block: Decouple throttling from BlockDriverState

This moves the throttling related part of the BDS life cycle management
to BlockBackend. The throttling group reference is now kept even when no
medium is inserted.

With this commit, throttling isn't disabled and then re-enabled any more
during graph reconfiguration. This fixes the temporary breakage of I/O
throttling when used with live snapshots or block jobs that manipulate
the graph.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 14 insertions, 23 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 74429ae36b..a71b54d24d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -188,10 +188,6 @@ static void blk_delete(BlockBackend *blk)
     }
     assert(QLIST_EMPTY(&blk->remove_bs_notifiers.notifiers));
     assert(QLIST_EMPTY(&blk->insert_bs_notifiers.notifiers));
-    if (blk->root_state.throttle_state) {
-        g_free(blk->root_state.throttle_group);
-        throttle_group_unref(blk->root_state.throttle_state);
-    }
     QTAILQ_REMOVE(&block_backends, blk, link);
     drive_info_del(blk->legacy_dinfo);
     block_acct_cleanup(&blk->stats);
@@ -445,12 +441,12 @@ void blk_remove_bs(BlockBackend *blk)
     assert(blk->root->bs->blk == blk);
 
     notifier_list_notify(&blk->remove_bs_notifiers, blk);
-
-    blk_update_root_state(blk);
     if (blk->public.throttle_state) {
-        blk_io_limits_disable(blk);
+        throttle_timers_detach_aio_context(&blk->public.throttle_timers);
     }
 
+    blk_update_root_state(blk);
+
     blk->root->bs->blk = NULL;
     bdrv_root_unref_child(blk->root);
     blk->root = NULL;
@@ -468,6 +464,10 @@ void blk_insert_bs(BlockBackend *blk, BlockDriverState *bs)
     bs->blk = blk;
 
     notifier_list_notify(&blk->insert_bs_notifiers, blk);
+    if (blk->public.throttle_state) {
+        throttle_timers_attach_aio_context(
+            &blk->public.throttle_timers, bdrv_get_aio_context(bs));
+    }
 }
 
 /*
@@ -1374,7 +1374,14 @@ void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
     BlockDriverState *bs = blk_bs(blk);
 
     if (bs) {
+        if (blk->public.throttle_state) {
+            throttle_timers_detach_aio_context(&blk->public.throttle_timers);
+        }
         bdrv_set_aio_context(bs, new_context);
+        if (blk->public.throttle_state) {
+            throttle_timers_attach_aio_context(&blk->public.throttle_timers,
+                                               new_context);
+        }
     }
 }
 
@@ -1539,19 +1546,6 @@ void blk_update_root_state(BlockBackend *blk)
     blk->root_state.open_flags    = blk->root->bs->open_flags;
     blk->root_state.read_only     = blk->root->bs->read_only;
     blk->root_state.detect_zeroes = blk->root->bs->detect_zeroes;
-
-    if (blk->root_state.throttle_group) {
-        g_free(blk->root_state.throttle_group);
-        throttle_group_unref(blk->root_state.throttle_state);
-    }
-    if (blk->public.throttle_state) {
-        const char *name = throttle_group_get_name(blk);
-        blk->root_state.throttle_group = g_strdup(name);
-        blk->root_state.throttle_state = throttle_group_incref(name);
-    } else {
-        blk->root_state.throttle_group = NULL;
-        blk->root_state.throttle_state = NULL;
-    }
 }
 
 /*
@@ -1562,9 +1556,6 @@ void blk_update_root_state(BlockBackend *blk)
 void blk_apply_root_state(BlockBackend *blk, BlockDriverState *bs)
 {
     bs->detect_zeroes = blk->root_state.detect_zeroes;
-    if (blk->root_state.throttle_group) {
-        blk_io_limits_enable(blk, blk->root_state.throttle_group);
-    }
 }
 
 /*