block/nbd: split nbd_handle_updated_info out of nbd_client_handshake()

To be reused in the following patch.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210610100802.5888-23-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

block/nbd.c

@@ -314,6 +314,51 @@ static bool nbd_client_connecting_wait(BDRVNBDState *s)
     return qatomic_load_acquire(&s->state) == NBD_CLIENT_CONNECTING_WAIT;
 }
 
+/*
+ * Update @bs with information learned during a completed negotiation process.
+ * Return failure if the server's advertised options are incompatible with the
+ * client's needs.
+ */
+static int nbd_handle_updated_info(BlockDriverState *bs, Error **errp)
+{
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+    int ret;
+
+    if (s->x_dirty_bitmap) {
+        if (!s->info.base_allocation) {
+            error_setg(errp, "requested x-dirty-bitmap %s not found",
+                       s->x_dirty_bitmap);
+            return -EINVAL;
+        }
+        if (strcmp(s->x_dirty_bitmap, "qemu:allocation-depth") == 0) {
+            s->alloc_depth = true;
+        }
+    }
+
+    if (s->info.flags & NBD_FLAG_READ_ONLY) {
+        ret = bdrv_apply_auto_read_only(bs, "NBD export is read-only", errp);
+        if (ret < 0) {
+            return ret;
+        }
+    }
+
+    if (s->info.flags & NBD_FLAG_SEND_FUA) {
+        bs->supported_write_flags = BDRV_REQ_FUA;
+        bs->supported_zero_flags |= BDRV_REQ_FUA;
+    }
+
+    if (s->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
+        bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
+        if (s->info.flags & NBD_FLAG_SEND_FAST_ZERO) {
+            bs->supported_zero_flags |= BDRV_REQ_NO_FALLBACK;
+        }
+    }
+
+    trace_nbd_client_handshake_success(s->export);
+
+    return 0;
+}
+
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
 {
     int ret;
@@ -1575,49 +1620,13 @@ static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
         s->sioc = NULL;
         return ret;
     }
-    if (s->x_dirty_bitmap) {
-        if (!s->info.base_allocation) {
-            error_setg(errp, "requested x-dirty-bitmap %s not found",
-                       s->x_dirty_bitmap);
-            ret = -EINVAL;
-            goto fail;
-        }
-        if (strcmp(s->x_dirty_bitmap, "qemu:allocation-depth") == 0) {
-            s->alloc_depth = true;
-        }
-    }
-    if (s->info.flags & NBD_FLAG_READ_ONLY) {
-        ret = bdrv_apply_auto_read_only(bs, "NBD export is read-only", errp);
-        if (ret < 0) {
-            goto fail;
-        }
-    }
-    if (s->info.flags & NBD_FLAG_SEND_FUA) {
-        bs->supported_write_flags = BDRV_REQ_FUA;
-        bs->supported_zero_flags |= BDRV_REQ_FUA;
-    }
-    if (s->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
-        bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
-        if (s->info.flags & NBD_FLAG_SEND_FAST_ZERO) {
-            bs->supported_zero_flags |= BDRV_REQ_NO_FALLBACK;
-        }
-    }
 
-    if (!s->ioc) {
-        s->ioc = QIO_CHANNEL(s->sioc);
-        object_ref(OBJECT(s->ioc));
-    }
-
-    trace_nbd_client_handshake_success(s->export);
-
-    return 0;
-
- fail:
-    /*
-     * We have connected, but must fail for other reasons.
-     * Send NBD_CMD_DISC as a courtesy to the server.
-     */
-    {
+    ret = nbd_handle_updated_info(bs, errp);
+    if (ret < 0) {
+        /*
+         * We have connected, but must fail for other reasons.
+         * Send NBD_CMD_DISC as a courtesy to the server.
+         */
         NBDRequest request = { .type = NBD_CMD_DISC };
 
         nbd_send_request(s->ioc ?: QIO_CHANNEL(s->sioc), &request);
@@ -1631,6 +1640,13 @@ static int nbd_client_handshake(BlockDriverState *bs, Error **errp)
 
         return ret;
     }
+
+    if (!s->ioc) {
+        s->ioc = QIO_CHANNEL(s->sioc);
+        object_ref(OBJECT(s->ioc));
+    }
+
+    return 0;
 }
 
 /*