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migration/multifd: Unify multifd and TLS connection paths 

During multifd channel creation (multifd_send_new_channel_async) when
TLS is enabled, the multifd_channel_connect function is called twice,
once to create the TLS handshake thread and another time after the
asynchrounous TLS handshake has finished.

This creates a slightly confusing call stack where
multifd_channel_connect() is called more times than the number of
channels. It also splits error handling between the two callers of
multifd_channel_connect() causing some code duplication. Lastly, it
gets in the way of having a single point to determine whether all
channel creation tasks have been initiated.

Refactor the code to move the reentrancy one level up at the
multifd_new_send_channel_async() level, de-duplicating the error
handling and allowing for the next patch to introduce a
synchronization point common to all the multifd channel creation,
regardless of TLS.

Note that the previous code would never fail once p->c had been set.
This patch changes this assumption, which affects refcounting, so add
comments around object_unref to explain the situation.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240206215118.6171-6-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Fabiano Rosas 2024-02-06 18:51:17 -03:00 committed by Peter Xu
parent dd904bc13f
commit 2576ae488e
1 changed files with 40 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

83
migration/multifd.c
View File

@ -869,30 +869,7 @@ out:
return NULL;
}
static bool multifd_channel_connect(MultiFDSendParams *p,
QIOChannel *ioc,
Error **errp);
static void multifd_tls_outgoing_handshake(QIOTask *task,
gpointer opaque)
{
MultiFDSendParams *p = opaque;
QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
Error *err = NULL;
if (!qio_task_propagate_error(task, &err)) {
trace_multifd_tls_outgoing_handshake_complete(ioc);
if (multifd_channel_connect(p, ioc, &err)) {
return;
}
}
trace_multifd_tls_outgoing_handshake_error(ioc, error_get_pretty(err));
multifd_send_set_error(err);
multifd_send_kick_main(p);
error_free(err);
}
static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque);
static void *multifd_tls_handshake_thread(void *opaque)
{
@ -900,7 +877,7 @@ static void *multifd_tls_handshake_thread(void *opaque)
QIOChannelTLS *tioc = QIO_CHANNEL_TLS(p->c);
qio_channel_tls_handshake(tioc,
multifd_tls_outgoing_handshake,
multifd_new_send_channel_async,
p,
NULL,
NULL);
@ -920,6 +897,10 @@ static bool multifd_tls_channel_connect(MultiFDSendParams *p,
return false;
}
/*
* Ownership of the socket channel now transfers to the newly
* created TLS channel, which has already taken a reference.
*/
object_unref(OBJECT(ioc));
trace_multifd_tls_outgoing_handshake_start(ioc, tioc, hostname);
qio_channel_set_name(QIO_CHANNEL(tioc), "multifd-tls-outgoing");
@ -936,18 +917,7 @@ static bool multifd_channel_connect(MultiFDSendParams *p,
QIOChannel *ioc,
Error **errp)
{
trace_multifd_set_outgoing_channel(
ioc, object_get_typename(OBJECT(ioc)),
migrate_get_current()->hostname);
if (migrate_channel_requires_tls_upgrade(ioc)) {
/*
* tls_channel_connect will call back to this
* function after the TLS handshake,
* so we mustn't call multifd_send_thread until then
*/
return multifd_tls_channel_connect(p, ioc, errp);
}
qio_channel_set_delay(ioc, false);
migration_ioc_register_yank(ioc);
p->registered_yank = true;
@ -959,24 +929,51 @@ static bool multifd_channel_connect(MultiFDSendParams *p,
return true;
}
/*
* When TLS is enabled this function is called once to establish the
* TLS connection and a second time after the TLS handshake to create
* the multifd channel. Without TLS it goes straight into the channel
* creation.
*/
static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
{
MultiFDSendParams *p = opaque;
QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task));
Error *local_err = NULL;
bool ret;
trace_multifd_new_send_channel_async(p->id);
if (!qio_task_propagate_error(task, &local_err)) {
qio_channel_set_delay(ioc, false);
if (multifd_channel_connect(p, ioc, &local_err)) {
return;
}
if (qio_task_propagate_error(task, &local_err)) {
ret = false;
goto out;
}
trace_multifd_set_outgoing_channel(ioc, object_get_typename(OBJECT(ioc)),
migrate_get_current()->hostname);
if (migrate_channel_requires_tls_upgrade(ioc)) {
ret = multifd_tls_channel_connect(p, ioc, &local_err);
} else {
ret = multifd_channel_connect(p, ioc, &local_err);
}
if (ret) {
return;
}
out:
trace_multifd_new_send_channel_async_error(p->id, local_err);
multifd_send_set_error(local_err);
multifd_send_kick_main(p);
object_unref(OBJECT(ioc));
if (!p->c) {
/*
* If no channel has been created, drop the initial
* reference. Otherwise cleanup happens at
* multifd_send_channel_destroy()
*/
object_unref(OBJECT(ioc));
}
error_free(local_err);
}