_lock(&conn->mutex);
+    while (!conn->detached) {
+        assert(!conn->sioc);
         conn->sioc = qio_channel_socket_new();

+        qemu_mutex_unlock(&conn->mutex);
+
         error_free(conn->err);
         conn->err = NULL;
         conn->updated_info = conn->initial_info;
@@ -188,14 +192,20 @@ static void *connect_thread_func(void *opaque)
         conn->updated_info.x_dirty_bitmap = NULL;
         conn->updated_info.name = NULL;

+        qemu_mutex_lock(&conn->mutex);
+
         if (ret < 0) {
             object_unref(OBJECT(conn->sioc));
             conn->sioc = NULL;
-            if (conn->do_retry) {
+            if (conn->do_retry && !conn->detached) {
+                qemu_mutex_unlock(&conn->mutex);
+
                 sleep(timeout);
                 if (timeout < max_timeout) {
                     timeout *= 2;
                 }
+
+                qemu_mutex_lock(&conn->mutex);
                 continue;
             }
         }
@@ -203,7 +213,7 @@ static void *connect_thread_func(void *opaque)
         break;
     }

-    qemu_mutex_lock(&conn->mutex);
+    /* mutex is locked */

     assert(conn->running);
     conn->running = false;
@@ -237,6 +247,10 @@ void nbd_client_connection_release(NBDClientConnection *conn)
         } else {
             do_free = true;
         }
+        if (conn->sioc) {
+            qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
+                                 QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
+        }
     }

     if (do_free) {
-- 
2.31.1

[PULL 24/34] block/nbd: split nbd_handle_updated_info out of nbd_client_handshake()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

To be reused in the following patch.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-23-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 112 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 64 insertions(+), 48 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index df9d241313f4..240c6e1b3d72 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -314,6 +314,51 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)
     return qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTING_WAIT;
 }

+/*
+ * Update @bs with information learned during a completed negotiation process.
+ * Return failure if the server's advertised options are incompatible with the
+ * client's needs.
+ */
+static int nbd_handle_updated_info(BlockDriverState *bs, Error **errp)
+{
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    int ret;
+
+    if (s->x_dirty_bitmap) {
+        if (!s->info.base_allocation) {
+            error_setg(errp, "requested x-dirty-bitmap %s not found",
+                       s->x_dirty_bitmap);
+            return -EINVAL;
+        }
+        if (strcmp(s->x_dirty_bitmap, "qemu:allocation-depth") == 0) {
+            s->alloc_depth = true;
+        }
+    }
+
+    if (s->info.flags & NBD_FLAG_READ_ONLY) {
+        ret = bdrv_apply_auto_read_only(bs, "NBD export is read-only", errp);
+        if (ret < 0) {
+            return ret;
+        }
+    }
+
+    if (s->info.flags & NBD_FLAG_SEND_FUA) {
+        bs->supported_write_flags = BDRV_REQ_FUA;
+        bs->supported_zero_flags |= BDRV_REQ_FUA;
+    }
+
+    if (s->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
+        bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
+        if (s->info.flags & NBD_FLAG_SEND_FAST_ZERO) {
+            bs->supported_zero_flags |= BDRV_REQ_NO_FALLBACK;
+        }
+    }
+
+    trace_nbd_client_handshake_success(s->export);
+
+    return 0;
+}
+
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
@@ -1575,32 +1620,25 @@ static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
         s->sioc = NULL;
         return ret;
     }
-    if (s->x_dirty_bitmap) {
-        if (!s->info.base_allocation) {
-            error_setg(errp, "requested x-dirty-bitmap %s not found",
-                       s->x_dirty_bitmap);
-            ret = -EINVAL;
-            goto fail;
-        }
-        if (strcmp(s->x_dirty_bitmap, "qemu:allocation-depth") == 0) {
-            s->alloc_depth = true;
-        }
-    }
-    if (s->info.flags & NBD_FLAG_READ_ONLY) {
-        ret = bdrv_apply_auto_read_only(bs, "NBD export is read-only", errp);
-        if (ret < 0) {
-            goto fail;
-        }
-    }
-    if (s->info.flags & NBD_FLAG_SEND_FUA) {
-        bs->supported_write_flags = BDRV_REQ_FUA;
-        bs->supported_zero_flags |= BDRV_REQ_FUA;
-    }
-    if (s->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
-        bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
-        if (s->info.flags & NBD_FLAG_SEND_FAST_ZERO) {
-            bs->supported_zero_flags |= BDRV_REQ_NO_FALLBACK;
-        }
+
+    ret = nbd_handle_updated_info(bs, errp);
+    if (ret < 0) {
+        /*
+         * We have connected, but must fail for other reasons.
+         * Send NBD_CMD_DISC as a courtesy to the server.
+         */
+        NBDRequest request = { .type = NBD_CMD_DISC };
+
+        nbd_send_request(s->ioc ?: QIO_CHANNEL(s->sioc), &request);
+
+        yank_unregister_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
+                                 nbd_yank, bs);
+        object_unref(OBJECT(s->sioc));
+        s->sioc = NULL;
+        object_unref(OBJECT(s->ioc));
+        s->ioc = NULL;
+
+        return ret;
     }

     if (!s->ioc) {
@@ -1608,29 +1646,7 @@ static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
         object_ref(OBJECT(s->ioc));
     }

-    trace_nbd_client_handshake_success(s->export);
-
     return 0;
-
- fail:
-    /*
-     * We have connected, but must fail for other reasons.
-     * Send NBD_CMD_DISC as a courtesy to the server.
-     */
-    {
-        NBDRequest request = { .type = NBD_CMD_DISC };
-
-        nbd_send_request(s->ioc ?: QIO_CHANNEL(s->sioc), &request);
-
-        yank_unregister_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
-                                 nbd_yank, bs);
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
-        object_unref(OBJECT(s->ioc));
-        s->ioc = NULL;
-
-        return ret;
-    }
 }

 /*
-- 
2.31.1

[PULL 25/34] block/nbd: use negotiation of NBDClientConnection

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Now that we can opt in to negotiation as part of the client connection
thread, use that to simplify connection_co.  This is another step on
the way to moving all reconnect code into NBDClientConnection.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-24-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 44 ++++++++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 240c6e1b3d72..311471644487 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -362,6 +362,7 @@ static int nbd_handle_updated_info(BlockDriverState *bs, Error **errp)
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
+    AioContext *aio_context = bdrv_get_aio_context(s->bs);

     if (!nbd_client_connecting(s)) {
         return;
@@ -402,30 +403,44 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    s->sioc = nbd_co_establish_connection(s->conn, NULL, NULL, NULL);
+    s->sioc = nbd_co_establish_connection(s->conn, &s->info, &s->ioc, NULL);
     if (!s->sioc) {
         ret = -ECONNREFUSED;
         goto out;
     }

