nbd patches for 2020-09-02

- fix a few iotests affected by earlier nbd changes
 - avoid blocking qemu by nbd client in connect()
 - build qemu-nbd for mingw
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Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2020-09-02' into staging

nbd patches for 2020-09-02

- fix a few iotests affected by earlier nbd changes
- avoid blocking qemu by nbd client in connect()
- build qemu-nbd for mingw

# gpg: Signature made Wed 02 Sep 2020 22:52:31 BST
# gpg:                using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg:                 aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-nbd-2020-09-02:
  nbd: disable signals and forking on Windows builds
  nbd: skip SIGTERM handler if NBD device support is not built
  block: add missing socket_init() calls to tools
  block/nbd: use non-blocking connect: fix vm hang on connect()
  iotests/259: Fix reference output
  iotests/059: Fix reference output

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

block/nbd.c

@@ -38,6 +38,7 @@
 
 #include "qapi/qapi-visit-sockets.h"
 #include "qapi/qmp/qstring.h"
+#include "qapi/clone-visitor.h"
 
 #include "block/qdict.h"
 #include "block/nbd.h"
@@ -62,6 +63,47 @@ 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 */
+    /*
+     * 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.
+     * If you want to steal error, don't forget to set pointer to NULL.
+     */
+    QIOChannelSocket *sioc;
+    Error *err;
+
+    /* state and bh_ctx are protected by mutex */
+    QemuMutex mutex;
+    NBDConnectThreadState state; /* current state of the thread */
+    AioContext *bh_ctx; /* where to schedule bh (NULL means don't schedule) */
+} NBDConnectThread;
+
 typedef struct BDRVNBDState {
     QIOChannelSocket *sioc; /* The master data channel */
     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
@@ -91,10 +133,17 @@ typedef struct BDRVNBDState {
     QCryptoTLSCreds *tlscreds;
     const char *hostname;
     char *x_dirty_bitmap;
+
+    bool wait_connect;
+    NBDConnectThread *connect_thread;
 } BDRVNBDState;
 
 static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
                                                   Error **errp);
+static QIOChannelSocket *nbd_co_establish_connection(BlockDriverState *bs,
+                                                     Error **errp);
+static void nbd_co_establish_connection_cancel(BlockDriverState *bs,
+                                               bool detach);
 static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
                                 Error **errp);
 
@@ -191,6 +240,8 @@ static void coroutine_fn nbd_client_co_drain_begin(BlockDriverState *bs)
     if (s->connection_co_sleep_ns_state) {
         qemu_co_sleep_wake(s->connection_co_sleep_ns_state);
     }
+
+    nbd_co_establish_connection_cancel(bs, false);
 }
 
 static void coroutine_fn nbd_client_co_drain_end(BlockDriverState *bs)
@@ -223,6 +274,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
         if (s->connection_co_sleep_ns_state) {
             qemu_co_sleep_wake(s->connection_co_sleep_ns_state);
         }
+        nbd_co_establish_connection_cancel(bs, true);
     }
     if (qemu_in_coroutine()) {
         s->teardown_co = qemu_coroutine_self();
@@ -246,6 +298,216 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)
     return 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);
+
+    *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);
+}
+
+static void nbd_free_connect_thread(NBDConnectThread *thr)
+{
+    if (thr->sioc) {
+        qio_channel_close(QIO_CHANNEL(thr->sioc), NULL);
+    }
+    error_free(thr->err);
+    qapi_free_SocketAddress(thr->saddr);
+    g_free(thr);
+}
+
+static void *connect_thread_func(void *opaque)
+{
+    NBDConnectThread *thr = opaque;
+    int ret;
+    bool do_free = false;
+
+    thr->sioc = qio_channel_socket_new();
+
+    error_free(thr->err);
+    thr->err = NULL;
+    ret = qio_channel_socket_connect_sync(thr->sioc, thr->saddr, &thr->err);
+    if (ret < 0) {
+        object_unref(OBJECT(thr->sioc));
+        thr->sioc = NULL;
+    }
+
+    qemu_mutex_lock(&thr->mutex);
+
+    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;
+        }
+        break;
+    case CONNECT_THREAD_RUNNING_DETACHED:
+        do_free = true;
+        break;
+    default:
+        abort();
+    }
+
+    qemu_mutex_unlock(&thr->mutex);
+
+    if (do_free) {
+        nbd_free_connect_thread(thr);
+    }
+
+    return NULL;
+}
+
+static QIOChannelSocket *coroutine_fn
+nbd_co_establish_connection(BlockDriverState *bs, Error **errp)
+{
+    QemuThread thread;
+    BDRVNBDState *s = bs->opaque;
+    QIOChannelSocket *res;
+    NBDConnectThread *thr = s->connect_thread;
+
+    qemu_mutex_lock(&thr->mutex);
+
+    switch (thr->state) {
+    case CONNECT_THREAD_FAIL:
+    case CONNECT_THREAD_NONE:
+        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;
+        res = thr->sioc;
+        thr->sioc = NULL;
+        qemu_mutex_unlock(&thr->mutex);
+        return res;
+    case CONNECT_THREAD_RUNNING:
+        /* Already running, will wait */
+        break;
+    default:
+        abort();
+    }
+
+    thr->bh_ctx = qemu_get_current_aio_context();
+
+    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);
+
+    switch (thr->state) {
+    case CONNECT_THREAD_SUCCESS:
+    case CONNECT_THREAD_FAIL:
+        thr->state = CONNECT_THREAD_NONE;
+        error_propagate(errp, thr->err);
+        thr->err = NULL;
+        res = thr->sioc;
+        thr->sioc = NULL;
+        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.
+         */
+        res = NULL;
+        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 res;
+}
+
+/*
+ * 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)
+{
+    BDRVNBDState *s = bs->opaque;
+    NBDConnectThread *thr = s->connect_thread;
+    bool wake = false;
+    bool do_free = false;
+
+    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;
+        }
+        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);
+    }
+}
+
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
@@ -289,7 +551,7 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }
 
