qemu-kvm/kvm-block-Remove-subtree-drains.patch

From 79063522861cb2baf921b204bcdf4c3bfb5697f4 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 18 Nov 2022 18:41:05 +0100
Subject: [PATCH 23/31] block: Remove subtree drains

RH-Author: Stefano Garzarella <sgarzare@redhat.com>
RH-MergeRequest: 135: block: Simplify drain to prevent QEMU from crashing during snapshot
RH-Bugzilla: 2155112
RH-Acked-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Commit: [11/16] d92f5041cceeeec49a65441b22d20f692c0f1c77 (sgarzarella/qemu-kvm-c-9-s)

Subtree drains are not used any more. Remove them.

After this, BdrvChildClass.attach/detach() don't poll any more.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221118174110.55183-11-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 299403aedaeb7f08d8e98aa8614b29d4e5546066)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 block.c                          |  20 +--
 block/io.c                       | 121 +++-----------
 include/block/block-io.h         |  18 +--
 include/block/block_int-common.h |   1 -
 include/block/block_int-io.h     |  12 --
 tests/unit/test-bdrv-drain.c     | 261 ++-----------------------------
 6 files changed, 44 insertions(+), 389 deletions(-)

diff --git a/block.c b/block.c
index 5330e89903..e0e3b21790 100644
--- a/block.c
+++ b/block.c
@@ -1232,7 +1232,7 @@ static void bdrv_child_cb_drained_begin(BdrvChild *child)
 static bool bdrv_child_cb_drained_poll(BdrvChild *child)
 {
     BlockDriverState *bs = child->opaque;
-    return bdrv_drain_poll(bs, false, NULL, false);
+    return bdrv_drain_poll(bs, NULL, false);
 }
 
 static void bdrv_child_cb_drained_end(BdrvChild *child)
@@ -1482,8 +1482,6 @@ static void bdrv_child_cb_attach(BdrvChild *child)
         assert(!bs->file);
         bs->file = child;
     }
-
-    bdrv_apply_subtree_drain(child, bs);
 }
 
 static void bdrv_child_cb_detach(BdrvChild *child)
@@ -1494,8 +1492,6 @@ static void bdrv_child_cb_detach(BdrvChild *child)
         bdrv_backing_detach(child);
     }
 
-    bdrv_unapply_subtree_drain(child, bs);
-
     assert_bdrv_graph_writable(bs);
     QLIST_REMOVE(child, next);
     if (child == bs->backing) {
@@ -2851,9 +2847,6 @@ static void bdrv_replace_child_noperm(BdrvChild *child,
     }
 
     if (old_bs) {
-        /* Detach first so that the recursive drain sections coming from @child
-         * are already gone and we only end the drain sections that came from
-         * elsewhere. */
         if (child->klass->detach) {
             child->klass->detach(child);
         }
@@ -2868,17 +2861,14 @@ static void bdrv_replace_child_noperm(BdrvChild *child,
         QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent);
 
         /*
-         * Detaching the old node may have led to the new node's
-         * quiesce_counter having been decreased.  Not a problem, we
-         * just need to recognize this here and then invoke
-         * drained_end appropriately more often.
+         * Polling in bdrv_parent_drained_begin_single() may have led to the new
+         * node's quiesce_counter having been decreased.  Not a problem, we just
+         * need to recognize this here and then invoke drained_end appropriately
+         * more often.
          */
         assert(new_bs->quiesce_counter <= new_bs_quiesce_counter);
         drain_saldo += new_bs->quiesce_counter - new_bs_quiesce_counter;
 
-        /* Attach only after starting new drained sections, so that recursive
-         * drain sections coming from @child don't get an extra .drained_begin
-         * callback. */
         if (child->klass->attach) {
             child->klass->attach(child);
         }
diff --git a/block/io.c b/block/io.c
index a25103be6f..75224480d0 100644
--- a/block/io.c
+++ b/block/io.c
@@ -236,17 +236,15 @@ typedef struct {
     BlockDriverState *bs;
     bool done;
     bool begin;
-    bool recursive;
     bool poll;
     BdrvChild *parent;
     bool ignore_bds_parents;
 } BdrvCoDrainData;
 
 /* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */
-bool bdrv_drain_poll(BlockDriverState *bs, bool recursive,
-                     BdrvChild *ignore_parent, bool ignore_bds_parents)
+bool bdrv_drain_poll(BlockDriverState *bs, BdrvChild *ignore_parent,
+                     bool ignore_bds_parents)
 {
-    BdrvChild *child, *next;
     IO_OR_GS_CODE();
 
     if (bdrv_parent_drained_poll(bs, ignore_parent, ignore_bds_parents)) {
@@ -257,29 +255,19 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive,
         return true;
     }
 
-    if (recursive) {
-        assert(!ignore_bds_parents);
-        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
-            if (bdrv_drain_poll(child->bs, recursive, child, false)) {
-                return true;
-            }
-        }
-    }
-
     return false;
 }
 