+    qio_channel_set_blocking(QIO_CHANNEL(s->sioc), false, NULL);
+    qio_channel_attach_aio_context(QIO_CHANNEL(s->sioc), aio_context);
+    if (s->ioc) {
+        qio_channel_set_blocking(QIO_CHANNEL(s->ioc), false, NULL);
+        qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), aio_context);
+    } else {
+        s->ioc = QIO_CHANNEL(s->sioc);
+        object_ref(OBJECT(s->ioc));
+    }
+
     yank_register_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name), nbd_yank,
                            s->bs);

-    bdrv_dec_in_flight(s->bs);
+    ret = nbd_handle_updated_info(s->bs, NULL);
+    if (ret < 0) {
+        /*
+         * We have connected, but must fail for other reasons.
+         * Send NBD_CMD_DISC as a courtesy to the server.
+         */
+        NBDRequest request = { .type = NBD_CMD_DISC };

-    ret = nbd_client_handshake(s->bs, NULL);
+        nbd_send_request(s->ioc, &request);

-    if (s->drained) {
-        s->wait_drained_end = true;
-        while (s->drained) {
-            /*
-             * We may be entered once from nbd_client_attach_aio_context_bh
-             * and then from nbd_client_co_drain_end. So here is a loop.
-             */
-            qemu_coroutine_yield();
-        }
+        yank_unregister_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name),
+                                 nbd_yank, s->bs);
+        object_unref(OBJECT(s->sioc));
+        s->sioc = NULL;
+        object_unref(OBJECT(s->ioc));
+        s->ioc = NULL;
+
+        return;
     }
-    bdrv_inc_in_flight(s->bs);

 out:
     if (ret >= 0) {
@@ -2051,7 +2066,8 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }

-    s->conn = nbd_client_connection_new(s->saddr, false, NULL, NULL, NULL);
+    s->conn = nbd_client_connection_new(s->saddr, true, s->export,
+                                        s->x_dirty_bitmap, s->tlscreds);

     /*
      * establish TCP connection, return error if it fails
-- 
2.31.1

[PULL 26/34] block/nbd: don't touch s->sioc in nbd_teardown_connection()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Negotiation during reconnect is now done in a thread, and s->sioc is
not available during negotiation. Negotiation in thread will be
cancelled by nbd_client_connection_release() called from
nbd_clear_bdrvstate().  So, we don't need this code chunk anymore.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-25-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 311471644487..2abcedd464c7 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -280,10 +280,6 @@ static void nbd_teardown_connection(BlockDriverState *bs)
     if (s->ioc) {
         /* finish any pending coroutines */
         qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
-    } else if (s->sioc) {
-        /* abort negotiation */
-        qio_channel_shutdown(QIO_CHANNEL(s->sioc), QIO_CHANNEL_SHUTDOWN_BOTH,
-                             NULL);
     }

     s->state = NBD_CLIENT_QUIT;
-- 
2.31.1

[PULL 27/34] block/nbd: drop BDRVNBDState::sioc

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Currently sioc pointer is used just to pass from socket-connection to
nbd negotiation. Drop the field, and use local variables instead. With
next commit we'll update nbd/client-connection.c to behave
appropriately (return only top-most ioc, not two channels).

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-26-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 98 ++++++++++++++++++++++++++---------------------------
 1 file changed, 48 insertions(+), 50 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 2abcedd464c7..9f193d130bcd 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -67,8 +67,7 @@ typedef enum NBDClientState {
 } NBDClientState;

 typedef struct BDRVNBDState {
-    QIOChannelSocket *sioc; /* The master data channel */
-    QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
+    QIOChannel *ioc; /* The current I/O channel */
     NBDExportInfo info;

     CoMutex send_mutex;
@@ -100,9 +99,11 @@ typedef struct BDRVNBDState {
     NBDClientConnection *conn;
 } BDRVNBDState;

-static int nbd_establish_connection(BlockDriverState *bs, SocketAddress *saddr,
-                                    Error **errp);
-static int nbd_client_handshake(BlockDriverState *bs, Error **errp);
+static QIOChannelSocket *nbd_establish_connection(BlockDriverState *bs,
+                                                  SocketAddress *saddr,
+                                                  Error **errp);
+static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
+                                Error **errp);
 static void nbd_yank(void *opaque);

 static void nbd_clear_bdrvstate(BlockDriverState *bs)
@@ -359,6 +360,7 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
     AioContext *aio_context = bdrv_get_aio_context(s->bs);
+    QIOChannelSocket *sioc;

     if (!nbd_client_connecting(s)) {
         return;
@@ -393,27 +395,26 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         qio_channel_detach_aio_context(QIO_CHANNEL(s->ioc));
         yank_unregister_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name),
                                  nbd_yank, s->bs);
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
         object_unref(OBJECT(s->ioc));
         s->ioc = NULL;
     }

-    s->sioc = nbd_co_establish_connection(s->conn, &s->info, &s->ioc, NULL);
-    if (!s->sioc) {
+    sioc = nbd_co_establish_connection(s->conn, &s->info, &s->ioc, NULL);
+    if (!sioc) {
         ret = -ECONNREFUSED;
         goto out;
     }

-    qio_channel_set_blocking(QIO_CHANNEL(s->sioc), false, NULL);
-    qio_channel_attach_aio_context(QIO_CHANNEL(s->sioc), aio_context);
     if (s->ioc) {
-        qio_channel_set_blocking(QIO_CHANNEL(s->ioc), false, NULL);
-        qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), aio_context);
+        /* sioc is referenced by s->ioc */
+        object_unref(OBJECT(sioc));
     } else {
-        s->ioc = QIO_CHANNEL(s->sioc);
-        object_ref(OBJECT(s->ioc));
+        s->ioc = QIO_CHANNEL(sioc);
     }
+    sioc = NULL;
+
+    qio_channel_set_blocking(QIO_CHANNEL(s->ioc), false, NULL);
+    qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), aio_context);

     yank_register_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name), nbd_yank,
                            s->bs);
@@ -430,8 +431,6 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)

         yank_unregister_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name),
                                  nbd_yank, s->bs);
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
         object_unref(OBJECT(s->ioc));
         s->ioc = NULL;

