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https://gitlab.com/qemu-project/qemu
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nbd: keep send_mutex/free_sema handling outside nbd_co_do_establish_connection
Elevate s->in_flight early so that other incoming requests will wait on the CoQueue in nbd_co_send_request; restart them after getting back from nbd_reconnect_attempt. This could be after the reconnect timer or nbd_cancel_in_flight have cancelled the attempt, so there is no need anymore to cancel the requests there. nbd_co_send_request now handles both stopping and restarting pending requests after a successful connection, and there is no need to hold send_mutex in nbd_co_do_establish_connection. The current setup is confusing because nbd_co_do_establish_connection is called both with send_mutex taken and without it. Before the patch it uses free_sema which (at least in theory...) is protected by send_mutex, after the patch it does not anymore. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20220414175756.671165-5-pbonzini@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> [eblake: wrap long line] Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org> Reviewed-by: Lukas Straub <lukasstraub2@web.de> Signed-off-by: Eric Blake <eblake@redhat.com>
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@ -59,7 +59,8 @@ int coroutine_fn bdrv_co_writev_vmstate(BlockDriverState *bs,
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QEMUIOVector *qiov, int64_t pos);
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int coroutine_fn
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nbd_co_do_establish_connection(BlockDriverState *bs, Error **errp);
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nbd_co_do_establish_connection(BlockDriverState *bs, bool blocking,
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Error **errp);
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int coroutine_fn
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@ -109,7 +110,7 @@ bdrv_common_block_status_above(BlockDriverState *bs,
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BlockDriverState **file,
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int *depth);
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int generated_co_wrapper
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nbd_do_establish_connection(BlockDriverState *bs, Error **errp);
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nbd_do_establish_connection(BlockDriverState *bs, bool blocking, Error **errp);
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int generated_co_wrapper
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blk_do_preadv(BlockBackend *blk, int64_t offset, int64_t bytes,
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66
block/nbd.c
66
block/nbd.c
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@ -187,9 +187,6 @@ static void reconnect_delay_timer_cb(void *opaque)
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if (qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTING_WAIT) {
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s->state = NBD_CLIENT_CONNECTING_NOWAIT;
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nbd_co_establish_connection_cancel(s->conn);
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while (qemu_co_enter_next(&s->free_sema, NULL)) {
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/* Resume all queued requests */
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}
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}
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reconnect_delay_timer_del(s);
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@ -310,11 +307,10 @@ static int nbd_handle_updated_info(BlockDriverState *bs, Error **errp)
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}
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int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
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Error **errp)
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bool blocking, Error **errp)
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{
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BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
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int ret;
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bool blocking = nbd_client_connecting_wait(s);
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IO_CODE();
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assert(!s->ioc);
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@ -350,7 +346,6 @@ int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
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/* successfully connected */
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s->state = NBD_CLIENT_CONNECTED;
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qemu_co_queue_restart_all(&s->free_sema);
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return 0;
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}
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@ -358,25 +353,25 @@ int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
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/* called under s->send_mutex */
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static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
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{
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assert(nbd_client_connecting(s));
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assert(s->in_flight == 0);
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if (nbd_client_connecting_wait(s) && s->reconnect_delay &&
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!s->reconnect_delay_timer)
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{
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/*
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* It's first reconnect attempt after switching to
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* NBD_CLIENT_CONNECTING_WAIT
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*/
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reconnect_delay_timer_init(s,
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qemu_clock_get_ns(QEMU_CLOCK_REALTIME) +
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s->reconnect_delay * NANOSECONDS_PER_SECOND);
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}
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bool blocking = nbd_client_connecting_wait(s);
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/*
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* Now we are sure that nobody is accessing the channel, and no one will
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* try until we set the state to CONNECTED.
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*/
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assert(nbd_client_connecting(s));
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assert(s->in_flight == 1);
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if (blocking && !s->reconnect_delay_timer) {
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/*
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* It's the first reconnect attempt after switching to
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* NBD_CLIENT_CONNECTING_WAIT
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*/
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g_assert(s->reconnect_delay);
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reconnect_delay_timer_init(s,
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qemu_clock_get_ns(QEMU_CLOCK_REALTIME) +
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s->reconnect_delay * NANOSECONDS_PER_SECOND);
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}
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/* Finalize previous connection if any */
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if (s->ioc) {
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@ -387,7 +382,9 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
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s->ioc = NULL;
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}
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nbd_co_do_establish_connection(s->bs, NULL);
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qemu_co_mutex_unlock(&s->send_mutex);
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nbd_co_do_establish_connection(s->bs, blocking, NULL);
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qemu_co_mutex_lock(&s->send_mutex);
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/*
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* The reconnect attempt is done (maybe successfully, maybe not), so
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@ -472,21 +469,21 @@ static int coroutine_fn nbd_co_send_request(BlockDriverState *bs,
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qemu_co_mutex_lock(&s->send_mutex);
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while (s->in_flight == MAX_NBD_REQUESTS ||
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(!nbd_client_connected(s) && s->in_flight > 0))
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{
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(!nbd_client_connected(s) && s->in_flight > 0)) {
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qemu_co_queue_wait(&s->free_sema, &s->send_mutex);
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}
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if (nbd_client_connecting(s)) {
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nbd_reconnect_attempt(s);
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}
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if (!nbd_client_connected(s)) {
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rc = -EIO;
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goto err;
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}
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s->in_flight++;
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if (!nbd_client_connected(s)) {
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if (nbd_client_connecting(s)) {
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nbd_reconnect_attempt(s);
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qemu_co_queue_restart_all(&s->free_sema);
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}
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if (!nbd_client_connected(s)) {
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rc = -EIO;
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goto err;
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}
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}
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for (i = 0; i < MAX_NBD_REQUESTS; i++) {
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if (s->requests[i].coroutine == NULL) {
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@ -526,8 +523,8 @@ err:
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nbd_channel_error(s, rc);
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if (i != -1) {
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s->requests[i].coroutine = NULL;
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s->in_flight--;
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}
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s->in_flight--;
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qemu_co_queue_next(&s->free_sema);
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}
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qemu_co_mutex_unlock(&s->send_mutex);
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@ -1882,7 +1879,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
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}
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s->state = NBD_CLIENT_CONNECTING_WAIT;
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ret = nbd_do_establish_connection(bs, errp);
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ret = nbd_do_establish_connection(bs, true, errp);
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if (ret < 0) {
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goto fail;
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}
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@ -2048,7 +2045,6 @@ static void nbd_cancel_in_flight(BlockDriverState *bs)
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if (s->state == NBD_CLIENT_CONNECTING_WAIT) {
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s->state = NBD_CLIENT_CONNECTING_NOWAIT;
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qemu_co_queue_restart_all(&s->free_sema);
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}
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nbd_co_establish_connection_cancel(s->conn);
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