mxqd: Simplify start_user

Historically, start_user was called with differenct values for the
job_limit argument. Jobs were started round-robin from the groups with
highest priority round-robin. If no more jobs could be started from that
priority, jobs from lower priority were considered, too.

The groups are ordered by priority.

Currently, start_user is always called with a job_limit argument of 1
and just the first eligible jobs is started.

Remove the job_limit argument and start a single job only.  Remove the
code complexity which is no longer needed.

mxqd.c

@@ -1273,18 +1273,12 @@ unsigned long start_job(struct mxq_group_list *glist)
 
 /**********************************************************************/
 
-unsigned long start_user(struct mxq_user_list *ulist, int job_limit, long slots_to_start)
+unsigned long start_user(struct mxq_user_list *ulist, long slots_to_start)
 {
     struct mxq_server *server;
     struct mxq_group_list *glist;
-    struct mxq_group_list *gnext = NULL;
     struct mxq_group *group;
 
-    unsigned int prio;
-    unsigned char started = 0;
-    unsigned long slots_started = 0;
-    int jobs_started = 0;
-
     unsigned long df_scratch;
 
     assert(ulist);
@@ -1295,67 +1289,42 @@ unsigned long start_user(struct mxq_user_list *ulist, int job_limit, long slots_
     glist  = ulist->groups;
     group  = &glist->group;
 
-    prio = group->group_priority;
-
     assert(slots_to_start <= server->slots - server->slots_running);
 
-    mx_log_debug(" user=%s(%d) slots_to_start=%ld job_limit=%d :: trying to start jobs for user.",
-            group->user_name, group->user_uid, slots_to_start, job_limit);
+    mx_log_debug(" user=%s(%d) slots_to_start=%ld :: trying to start jobs for user.",
+            group->user_name, group->user_uid, slots_to_start);
 
     df_scratch=mx_df(MXQ_JOB_TMPDIR_FS "/.");
 
-    for (glist = ulist->groups; glist && slots_to_start > 0 && (!job_limit || jobs_started < job_limit); glist = gnext) {
+    for (glist = ulist->groups; glist ; glist = glist->next) {
 
         group  = &glist->group;
-        gnext  = glist->next;
-
-        assert(glist->jobs_running <= group->group_jobs);
-        assert(glist->jobs_running <= glist->jobs_max);
 
         if (glist->jobs_running == group->group_jobs) {
-            goto start_user_continue;
+            continue;
         }
         if (glist->jobs_running == glist->jobs_max) {
-            goto start_user_continue;
+            continue;
         }
         if (mxq_group_jobs_inq(group) == 0) {
-            goto start_user_continue;
+            continue;
         }
         if (glist->slots_per_job > slots_to_start) {
-            goto start_user_continue;
+            continue;
         }
-
         if (df_scratch/1024/1024/1024 < group->job_tmpdir_size + 20) {
-            goto start_user_continue;
+            continue;
         }
 
-        if (group->group_priority < prio) {
-            if (started) {
-                goto start_user_rewind;
-            }
-            prio = group->group_priority;
-        }
         mx_log_info("  group=%s(%d):%lu slots_to_start=%ld slots_per_job=%lu :: trying to start job for group.",
                 group->user_name, group->user_uid, group->group_id, slots_to_start, glist->slots_per_job);
 
         if (start_job(glist)) {
-            slots_to_start -= glist->slots_per_job;
-            jobs_started++;
-            slots_started += glist->slots_per_job;
-
-            started = 1;
+            int slots_started = glist->slots_per_job;
+            return slots_started;
         }
-
-start_user_continue:
-        if (gnext || !started)
-            continue;
-
-start_user_rewind:
-        gnext = ulist->groups;
-        started = 0;
-        continue;
     }
-    return slots_started;
+    return 0;
 }
 
 /**********************************************************************/
@@ -1390,7 +1359,7 @@ long start_user_with_least_running_global_slot_count(struct mxq_server *server)
         if (waiting && ulist->global_slots_running > global_slots_per_user)
             return -1;
 
-        slots_started = start_user(ulist, 1, slots_free);
+        slots_started = start_user(ulist, slots_free);
         if (slots_started)
             return slots_started;