@@ -566,8 +565,6 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
         qio_channel_detach_aio_context(QIO_CHANNEL(s->ioc));
         yank_unregister_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name),
                                  nbd_yank, s->bs);
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
         object_unref(OBJECT(s->ioc));
         s->ioc = NULL;
     }
@@ -1566,7 +1563,7 @@ static void nbd_yank(void *opaque)
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;

     qatomic_store_release(&s->state, NBD_CLIENT_QUIT);
-    qio_channel_shutdown(QIO_CHANNEL(s->sioc), QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
+    qio_channel_shutdown(QIO_CHANNEL(s->ioc), QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
 }

 static void nbd_client_close(BlockDriverState *bs)
@@ -1581,57 +1578,64 @@ static void nbd_client_close(BlockDriverState *bs)
     nbd_teardown_connection(bs);
 }

-static int nbd_establish_connection(BlockDriverState *bs,
-                                    SocketAddress *saddr,
-                                    Error **errp)
+static QIOChannelSocket *nbd_establish_connection(BlockDriverState *bs,
+                                                  SocketAddress *saddr,
+                                                  Error **errp)
 {
     ERRP_GUARD();
-    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    QIOChannelSocket *sioc;

-    s->sioc = qio_channel_socket_new();
-    qio_channel_set_name(QIO_CHANNEL(s->sioc), "nbd-client");
+    sioc = qio_channel_socket_new();
+    qio_channel_set_name(QIO_CHANNEL(sioc), "nbd-client");

-    qio_channel_socket_connect_sync(s->sioc, saddr, errp);
+    qio_channel_socket_connect_sync(sioc, saddr, errp);
     if (*errp) {
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
-        return -1;
+        object_unref(OBJECT(sioc));
+        return NULL;
     }

     yank_register_function(BLOCKDEV_YANK_INSTANCE(bs->node_name), nbd_yank, bs);
-    qio_channel_set_delay(QIO_CHANNEL(s->sioc), false);
+    qio_channel_set_delay(QIO_CHANNEL(sioc), false);

-    return 0;
+    return sioc;
 }

-/* nbd_client_handshake takes ownership on s->sioc. On failure it's unref'ed. */
-static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
+/* nbd_client_handshake takes ownership on sioc. */
+static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
+                                Error **errp)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     AioContext *aio_context = bdrv_get_aio_context(bs);
     int ret;

     trace_nbd_client_handshake(s->export);
-    qio_channel_set_blocking(QIO_CHANNEL(s->sioc), false, NULL);
-    qio_channel_attach_aio_context(QIO_CHANNEL(s->sioc), aio_context);
+    qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
+    qio_channel_attach_aio_context(QIO_CHANNEL(sioc), aio_context);

     s->info.request_sizes = true;
     s->info.structured_reply = true;
     s->info.base_allocation = true;
     s->info.x_dirty_bitmap = g_strdup(s->x_dirty_bitmap);
     s->info.name = g_strdup(s->export ?: "");
-    ret = nbd_receive_negotiate(aio_context, QIO_CHANNEL(s->sioc), s->tlscreds,
+    ret = nbd_receive_negotiate(aio_context, QIO_CHANNEL(sioc), s->tlscreds,
                                 s->hostname, &s->ioc, &s->info, errp);
     g_free(s->info.x_dirty_bitmap);
     g_free(s->info.name);
     if (ret < 0) {
         yank_unregister_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
                                  nbd_yank, bs);
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
+        object_unref(OBJECT(sioc));
         return ret;
     }

+    if (s->ioc) {
+        /* sioc is referenced by s->ioc */
+        object_unref(OBJECT(sioc));
+    } else {
+        s->ioc = QIO_CHANNEL(sioc);
+    }
+    sioc = NULL;
+
     ret = nbd_handle_updated_info(bs, errp);
     if (ret < 0) {
         /*
@@ -1640,23 +1644,15 @@ static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
          */
         NBDRequest request = { .type = NBD_CMD_DISC };

-        nbd_send_request(s->ioc ?: QIO_CHANNEL(s->sioc), &request);
+        nbd_send_request(s->ioc, &request);

         yank_unregister_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
                                  nbd_yank, bs);
-        object_unref(OBJECT(s->sioc));
-        s->sioc = NULL;
         object_unref(OBJECT(s->ioc));
         s->ioc = NULL;
-
         return ret;
     }

-    if (!s->ioc) {
-        s->ioc = QIO_CHANNEL(s->sioc);
-        object_ref(OBJECT(s->ioc));
-    }
-
     return 0;
 }

@@ -2048,6 +2044,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
 {
     int ret;
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    QIOChannelSocket *sioc;

     s->bs = bs;
     qemu_co_mutex_init(&s->send_mutex);
@@ -2069,12 +2066,13 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
      * establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
      */
-    if (nbd_establish_connection(bs, s->saddr, errp) < 0) {
+    sioc = nbd_establish_connection(bs, s->saddr, errp);
+    if (!sioc) {
         ret = -ECONNREFUSED;
         goto fail;
     }

-    ret = nbd_client_handshake(bs, errp);
+    ret = nbd_client_handshake(bs, sioc, errp);
     if (ret < 0) {
         goto fail;
     }
-- 
2.31.1

[PULL 28/34] nbd/client-connection: return only one io channel

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

block/nbd doesn't need underlying sioc channel anymore. So, we can
update nbd/client-connection interface to return only one top-most io
channel, which is more straight forward.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-27-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/nbd.h     |  4 ++--
 block/nbd.c             | 13 ++-----------
 nbd/client-connection.c | 33 +++++++++++++++++++++++++--------
 3 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 5bb54d831c8a..10c8a0bcca80 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -418,9 +418,9 @@ NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
                                                QCryptoTLSCreds *tlscreds);
 void nbd_client_connection_release(NBDClientConnection *conn);

-QIOChannelSocket *coroutine_fn
+QIOChannel *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
-                            QIOChannel **ioc, Error **errp);
+                            Error **errp);

 void coroutine_fn nbd_co_establish_connection_cancel(NBDClientConnection *conn);

diff --git a/block/nbd.c b/block/nbd.c
index 9f193d130bcd..411435c1559e 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -360,7 +360,6 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
     AioContext *aio_context = bdrv_get_aio_context(s->bs);
-    QIOChannelSocket *sioc;

     if (!nbd_client_connecting(s)) {
         return;
@@ -399,20 +398,12 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    sioc = nbd_co_establish_connection(s->conn, &s->info, &s->ioc, NULL);
-    if (!sioc) {
+    s->ioc = nbd_co_establish_connection(s->conn, &s->info, NULL);
+    if (!s->ioc) {
         ret = -ECONNREFUSED;
         goto out;
     }

