block: remove timer canceling in throttle_config()

throttle_config() cancels the timers of the calling BlockBackend. This
doesn't make sense because other BlockBackends in the group remain
untouched. There's no need to cancel the timers in the one specific
BlockBackend so let's not do that. Throttled requests will run as
scheduled and future requests will follow the new configuration. This
also allows a throttle group's configuration to be changed even when it
has no members.

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/throttle-groups.c

@@ -426,18 +426,10 @@ void throttle_group_restart_blk(BlockBackend *blk)
 void throttle_group_config(BlockBackend *blk, ThrottleConfig *cfg)
 {
     BlockBackendPublic *blkp = blk_get_public(blk);
-    ThrottleTimers *tt = &blkp->throttle_timers;
     ThrottleState *ts = blkp->throttle_state;
     ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
     qemu_mutex_lock(&tg->lock);
-    /* throttle_config() cancels the timers */
-    if (timer_pending(tt->timers[0])) {
-        tg->any_timer_armed[0] = false;
-    }
-    if (timer_pending(tt->timers[1])) {
-        tg->any_timer_armed[1] = false;
-    }
-    throttle_config(ts, tg->clock_type, tt, cfg);
+    throttle_config(ts, tg->clock_type, cfg);
     qemu_mutex_unlock(&tg->lock);
 
     throttle_group_restart_blk(blk);

fsdev/qemu-fsdev-throttle.c

@@ -86,7 +86,7 @@ void fsdev_throttle_init(FsThrottle *fst)
                              fsdev_throttle_read_timer_cb,
                              fsdev_throttle_write_timer_cb,
                              fst);
-        throttle_config(&fst->ts, QEMU_CLOCK_REALTIME, &fst->tt, &fst->cfg);
+        throttle_config(&fst->ts, QEMU_CLOCK_REALTIME, &fst->cfg);
         qemu_co_queue_init(&fst->throttled_reqs[0]);
         qemu_co_queue_init(&fst->throttled_reqs[1]);
     }

include/qemu/throttle.h

@@ -140,7 +140,6 @@ bool throttle_is_valid(ThrottleConfig *cfg, Error **errp);
 
 void throttle_config(ThrottleState *ts,
                      QEMUClockType clock_type,
-                     ThrottleTimers *tt,
                      ThrottleConfig *cfg);
 
 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);

tests/test-throttle.c

@@ -228,7 +228,7 @@ static void test_config_functions(void)
                          read_timer_cb, write_timer_cb, &ts);
     /* structure reset by throttle_init previous_leak should be null */
     g_assert(!ts.previous_leak);
-    throttle_config(&ts, QEMU_CLOCK_VIRTUAL, &tt, &orig_cfg);
+    throttle_config(&ts, QEMU_CLOCK_VIRTUAL, &orig_cfg);
 
     /* has previous leak been initialized by throttle_config ? */
     g_assert(ts.previous_leak);
@@ -486,7 +486,7 @@ static bool do_test_accounting(bool is_ops, /* are we testing bps or ops */
     throttle_init(&ts);
     throttle_timers_init(&tt, ctx, QEMU_CLOCK_VIRTUAL,
                          read_timer_cb, write_timer_cb, &ts);
-    throttle_config(&ts, QEMU_CLOCK_VIRTUAL, &tt, &cfg);
+    throttle_config(&ts, QEMU_CLOCK_VIRTUAL, &cfg);
 
     /* account a read */
     throttle_account(&ts, false, size);

util/throttle.c

@@ -388,24 +388,14 @@ static void throttle_unfix_bucket(LeakyBucket *bkt)
     }
 }
 
-/* take care of canceling a timer */
-static void throttle_cancel_timer(QEMUTimer *timer)
-{
-    assert(timer != NULL);
-
-    timer_del(timer);
-}
-
 /* Used to configure the throttle
  *
  * @ts: the throttle state we are working on
  * @clock_type: the group's clock_type
- * @tt: the throttle timers we use in this aio context
  * @cfg: the config to set
  */
 void throttle_config(ThrottleState *ts,
                      QEMUClockType clock_type,
-                     ThrottleTimers *tt,
                      ThrottleConfig *cfg)
 {
     int i;
@@ -417,10 +407,6 @@ void throttle_config(ThrottleState *ts,
     }
 
     ts->previous_leak = qemu_clock_get_ns(clock_type);
-
-    for (i = 0; i < 2; i++) {
-        throttle_cancel_timer(tt->timers[i]);
-    }
 }
 
 /* used to get config