diff options
Diffstat (limited to 'nbd')
| -rw-r--r-- | nbd/client-connection.c | 232 | ||||
| -rw-r--r-- | nbd/meson.build | 1 |
2 files changed, 233 insertions, 0 deletions
diff --git a/nbd/client-connection.c b/nbd/client-connection.c new file mode 100644 index 0000000000..f3b270d38c --- /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 2baaa36948..b26d70565e 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( |