monitor: Allow add-fd to any specified fd set

The first call to add an fd to an fd set was previously not
allowed to choose the fd set ID.  The ID was generated as
the first available and ensuing calls could add more fds by
specifying the fd set ID.  This change allows users to
choose the fd set ID on the first call.
Signed-off-by: NCorey Bryant <coreyb@linux.vnet.ibm.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

monitor.c

@@ -2135,7 +2135,7 @@ AddfdInfo *qmp_add_fd(bool has_fdset_id, int64_t fdset_id, bool has_opaque,
 {
     int fd;
     Monitor *mon = cur_mon;
-    MonFdset *mon_fdset;
+    MonFdset *mon_fdset = NULL;
     MonFdsetFd *mon_fdset_fd;
     AddfdInfo *fdinfo;
 
@@ -2147,34 +2147,54 @@ AddfdInfo *qmp_add_fd(bool has_fdset_id, int64_t fdset_id, bool has_opaque,
 
     if (has_fdset_id) {
         QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
-            if (mon_fdset->id == fdset_id) {
+            /* Break if match found or match impossible due to ordering by ID */
+            if (fdset_id <= mon_fdset->id) {
+                if (fdset_id < mon_fdset->id) {
+                    mon_fdset = NULL;
+                }
                 break;
             }
         }
-        if (mon_fdset == NULL) {
-            error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdset-id",
-                      "an existing fdset-id");
-            goto error;
-        }
-    } else {
+    }
+
+    if (mon_fdset == NULL) {
         int64_t fdset_id_prev = -1;
         MonFdset *mon_fdset_cur = QLIST_FIRST(&mon_fdsets);
 
-        /* Use first available fdset ID */
-        QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
-            mon_fdset_cur = mon_fdset;
-            if (fdset_id_prev == mon_fdset_cur->id - 1) {
-                fdset_id_prev = mon_fdset_cur->id;
-                continue;
+        if (has_fdset_id) {
+            if (fdset_id < 0) {
+                error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdset-id",
+                          "a non-negative value");
+                goto error;
+            }
+            /* Use specified fdset ID */
+            QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
+                mon_fdset_cur = mon_fdset;
+                if (fdset_id < mon_fdset_cur->id) {
+                    break;
+                }
+            }
+        } else {
+            /* Use first available fdset ID */
+            QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
+                mon_fdset_cur = mon_fdset;
+                if (fdset_id_prev == mon_fdset_cur->id - 1) {
+                    fdset_id_prev = mon_fdset_cur->id;
+                    continue;
+                }
+                break;
             }
-            break;
         }
 
         mon_fdset = g_malloc0(sizeof(*mon_fdset));
-        mon_fdset->id = fdset_id_prev + 1;
+        if (has_fdset_id) {
+            mon_fdset->id = fdset_id;
+        } else {
+            mon_fdset->id = fdset_id_prev + 1;
+        }
 
         /* The fdset list is ordered by fdset ID */
-        if (mon_fdset->id == 0) {
+        if (!mon_fdset_cur) {
             QLIST_INSERT_HEAD(&mon_fdsets, mon_fdset, next);
         } else if (mon_fdset->id < mon_fdset_cur->id) {
             QLIST_INSERT_BEFORE(mon_fdset_cur, mon_fdset, next);

qapi-schema.json

@@ -2625,7 +2625,7 @@
 #
 # Returns: @AddfdInfo on success
 #          If file descriptor was not received, FdNotSupplied
-#          If @fdset-id does not exist, InvalidParameterValue
+#          If @fdset-id is a negative value, InvalidParameterValue
 #
 # Notes: The list of fd sets is shared by all monitor connections.
 #