-    if (s->ioc) {
-        /* sioc is referenced by s->ioc */
-        object_unref(OBJECT(sioc));
-    } else {
-        s->ioc = QIO_CHANNEL(sioc);
-    }
-    sioc = NULL;
-
     qio_channel_set_blocking(QIO_CHANNEL(s->ioc), false, NULL);
     qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), aio_context);

diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 883f9cf158cb..72138a5ff74a 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -272,15 +272,15 @@ void nbd_client_connection_release(NBDClientConnection *conn)
  * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
  * include/block/nbd.h).
  */
-QIOChannelSocket *coroutine_fn
+QIOChannel *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
-                            QIOChannel **ioc, Error **errp)
+                            Error **errp)
 {
+    QIOChannel *ioc;
     QemuThread thread;

     if (conn->do_negotiation) {
         assert(info);
-        assert(ioc);
     }

     WITH_QEMU_LOCK_GUARD(&conn->mutex) {
@@ -294,10 +294,17 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
             if (conn->sioc) {
                 /* Previous attempt finally succeeded in background */
                 if (conn->do_negotiation) {
-                    *ioc = g_steal_pointer(&conn->ioc);
+                    ioc = g_steal_pointer(&conn->ioc);
                     memcpy(info, &conn->updated_info, sizeof(*info));
                 }
-                return g_steal_pointer(&conn->sioc);
+                if (ioc) {
+                    /* TLS channel now has own reference to parent */
+                    object_unref(OBJECT(conn->sioc));
+                } else {
+                    ioc = QIO_CHANNEL(conn->sioc);
+                }
+                conn->sioc = NULL;
+                return ioc;
             }

             conn->running = true;
@@ -329,11 +336,21 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
         } else {
             error_propagate(errp, conn->err);
             conn->err = NULL;
-            if (conn->sioc && conn->do_negotiation) {
-                *ioc = g_steal_pointer(&conn->ioc);
+            if (!conn->sioc) {
+                return NULL;
+            }
+            if (conn->do_negotiation) {
+                ioc = g_steal_pointer(&conn->ioc);
                 memcpy(info, &conn->updated_info, sizeof(*info));
             }
-            return g_steal_pointer(&conn->sioc);
+            if (ioc) {
+                /* TLS channel now has own reference to parent */
+                object_unref(OBJECT(conn->sioc));
+            } else {
+                ioc = QIO_CHANNEL(conn->sioc);
+            }
+            conn->sioc = NULL;
+            return ioc;
         }
     }

-- 
2.31.1

Re: [PULL 28/34] nbd/client-connection: return only one io channel

[Vladimir Sementsov-Ogievskiy]

15.06.2021 23:47, Eric Blake wrote:
> From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> 
> block/nbd doesn't need underlying sioc channel anymore. So, we can
> update nbd/client-connection interface to return only one top-most io
> channel, which is more straight forward.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Message-Id: <20210610100802.5888-27-vsementsov@virtuozzo.com>
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>   include/block/nbd.h     |  4 ++--
>   block/nbd.c             | 13 ++-----------
>   nbd/client-connection.c | 33 +++++++++++++++++++++++++--------
>   3 files changed, 29 insertions(+), 21 deletions(-)
> 
> diff --git a/include/block/nbd.h b/include/block/nbd.h
> index 5bb54d831c8a..10c8a0bcca80 100644
> --- a/include/block/nbd.h
> +++ b/include/block/nbd.h
> @@ -418,9 +418,9 @@ NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
>                                                  QCryptoTLSCreds *tlscreds);
>   void nbd_client_connection_release(NBDClientConnection *conn);
> 
> -QIOChannelSocket *coroutine_fn
> +QIOChannel *coroutine_fn
>   nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
> -                            QIOChannel **ioc, Error **errp);
> +                            Error **errp);
> 
>   void coroutine_fn nbd_co_establish_connection_cancel(NBDClientConnection *conn);
> 
> diff --git a/block/nbd.c b/block/nbd.c
> index 9f193d130bcd..411435c1559e 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -360,7 +360,6 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
>   {
>       int ret;
>       AioContext *aio_context = bdrv_get_aio_context(s->bs);
> -    QIOChannelSocket *sioc;
> 
>       if (!nbd_client_connecting(s)) {
>           return;
> @@ -399,20 +398,12 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
>           s->ioc = NULL;
>       }
> 
> -    sioc = nbd_co_establish_connection(s->conn, &s->info, &s->ioc, NULL);
> -    if (!sioc) {
> +    s->ioc = nbd_co_establish_connection(s->conn, &s->info, NULL);
> +    if (!s->ioc) {
>           ret = -ECONNREFUSED;
>           goto out;
>       }
> 
> -    if (s->ioc) {
> -        /* sioc is referenced by s->ioc */
> -        object_unref(OBJECT(sioc));
> -    } else {
> -        s->ioc = QIO_CHANNEL(sioc);
> -    }
> -    sioc = NULL;
> -
>       qio_channel_set_blocking(QIO_CHANNEL(s->ioc), false, NULL);
>       qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), aio_context);
> 
> diff --git a/nbd/client-connection.c b/nbd/client-connection.c
> index 883f9cf158cb..72138a5ff74a 100644
> --- a/nbd/client-connection.c
> +++ b/nbd/client-connection.c
> @@ -272,15 +272,15 @@ void nbd_client_connection_release(NBDClientConnection *conn)
>    * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
>    * include/block/nbd.h).
>    */
> -QIOChannelSocket *coroutine_fn
> +QIOChannel *coroutine_fn
>   nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
> -                            QIOChannel **ioc, Error **errp)
> +                            Error **errp)
>   {
> +    QIOChannel *ioc;
>       QemuThread thread;
> 
>       if (conn->do_negotiation) {
>           assert(info);
> -        assert(ioc);
>       }
> 
>       WITH_QEMU_LOCK_GUARD(&conn->mutex) {
> @@ -294,10 +294,17 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
>               if (conn->sioc) {
>                   /* Previous attempt finally succeeded in background */
>                   if (conn->do_negotiation) {
> -                    *ioc = g_steal_pointer(&conn->ioc);
> +                    ioc = g_steal_pointer(&conn->ioc);
>                       memcpy(info, &conn->updated_info, sizeof(*info));
>                   }
> -                return g_steal_pointer(&conn->sioc);
> +                if (ioc) {
> +                    /* TLS channel now has own reference to parent */
> +                    object_unref(OBJECT(conn->sioc));
> +                } else {
> +                    ioc = QIO_CHANNEL(conn->sioc);
> +                }
> +                conn->sioc = NULL;
> +                return ioc;
>               }
> 
>               conn->running = true;
> @@ -329,11 +336,21 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
>           } else {
>               error_propagate(errp, conn->err);
>               conn->err = NULL;
> -            if (conn->sioc && conn->do_negotiation) {
> -                *ioc = g_steal_pointer(&conn->ioc);
> +            if (!conn->sioc) {
> +                return NULL;
> +            }
> +            if (conn->do_negotiation) {
> +                ioc = g_steal_pointer(&conn->ioc);
>                   memcpy(info, &conn->updated_info, sizeof(*info));
>               }
> -            return g_steal_pointer(&conn->sioc);
> +            if (ioc) {
> +                /* TLS channel now has own reference to parent */
> +                object_unref(OBJECT(conn->sioc));
> +            } else {
> +                ioc = QIO_CHANNEL(conn->sioc);
> +            }
> +            conn->sioc = NULL;
> +            return ioc;
>           }
>       }
> 

Logic is wrong and uninitialized use of ioc really possible, as Peter (and clang) reports.

