[PATCH v3 5/6] nbd: Refactor counting of meta contexts

[Eric Blake <eblake@redhat.com>]

Rather than open-code the count of negotiated contexts at several
sites, embed it directly into the struct.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 nbd/server.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/nbd/server.c b/nbd/server.c
index 6326d6fe3f3a..3664f9e744b4 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -106,8 +106,7 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  * NBD_OPT_LIST_META_CONTEXT. */
 typedef struct NBDExportMetaContexts {
     NBDExport *exp;
-    bool valid; /* means that negotiation of the option finished without
-                   errors */
+    size_t count; /* number of negotiated contexts */
     bool base_allocation; /* export base:allocation context (block status) */
     bool allocation_depth; /* export qemu:allocation-depth */
     bool bitmap; /* export qemu:dirty-bitmap:<export bitmap name> */
@@ -448,7 +447,9 @@ static int nbd_negotiate_handle_list(NBDClient *client, Error **errp)

 static void nbd_check_meta_export(NBDClient *client)
 {
-    client->export_meta.valid &= client->exp == client->export_meta.exp;
+    if (client->exp != client->export_meta.exp) {
+        client->export_meta.count = 0;
+    }
 }

 /* Send a reply to NBD_OPT_EXPORT_NAME.
@@ -956,6 +957,7 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
     NBDExportMetaContexts local_meta;
     uint32_t nb_queries;
     int i;
+    size_t count = 0;

     if (!client->structured_reply) {
         return nbd_opt_invalid(client, errp,
@@ -1013,6 +1015,7 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
         if (ret < 0) {
             return ret;
         }
+        count++;
     }

     if (meta->allocation_depth) {
@@ -1022,6 +1025,7 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
         if (ret < 0) {
             return ret;
         }
+        count++;
     }

     if (meta->bitmap) {
@@ -1035,11 +1039,12 @@ static int nbd_negotiate_meta_queries(NBDClient *client,
         if (ret < 0) {
             return ret;
         }
+        count++;
     }

     ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
     if (ret == 0) {
-        meta->valid = true;
+        meta->count = count;
     }

     return ret;
@@ -2400,15 +2405,9 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
             return nbd_send_generic_reply(client, request->handle, -EINVAL,
                                           "need non-zero length", errp);
         }
-        if (client->export_meta.valid &&
-            (client->export_meta.base_allocation ||
-             client->export_meta.allocation_depth ||
-             client->export_meta.bitmap))
-        {
+        if (client->export_meta.count) {
             bool dont_fragment = request->flags & NBD_CMD_FLAG_REQ_ONE;
-            int contexts_remaining = client->export_meta.base_allocation +
-                client->export_meta.allocation_depth +
-                client->export_meta.bitmap;
+            int contexts_remaining = client->export_meta.count;

             if (client->export_meta.base_allocation) {
                 ret = nbd_co_send_block_status(client, request->handle,
-- 
2.28.0