[PULL 6/9] block/nbd: split nbd_establish_connection out of nbd_client_connect

[Eric Blake <eblake@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

We are going to implement non-blocking version of
nbd_establish_connection, which for a while will be used only for
nbd_reconnect_attempt, not for nbd_open, so we need to call it
separately.

Refactor nbd_reconnect_attempt in a way which makes next commit
simpler.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200727184751.15704-2-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/nbd.c        | 60 +++++++++++++++++++++++++++-------------------
 block/trace-events |  4 ++--
 2 files changed, 38 insertions(+), 26 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 8934bcb47901..3558c173e34b 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -93,7 +93,10 @@ typedef struct BDRVNBDState {
     char *x_dirty_bitmap;
 } BDRVNBDState;

-static int nbd_client_connect(BlockDriverState *bs, Error **errp);
+static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
+                                                  Error **errp);
+static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
+                                Error **errp);

 static void nbd_clear_bdrvstate(BDRVNBDState *s)
 {
@@ -241,7 +244,9 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)

 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
+    int ret;
     Error *local_err = NULL;
+    QIOChannelSocket *sioc;

     if (!nbd_client_connecting(s)) {
         return;
@@ -280,19 +285,25 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
         s->ioc = NULL;
     }

-    s->connect_status = nbd_client_connect(s->bs, &local_err);
+    sioc = nbd_establish_connection(s->saddr, &local_err);
+    if (!sioc) {
+        ret = -ECONNREFUSED;
+        goto out;
+    }
+
+    ret = nbd_client_handshake(s->bs, sioc, &local_err);
+
+out:
+    s->connect_status = ret;
     error_free(s->connect_err);
     s->connect_err = NULL;
     error_propagate(&s->connect_err, local_err);

-    if (s->connect_status < 0) {
-        /* failed attempt */
-        return;
+    if (ret >= 0) {
+        /* successfully connected */
+        s->state = NBD_CLIENT_CONNECTED;
+        qemu_co_queue_restart_all(&s->free_sema);
     }
-
-    /* successfully connected */
-    s->state = NBD_CLIENT_CONNECTED;
-    qemu_co_queue_restart_all(&s->free_sema);
 }

 static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState *s)
@@ -1425,24 +1436,15 @@ static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
     return sioc;
 }

-static int nbd_client_connect(BlockDriverState *bs, Error **errp)
+/* nbd_client_handshake takes ownership on sioc. On failure it is unref'ed. */
+static int nbd_client_handshake(BlockDriverState *bs, QIOChannelSocket *sioc,
+                                Error **errp)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     AioContext *aio_context = bdrv_get_aio_context(bs);
     int ret;

-    /*
-     * establish TCP connection, return error if it fails
-     * TODO: Configurable retry-until-timeout behaviour.
-     */
-    QIOChannelSocket *sioc = nbd_establish_connection(s->saddr, errp);
-
-    if (!sioc) {
-        return -ECONNREFUSED;
-    }
-
-    /* NBD handshake */
-    trace_nbd_client_connect(s->export);
+    trace_nbd_client_handshake(s->export);
     qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
     qio_channel_attach_aio_context(QIO_CHANNEL(sioc), aio_context);

@@ -1489,7 +1491,7 @@ static int nbd_client_connect(BlockDriverState *bs, Error **errp)
         object_ref(OBJECT(s->ioc));
     }

-    trace_nbd_client_connect_success(s->export);
+    trace_nbd_client_handshake_success(s->export);

     return 0;

@@ -1894,6 +1896,7 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
 {
     int ret;
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    QIOChannelSocket *sioc;

     ret = nbd_process_options(bs, options, errp);
     if (ret < 0) {
@@ -1904,7 +1907,16 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     qemu_co_mutex_init(&s->send_mutex);
     qemu_co_queue_init(&s->free_sema);

-    ret = nbd_client_connect(bs, errp);
+    /*
+     * establish TCP connection, return error if it fails
+     * TODO: Configurable retry-until-timeout behaviour.
+     */
+    sioc = nbd_establish_connection(s->saddr, errp);
+    if (!sioc) {
+        return -ECONNREFUSED;
+    }
+
+    ret = nbd_client_handshake(bs, sioc, errp);
     if (ret < 0) {
         nbd_clear_bdrvstate(s);
         return ret;
diff --git a/block/trace-events b/block/trace-events
index d3533ca8963c..915833506189 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -168,8 +168,8 @@ nbd_parse_blockstatus_compliance(const char *err) "ignoring extra data from non-
 nbd_structured_read_compliance(const char *type) "server sent non-compliant unaligned read %s chunk"
 nbd_read_reply_entry_fail(int ret, const char *err) "ret = %d, err: %s"
 nbd_co_request_fail(uint64_t from, uint32_t len, uint64_t handle, uint16_t flags, uint16_t type, const char *name, int ret, const char *err) "Request failed { .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) } ret = %d, err: %s"
-nbd_client_connect(const char *export_name) "export '%s'"
-nbd_client_connect_success(const char *export_name) "export '%s'"
+nbd_client_handshake(const char *export_name) "export '%s'"
+nbd_client_handshake_success(const char *export_name) "export '%s'"

 # ssh.c
 ssh_restart_coroutine(void *co) "co=%p"
-- 
2.27.0