So, I propose the following squash-in. It doesn't conflict with following patches.

squash-in:

diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 500b8591e8..396d7f17f0 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -275,7 +275,6 @@ QIOChannel *coroutine_fn
  nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
                              Error **errp)
  {
-    QIOChannel *ioc;
      QemuThread thread;
  
      if (conn->do_negotiation) {
@@ -293,17 +292,19 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
              if (conn->sioc) {
                  /* Previous attempt finally succeeded in background */
                  if (conn->do_negotiation) {
-                    ioc = g_steal_pointer(&conn->ioc);
                      memcpy(info, &conn->updated_info, sizeof(*info));
+                    if (conn->ioc) {
+                        /* TLS channel now has own reference to parent */
+                        object_unref(OBJECT(conn->sioc));
+                        conn->sioc = NULL;
+
+                        return g_steal_pointer(&conn->ioc);
+                    }
                  }
-                if (ioc) {
-                    /* TLS channel now has own reference to parent */
-                    object_unref(OBJECT(conn->sioc));
-                } else {
-                    ioc = QIO_CHANNEL(conn->sioc);
-                }
-                conn->sioc = NULL;
-                return ioc;
+
+                assert(!conn->ioc);
+
+                return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
              }
  
              conn->running = true;
@@ -339,17 +340,19 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
                  return NULL;
              }
              if (conn->do_negotiation) {
-                ioc = g_steal_pointer(&conn->ioc);
                  memcpy(info, &conn->updated_info, sizeof(*info));
+                if (conn->ioc) {
+                    /* TLS channel now has own reference to parent */
+                    object_unref(OBJECT(conn->sioc));
+                    conn->sioc = NULL;
+
+                    return g_steal_pointer(&conn->ioc);
+                }
              }
-            if (ioc) {
-                /* TLS channel now has own reference to parent */
-                object_unref(OBJECT(conn->sioc));
-            } else {
-                ioc = QIO_CHANNEL(conn->sioc);
-            }
-            conn->sioc = NULL;
-            return ioc;
+
+            assert(!conn->ioc);
+
+            return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
          }
      }
  




-- 
Best regards,
Vladimir

Re: [PULL 28/34] nbd/client-connection: return only one io channel

[Eric Blake]

On Thu, Jun 17, 2021 at 09:32:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Logic is wrong and uninitialized use of ioc really possible, as Peter (and clang) reports.
> 
> So, I propose the following squash-in. It doesn't conflict with following patches.
> 
> squash-in:
> 
> diff --git a/nbd/client-connection.c b/nbd/client-connection.c
> index 500b8591e8..396d7f17f0 100644
> --- a/nbd/client-connection.c
> +++ b/nbd/client-connection.c
> @@ -275,7 +275,6 @@ QIOChannel *coroutine_fn
>  nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
>                              Error **errp)
>  {
> -    QIOChannel *ioc;
>      QemuThread thread;
>      if (conn->do_negotiation) {
> @@ -293,17 +292,19 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
>              if (conn->sioc) {
>                  /* Previous attempt finally succeeded in background */
>                  if (conn->do_negotiation) {
> -                    ioc = g_steal_pointer(&conn->ioc);
>                      memcpy(info, &conn->updated_info, sizeof(*info));
> +                    if (conn->ioc) {
> +                        /* TLS channel now has own reference to parent */
> +                        object_unref(OBJECT(conn->sioc));
> +                        conn->sioc = NULL;
> +
> +                        return g_steal_pointer(&conn->ioc);
> +                    }
>                  }
> -                if (ioc) {
> -                    /* TLS channel now has own reference to parent */
> -                    object_unref(OBJECT(conn->sioc));
> -                } else {
> -                    ioc = QIO_CHANNEL(conn->sioc);
> -                }
> -                conn->sioc = NULL;
> -                return ioc;
> +
> +                assert(!conn->ioc);
> +
> +                return QIO_CHANNEL(g_steal_pointer(&conn->sioc));

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

I'll squash this in and send v2 of the pull request

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

[PULL 29/34] block-coroutine-wrapper: allow non bdrv_ prefix

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We are going to reuse the script to generate a nbd_ function in
further commit. Prepare the script now.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-28-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 scripts/block-coroutine-wrapper.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/scripts/block-coroutine-wrapper.py b/scripts/block-coroutine-wrapper.py
index 0461fd1c459c..85dbeb9ecf9c 100644
--- a/scripts/block-coroutine-wrapper.py
+++ b/scripts/block-coroutine-wrapper.py
@@ -98,12 +98,13 @@ def snake_to_camel(func_name: str) -> str:


 def gen_wrapper(func: FuncDecl) -> str:
-    assert func.name.startswith('bdrv_')
-    assert not func.name.startswith('bdrv_co_')
+    assert not '_co_' in func.name
     assert func.return_type == 'int'
     assert func.args[0].type in ['BlockDriverState *', 'BdrvChild *']

-    name = 'bdrv_co_' + func.name[5:]
+    subsystem, subname = func.name.split('_', 1)
+
+    name = f'{subsystem}_co_{subname}'
     bs = 'bs' if func.args[0].type == 'BlockDriverState *' else 'child->bs'
     struct_name = snake_to_camel(name)

-- 
2.31.1

[PULL 30/34] block/nbd: split nbd_co_do_establish_connection out of nbd_reconnect_attempt

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Split out the part that we want to reuse for nbd_open().