-    sioc = nbd_establish_connection(s->saddr, &local_err);
+    sioc = nbd_co_establish_connection(s->bs, &local_err);
     if (!sioc) {
         ret = -ECONNREFUSED;
         goto out;
@@ -1946,6 +2208,8 @@ 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);

meson.build

@@ -1095,12 +1095,9 @@ if have_tools
              dependencies: [authz, block, crypto, io, qom, qemuutil], install: true)
   qemu_io = executable('qemu-io', files('qemu-io.c'),
              dependencies: [block, qemuutil], install: true)
-  qemu_block_tools += [qemu_img, qemu_io]
+  qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
-  if targetos != 'windows'
-    qemu_nbd = executable('qemu-nbd', files('qemu-nbd.c'),
                dependencies: [block, qemuutil], install: true)
-    qemu_block_tools += [qemu_nbd]
+  qemu_block_tools += [qemu_img, qemu_io, qemu_nbd]
-  endif
 
   subdir('storage-daemon')
   subdir('contrib/rdmacm-mux')

qemu-img.c

@@ -41,6 +41,7 @@
 #include "qemu/log.h"
 #include "qemu/main-loop.h"
 #include "qemu/module.h"
+#include "qemu/sockets.h"
 #include "qemu/units.h"
 #include "qom/object_interfaces.h"
 #include "sysemu/block-backend.h"
@@ -5410,6 +5411,7 @@ int main(int argc, char **argv)
     signal(SIGPIPE, SIG_IGN);
 #endif
 
+    socket_init();
     error_init(argv[0]);
     module_call_init(MODULE_INIT_TRACE);
     qemu_init_exec_dir(argv[0]);

qemu-io.c

@@ -25,6 +25,7 @@
 #include "qemu/config-file.h"
 #include "qemu/readline.h"
 #include "qemu/log.h"
+#include "qemu/sockets.h"
 #include "qapi/qmp/qstring.h"
 #include "qapi/qmp/qdict.h"
 #include "qom/object_interfaces.h"
@@ -542,6 +543,7 @@ int main(int argc, char **argv)
     signal(SIGPIPE, SIG_IGN);
 #endif
 
+    socket_init();
     error_init(argv[0]);
     module_call_init(MODULE_INIT_TRACE);
     qemu_init_exec_dir(argv[0]);

qemu-nbd.c

@@ -155,12 +155,13 @@ QEMU_COPYRIGHT "\n"
     , name);
 }
 
+#if HAVE_NBD_DEVICE
 static void termsig_handler(int signum)
 {
     atomic_cmpxchg(&state, RUNNING, TERMINATE);
     qemu_notify_event();
 }
-
+#endif /* HAVE_NBD_DEVICE */
 
 static int qemu_nbd_client_list(SocketAddress *saddr, QCryptoTLSCreds *tls,
                                 const char *hostname)
@@ -587,6 +588,7 @@ int main(int argc, char **argv)
     unsigned socket_activation;
     const char *pid_file_name = NULL;
 
+#if HAVE_NBD_DEVICE
     /* The client thread uses SIGTERM to interrupt the server.  A signal
      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
      */
@@ -594,11 +596,13 @@ int main(int argc, char **argv)
     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
     sa_sigterm.sa_handler = termsig_handler;
     sigaction(SIGTERM, &sa_sigterm, NULL);
+#endif /* HAVE_NBD_DEVICE */
 
 #ifdef CONFIG_POSIX
     signal(SIGPIPE, SIG_IGN);
 #endif
 
+    socket_init();
     error_init(argv[0]);
     module_call_init(MODULE_INIT_TRACE);
     qcrypto_init(&error_fatal);
@@ -895,6 +899,7 @@ int main(int argc, char **argv)
 #endif
 
     if ((device && !verbose) || fork_process) {
+#ifndef WIN32
         int stderr_fd[2];
         pid_t pid;
         int ret;
@@ -958,6 +963,10 @@ int main(int argc, char **argv)
              */
             exit(errors);
         }
+#else /* WIN32 */
+        error_report("Unable to fork into background on Windows hosts");
+        exit(EXIT_FAILURE);
+#endif /* WIN32 */
     }
 
     if (device != NULL && sockpath == NULL) {

tests/qemu-iotests/059.out

@@ -19,8 +19,8 @@ file format: IMGFMT
 virtual size: 2 GiB (2147483648 bytes)
 
 === Testing monolithicFlat with zeroed_grain ===
-qemu-img: TEST_DIR/t.IMGFMT: Flat image can't enable zeroed grain
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2147483648
+qemu-img: TEST_DIR/t.IMGFMT: Flat image can't enable zeroed grain
 
 === Testing big twoGbMaxExtentFlat ===
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824000

tests/qemu-iotests/259.out

@@ -10,5 +10,5 @@ disk size: unavailable
 
 --- Testing creation for which the node would need to grow ---
 Formatting 'TEST_DIR/t.IMGFMT', fmt=qcow2 size=67108864 preallocation=metadata
-qemu-img: TEST_DIR/t.IMGFMT: Could not resize image: Image format driver does not support resize
+qemu-img: TEST_DIR/t.IMGFMT: Could not resize image: Cannot grow NBD nodes
 *** done