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nbd: move connection code from block/nbd to nbd/client-connection
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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>
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@ebblake
Vladimir Sementsov-Ogievskiy authored and ebblake committed Jun 15, 2021
1 parent 597d438 commit 996623e
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Showing 4 changed files with 244 additions and 207 deletions.
207 changes: 0 additions & 207 deletions block/nbd.c
View file
Expand Up @@ -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) */
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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;
Expand Down
11 changes: 11 additions & 0 deletions include/block/nbd.h
View file
Expand Up @@ -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

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