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610100802.5888-29-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 82 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 43 insertions(+), 39 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 411435c1559e..8caeafc8d351 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -356,11 +356,50 @@ static int nbd_handle_updated_info(BlockDriverState *bs, Error **errp)
     return 0;
 }

+static int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
+                                                       Error **errp)
+{
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    int ret;
+
+    assert(!s->ioc);
+
+    s->ioc = nbd_co_establish_connection(s->conn, &s->info, errp);
+    if (!s->ioc) {
+        return -ECONNREFUSED;
+    }
+
+    ret = nbd_handle_updated_info(s->bs, NULL);
+    if (ret < 0) {
+        /*
+         * We have connected, but must fail for other reasons.
+         * Send NBD_CMD_DISC as a courtesy to the server.
+         */
+        NBDRequest request = { .type = NBD_CMD_DISC };
+
+        nbd_send_request(s->ioc, &request);
+
+        object_unref(OBJECT(s->ioc));
+        s->ioc = NULL;
+
+        return ret;
+    }
+
+    qio_channel_set_blocking(s->ioc, false, NULL);
+    qio_channel_attach_aio_context(s->ioc, bdrv_get_aio_context(bs));
+
+    yank_register_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name), nbd_yank,
+                           bs);
+
+    /* successfully connected */
+    s->state = NBD_CLIENT_CONNECTED;
+    qemu_co_queue_restart_all(&s->free_sema);
+
+    return 0;
+}
+
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
-    int ret;
-    AioContext *aio_context = bdrv_get_aio_context(s->bs);
-
     if (!nbd_client_connecting(s)) {
         return;
     }
@@ -398,42 +437,7 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    s->ioc = nbd_co_establish_connection(s->conn, &s->info, NULL);
-    if (!s->ioc) {
-        ret = -ECONNREFUSED;
-        goto out;
-    }
-
-    qio_channel_set_blocking(QIO_CHANNEL(s->ioc), false, NULL);
-    qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), aio_context);
-
-    yank_register_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name), nbd_yank,
-                           s->bs);
-
-    ret = nbd_handle_updated_info(s->bs, NULL);
-    if (ret < 0) {
-        /*
-         * We have connected, but must fail for other reasons.
-         * Send NBD_CMD_DISC as a courtesy to the server.
-         */
-        NBDRequest request = { .type = NBD_CMD_DISC };
-
-        nbd_send_request(s->ioc, &request);
-
-        yank_unregister_function(BLOCKDEV_YANK_INSTANCE(s->bs->node_name),
-                                 nbd_yank, s->bs);
-        object_unref(OBJECT(s->ioc));
-        s->ioc = NULL;
-
-        return;
-    }
-
-out:
-    if (ret >= 0) {
-        /* successfully connected */
-        s->state = NBD_CLIENT_CONNECTED;
-        qemu_co_queue_restart_all(&s->free_sema);
-    }
+    nbd_co_do_establish_connection(s->bs, NULL);
 }

 static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
-- 
2.31.1

[PULL 31/34] nbd/client-connection: add option for non-blocking connection attempt

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We'll need a possibility of non-blocking nbd_co_establish_connection(),
so that it returns immediately, and it returns success only if a
connections was previously established in background.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-30-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/nbd.h     | 2 +-
 block/nbd.c             | 2 +-
 nbd/client-connection.c | 8 +++++++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 10c8a0bcca80..78d101b77488 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -420,7 +420,7 @@ void nbd_client_connection_release(NBDClientConnection *conn);

 QIOChannel *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
-                            Error **errp);
+                            bool blocking, Error **errp);

 void coroutine_fn nbd_co_establish_connection_cancel(NBDClientConnection *conn);

diff --git a/block/nbd.c b/block/nbd.c
index 8caeafc8d351..bf2e9393146b 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -364,7 +364,7 @@ static int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,

     assert(!s->ioc);

-    s->ioc = nbd_co_establish_connection(s->conn, &s->info, errp);
+    s->ioc = nbd_co_establish_connection(s->conn, &s->info, true, errp);
     if (!s->ioc) {
         return -ECONNREFUSED;
     }
diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 72138a5ff74a..aff646028786 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -266,6 +266,8 @@ void nbd_client_connection_release(NBDClientConnection *conn)
  *   otherwise the thread is not running, so start a thread and wait for
  *     completion
  *
+ * If @blocking is false, don't wait for the thread, return immediately.
+ *
  * If @info is not NULL, also do nbd-negotiation after successful connection.
  * In this case info is used only as out parameter, and is fully initialized by
  * nbd_co_establish_connection(). "IN" fields of info as well as related only to
@@ -274,7 +276,7 @@ void nbd_client_connection_release(NBDClientConnection *conn)
  */
 QIOChannel *coroutine_fn
 nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
-                            Error **errp)
+                            bool blocking, Error **errp)
 {
     QIOChannel *ioc;
     QemuThread thread;
@@ -314,6 +316,10 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
                                connect_thread_func, conn, QEMU_THREAD_DETACHED);
         }

+        if (!blocking) {
+            return NULL;
+        }
+
         conn->wait_co = qemu_coroutine_self();
     }

-- 
2.31.1

[PULL 32/34] block/nbd: reuse nbd_co_do_establish_connection() in nbd_open()

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

The only last step we need to reuse the function is coroutine-wrapper.
nbd_open() may be called from non-coroutine context. So, generate the
wrapper and use it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-31-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/coroutines.h |   6 +++
 block/nbd.c        | 103 +++------------------------------------------
 2 files changed, 11 insertions(+), 98 deletions(-)

diff --git a/block/coroutines.h b/block/coroutines.h
index 4cfb4946e65e..514d169d23d6 100644
--- a/block/coroutines.h
+++ b/block/coroutines.h
@@ -66,4 +66,10 @@ int coroutine_fn bdrv_co_readv_vmstate(BlockDriverState *bs,
 int coroutine_fn bdrv_co_writev_vmstate(BlockDriverState *bs,
                                         QEMUIOVector *qiov, int64_t pos);

+int generated_co_wrapper
+nbd_do_establish_connection(BlockDriverState *bs, Error **errp);
+int coroutine_fn
+nbd_co_do_establish_connection(BlockDriverState *bs, Error **errp);
+
+
 #endif /* BLOCK_COROUTINES_INT_H */
diff --git a/block/nbd.c b/block/nbd.c
index bf2e9393146b..5e7e238b4790 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -44,6 +44,7 @@
 #include "block/qdict.h"
 #include "block/nbd.h"
 #include "block/block_int.h"
+#include "block/coroutines.h"

 #include "qemu/yank.h"

@@ -99,11 +100,6 @@ typedef struct BDRVNBDState {
     NBDClientConnection *conn;
 } BDRVNBDState;

-static QIOChannelSocket *nbd_establish_connection(BlockDriverState *bs,
-                                                  SocketAddress *saddr,
-                                                  Error **errp);
-static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
-                                Error **errp);
 static void nbd_yank(void *opaque);

 static void nbd_clear_bdrvstate(BlockDriverState *bs)
@@ -356,8 +352,8 @@ static int nbd_handle_updated_info(BlockDriverState *bs, Error **errp)
     return 0;
 }

-static int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
-                                                       Error **errp)
+int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
+                                                Error **errp)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     int ret;
@@ -1573,83 +1569,6 @@ static void nbd_client_close(BlockDriverState *bs)
     nbd_teardown_connection(bs);
 }

-static QIOChannelSocket *nbd_establish_connection(BlockDriverState *bs,
-                                                  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;
-    }
-
-    yank_register_function(BLOCKDEV_YANK_INSTANCE(bs->node_name), nbd_yank, bs);
-    qio_channel_set_delay(QIO_CHANNEL(sioc), false);
-
-    return sioc;
-}
-
-/* nbd_client_handshake takes ownership on sioc. */
-static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
-                                Error **errp)
-{
-    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
-    AioContext *aio_context = bdrv_get_aio_context(bs);
-    int ret;
-
-    trace_nbd_client_handshake(s->export);
-    qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
-    qio_channel_attach_aio_context(QIO_CHANNEL(sioc), aio_context);
-
-    s->info.request_sizes = true;
-    s->info.structured_reply = true;
-    s->info.base_allocation = true;
-    s->info.x_dirty_bitmap = g_strdup(s->x_dirty_bitmap);
-    s->info.name = g_strdup(s->export ?: "");
-    ret = nbd_receive_negotiate(aio_context, QIO_CHANNEL(sioc), s->tlscreds,
-                                s->hostname, &s->ioc, &s->info, errp);
-    g_free(s->info.x_dirty_bitmap);
-    g_free(s->info.name);
-    if (ret < 0) {
-        yank_unregister_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
-                                 nbd_yank, bs);
-        object_unref(OBJECT(sioc));
-        return ret;
-    }
-
-    if (s->ioc) {
-        /* sioc is referenced by s->ioc */
-        object_unref(OBJECT(sioc));
-    } else {
-        s->ioc = QIO_CHANNEL(sioc);
-    }
-    sioc = NULL;
-
-    ret = nbd_handle_updated_info(bs, errp);
-    if (ret < 0) {
-        /*
-         * We have connected, but must fail for other reasons.
-         * Send NBD_CMD_DISC as a courtesy to the server.
-         */
-        NBDRequest request = { .type = NBD_CMD_DISC };
-
-        nbd_send_request(s->ioc, &request);
-
-        yank_unregister_function(BLOCKDEV_YANK_INSTANCE(bs->node_name),
-                                 nbd_yank, bs);
-        object_unref(OBJECT(s->ioc));
-        s->ioc = NULL;
-        return ret;
-    }
-
-    return 0;
-}

 /*
  * Parse nbd_open options
@@ -2039,7 +1958,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
 {
     int ret;
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
-    QIOChannelSocket *sioc;

     s->bs = bs;
     qemu_co_mutex_init(&s->send_mutex);
@@ -2057,22 +1975,11 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     s->conn = nbd_client_connection_new(s->saddr, true, s->export,
                                         s->x_dirty_bitmap, s->tlscreds);

-    /*
-     * establish TCP connection, return error if it fails
-     * TODO: Configurable retry-until-timeout behaviour.
-     */
-    sioc = nbd_establish_connection(bs, s->saddr, errp);
-    if (!sioc) {
-        ret = -ECONNREFUSED;
-        goto fail;
-    }
-
-    ret = nbd_client_handshake(bs, sioc, errp);
+    /* TODO: Configurable retry-until-timeout behaviour. */
+    ret = nbd_do_establish_connection(bs, errp);
     if (ret < 0) {
         goto fail;
     }
-    /* successfully connected */
-    s->state = NBD_CLIENT_CONNECTED;

     s->connection_co = qemu_coroutine_create(nbd_connection_entry, s);
     bdrv_inc_in_flight(bs);
-- 
2.31.1

[PULL 33/34] block/nbd: add nbd_client_connected() helper

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We already have two similar helpers for other state. Let's add another
one for convenience.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-32-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 5e7e238b4790..5cfb749e089d 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -122,15 +122,20 @@ static void nbd_clear_bdrvstate(BlockDriverState *bs)
     s->x_dirty_bitmap = NULL;
 }

+static bool nbd_client_connected(BDRVNBDState *s)
+{
+    return qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTED;
+}
+
 static void nbd_channel_error(BDRVNBDState *s, int ret)
 {
     if (ret == -EIO) {
-        if (qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTED) {
+        if (nbd_client_connected(s)) {
             s->state = s->reconnect_delay ? NBD_CLIENT_CONNECTING_WAIT :
                                             NBD_CLIENT_CONNECTING_NOWAIT;
         }
     } else {
-        if (qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTED) {
+        if (nbd_client_connected(s)) {
             qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
         }
         s->state = NBD_CLIENT_QUIT;
@@ -228,7 +233,7 @@ static void nbd_client_attach_aio_context(BlockDriverState *bs,
      * s->connection_co is either yielded from nbd_receive_reply or from
      * nbd_co_reconnect_loop()
      */
-    if (qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTED) {
+    if (nbd_client_connected(s)) {
         qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), new_context);
     }

@@ -499,7 +504,7 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
             nbd_co_reconnect_loop(s);
         }

-        if (qatomic_load_acquire(&s->state) != NBD_CLIENT_CONNECTED) {
+        if (!nbd_client_connected(s)) {
             continue;
         }

@@ -578,7 +583,7 @@ static int nbd_co_send_request(BlockDriverState *bs,
         qemu_co_queue_wait(&s->free_sema, &s->send_mutex);
     }

-    if (qatomic_load_acquire(&s->state) != NBD_CLIENT_CONNECTED) {
+    if (!nbd_client_connected(s)) {
         rc = -EIO;
         goto err;
     }
@@ -605,8 +610,7 @@ static int nbd_co_send_request(BlockDriverState *bs,
     if (qiov) {
         qio_channel_set_cork(s->ioc, true);
         rc = nbd_send_request(s->ioc, request);
-        if (qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTED &&
-            rc >= 0) {
+        if (nbd_client_connected(s) && rc >= 0) {
             if (qio_channel_writev_all(s->ioc, qiov->iov, qiov->niov,
                                        NULL) < 0) {
                 rc = -EIO;
@@ -931,7 +935,7 @@ static coroutine_fn int nbd_co_do_receive_one_chunk(
     s->requests[i].receiving = true;
     qemu_coroutine_yield();
     s->requests[i].receiving = false;
-    if (qatomic_load_acquire(&s->state) != NBD_CLIENT_CONNECTED) {
+    if (!nbd_client_connected(s)) {
         error_setg(errp, "Connection closed");
         return -EIO;
     }
@@ -1090,7 +1094,7 @@ static bool nbd_reply_chunk_iter_receive(BDRVNBDState *s,
     NBDReply local_reply;
     NBDStructuredReplyChunk *chunk;
     Error *local_err = NULL;
-    if (qatomic_load_acquire(&s->state) != NBD_CLIENT_CONNECTED) {
+    if (!nbd_client_connected(s)) {
         error_setg(&local_err, "Connection closed");
         nbd_iter_channel_error(iter, -EIO, &local_err);
         goto break_loop;
@@ -1115,8 +1119,7 @@ static bool nbd_reply_chunk_iter_receive(BDRVNBDState *s,
     }

     /* Do not execute the body of NBD_FOREACH_REPLY_CHUNK for simple reply. */
-    if (nbd_reply_is_simple(reply) ||
-        qatomic_load_acquire(&s->state) != NBD_CLIENT_CONNECTED) {
+    if (nbd_reply_is_simple(reply) || !nbd_client_connected(s)) {
         goto break_loop;
     }

-- 
2.31.1

[PULL 34/34] block/nbd: safer transition to receiving request

[Eric Blake]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

req->receiving is a flag of request being in one concrete yield point
in nbd_co_do_receive_one_chunk().

Such kind of boolean flag is always better to unset before scheduling
the coroutine, to avoid double scheduling. So, let's be more careful.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-33-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/nbd.c b/block/nbd.c
index 5cfb749e089d..3cbee762de8d 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -150,6 +150,7 @@ static void nbd_recv_coroutines_wake_all(BDRVNBDState *s)
         NBDClientRequest *req = &s->requests[i];

         if (req->coroutine && req->receiving) {
+            req->receiving = false;
             aio_co_wake(req->coroutine);
         }
     }
@@ -548,6 +549,7 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
          *   connection_co happens through a bottom half, which can only
          *   run after we yield.
          */
+        s->requests[i].receiving = false;
         aio_co_wake(s->requests[i].coroutine);
         qemu_coroutine_yield();
     }
@@ -934,7 +936,7 @@ static coroutine_fn int nbd_co_do_receive_one_chunk(
     /* Wait until we're woken up by nbd_connection_entry.  */
     s->requests[i].receiving = true;
     qemu_coroutine_yield();
-    s->requests[i].receiving = false;
+    assert(!s->requests[i].receiving);
     if (!nbd_client_connected(s)) {
         error_setg(errp, "Connection closed");
         return -EIO;
-- 
2.31.1

Re: [PULL 00/34] NBD patches for 2021-06-15

[Peter Maydell]

On Tue, 15 Jun 2021 at 21:50, Eric Blake <eblake@redhat.com> wrote:
>
> The following changes since commit 1ea06abceec61b6f3ab33dadb0510b6e09fb61e2:
>
>   Merge remote-tracking branch 'remotes/berrange-gitlab/tags/misc-fixes-pull-request' into staging (2021-06-14 15:59:13 +0100)
>
> are available in the Git repository at:
>
>   https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2021-06-15
>
> for you to fetch changes up to 788b68b57dea4ddd0038f73b96c147eb406c386d:
>
>   block/nbd: safer transition to receiving request (2021-06-15 15:42:33 -0500)
>
> ----------------------------------------------------------------
> nbd patches for 2021-06-15
>
> - bug fixes in coroutine aio context handling
> - rework NBD client connection logic to perform more work in coroutine
> rather than blocking main loop

Fails to compile, all hosts:

../../nbd/client-connection.c: In function ‘nbd_co_establish_connection’:
../../nbd/client-connection.c:352:16: error: ‘ioc’ may be used uninitialized in
this function [-Werror=maybe-uninitialized]
  352 |             if (ioc) {
      |                ^


clang is more specific:


../../nbd/client-connection.c:298:21: error: variable 'ioc' is used
uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
                if (conn->do_negotiation) {
                    ^~~~~~~~~~~~~~~~~~~~
../../nbd/client-connection.c:302:21: note: uninitialized use occurs here
                if (ioc) {
                    ^~~
../../nbd/client-connection.c:298:17: note: remove the 'if' if its
condition is always true
                if (conn->do_negotiation) {
                ^~~~~~~~~~~~~~~~~~~~~~~~~~
../../nbd/client-connection.c:281:20: note: initialize the variable
'ioc' to silence this warning
    QIOChannel *ioc;
                   ^
                    = NULL
1 error generated.


thanks
-- PMM

Re: [PULL 00/34] NBD patches for 2021-06-15

[Vladimir Sementsov-Ogievskiy]

17.06.2021 12:42, Peter Maydell wrote:
> On Tue, 15 Jun 2021 at 21:50, Eric Blake <eblake@redhat.com> wrote:
>>
>> The following changes since commit 1ea06abceec61b6f3ab33dadb0510b6e09fb61e2:
>>
>>    Merge remote-tracking branch 'remotes/berrange-gitlab/tags/misc-fixes-pull-request' into staging (2021-06-14 15:59:13 +0100)
>>
>> are available in the Git repository at:
>>
>>    https://repo.or.cz/qemu/ericb.git tags/pull-nbd-2021-06-15
>>
>> for you to fetch changes up to 788b68b57dea4ddd0038f73b96c147eb406c386d:
>>
>>    block/nbd: safer transition to receiving request (2021-06-15 15:42:33 -0500)
>>
>> ----------------------------------------------------------------
>> nbd patches for 2021-06-15
>>
>> - bug fixes in coroutine aio context handling
>> - rework NBD client connection logic to perform more work in coroutine
>> rather than blocking main loop
> 
> Fails to compile, all hosts:
> 
> ../../nbd/client-connection.c: In function ‘nbd_co_establish_connection’:
> ../../nbd/client-connection.c:352:16: error: ‘ioc’ may be used uninitialized in
> this function [-Werror=maybe-uninitialized]
>    352 |             if (ioc) {
>        |                ^
> 
> 
> clang is more specific:
> 
> 
> ../../nbd/client-connection.c:298:21: error: variable 'ioc' is used
> uninitialized whenever 'if' condition is false
> [-Werror,-Wsometimes-uninitialized]
>                  if (conn->do_negotiation) {
>                      ^~~~~~~~~~~~~~~~~~~~
> ../../nbd/client-connection.c:302:21: note: uninitialized use occurs here
>                  if (ioc) {
>                      ^~~
> ../../nbd/client-connection.c:298:17: note: remove the 'if' if its
> condition is always true
>                  if (conn->do_negotiation) {
>                  ^~~~~~~~~~~~~~~~~~~~~~~~~~
> ../../nbd/client-connection.c:281:20: note: initialize the variable
> 'ioc' to silence this warning
>      QIOChannel *ioc;
>                     ^
>                      = NULL
> 1 error generated.
> 


Sorry for this :(

Only one patch needs fixing: 28. I posted a squash-in. Eric, could you please take a look and make a v2 of pull request?


-- 
Best regards,
Vladimir