-static bool bdrv_drain_poll_top_level(BlockDriverState *bs, bool recursive,
+static bool bdrv_drain_poll_top_level(BlockDriverState *bs,
                                       BdrvChild *ignore_parent)
 {
-    return bdrv_drain_poll(bs, recursive, ignore_parent, false);
+    return bdrv_drain_poll(bs, ignore_parent, false);
 }
 
-static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
-                                  BdrvChild *parent, bool ignore_bds_parents,
-                                  bool poll);
-static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive,
-                                BdrvChild *parent, bool ignore_bds_parents);
+static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
+                                  bool ignore_bds_parents, bool poll);
+static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent,
+                                bool ignore_bds_parents);
 
 static void bdrv_co_drain_bh_cb(void *opaque)
 {
@@ -292,12 +280,11 @@ static void bdrv_co_drain_bh_cb(void *opaque)
         aio_context_acquire(ctx);
         bdrv_dec_in_flight(bs);
         if (data->begin) {
-            bdrv_do_drained_begin(bs, data->recursive, data->parent,
-                                  data->ignore_bds_parents, data->poll);
+            bdrv_do_drained_begin(bs, data->parent, data->ignore_bds_parents,
+                                  data->poll);
         } else {
             assert(!data->poll);
-            bdrv_do_drained_end(bs, data->recursive, data->parent,
-                                data->ignore_bds_parents);
+            bdrv_do_drained_end(bs, data->parent, data->ignore_bds_parents);
         }
         aio_context_release(ctx);
     } else {
@@ -310,7 +297,7 @@ static void bdrv_co_drain_bh_cb(void *opaque)
 }
 
 static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
-                                                bool begin, bool recursive,
+                                                bool begin,
                                                 BdrvChild *parent,
                                                 bool ignore_bds_parents,
                                                 bool poll)
@@ -329,7 +316,6 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
         .bs = bs,
         .done = false,
         .begin = begin,
-        .recursive = recursive,
         .parent = parent,
         .ignore_bds_parents = ignore_bds_parents,
         .poll = poll,
@@ -380,29 +366,16 @@ void bdrv_do_drained_begin_quiesce(BlockDriverState *bs,
     }
 }
 
-static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
-                                  BdrvChild *parent, bool ignore_bds_parents,
-                                  bool poll)
+static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
+                                  bool ignore_bds_parents, bool poll)
 {
-    BdrvChild *child, *next;
-
     if (qemu_in_coroutine()) {
-        bdrv_co_yield_to_drain(bs, true, recursive, parent, ignore_bds_parents,
-                               poll);
+        bdrv_co_yield_to_drain(bs, true, parent, ignore_bds_parents, poll);
         return;
     }
 
     bdrv_do_drained_begin_quiesce(bs, parent, ignore_bds_parents);
 
-    if (recursive) {
-        assert(!ignore_bds_parents);
-        bs->recursive_quiesce_counter++;
-        QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
-            bdrv_do_drained_begin(child->bs, true, child, ignore_bds_parents,
-                                  false);
-        }
-    }
-
     /*
      * Wait for drained requests to finish.
      *
@@ -414,35 +387,27 @@ static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,
      */
     if (poll) {
         assert(!ignore_bds_parents);
-        BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, recursive, parent));
+        BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
     }
 }
 
 void bdrv_drained_begin(BlockDriverState *bs)
 {
     IO_OR_GS_CODE();
-    bdrv_do_drained_begin(bs, false, NULL, false, true);
-}
-
-void bdrv_subtree_drained_begin(BlockDriverState *bs)
-{
-    IO_OR_GS_CODE();
-    bdrv_do_drained_begin(bs, true, NULL, false, true);
+    bdrv_do_drained_begin(bs, NULL, false, true);
 }
 
 /**
  * This function does not poll, nor must any of its recursively called
  * functions.
  */
-static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive,
-                                BdrvChild *parent, bool ignore_bds_parents)
+static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent,
+                                bool ignore_bds_parents)
 {
-    BdrvChild *child;
     int old_quiesce_counter;
 
     if (qemu_in_coroutine()) {
-        bdrv_co_yield_to_drain(bs, false, recursive, parent, ignore_bds_parents,
-                               false);
+        bdrv_co_yield_to_drain(bs, false, parent, ignore_bds_parents, false);
         return;
     }
     assert(bs->quiesce_counter > 0);
@@ -457,46 +422,12 @@ static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive,
     if (old_quiesce_counter == 1) {
         aio_enable_external(bdrv_get_aio_context(bs));
     }
-
-    if (recursive) {
-        assert(!ignore_bds_parents);
-        bs->recursive_quiesce_counter--;
-        QLIST_FOREACH(child, &bs->children, next) {
-            bdrv_do_drained_end(child->bs, true, child, ignore_bds_parents);
-        }
-    }
 }
 
 void bdrv_drained_end(BlockDriverState *bs)
 {
     IO_OR_GS_CODE();
-    bdrv_do_drained_end(bs, false, NULL, false);
-}
-
-void bdrv_subtree_drained_end(BlockDriverState *bs)
-{
-    IO_OR_GS_CODE();
-    bdrv_do_drained_end(bs, true, NULL, false);
-}
-
-void bdrv_apply_subtree_drain(BdrvChild *child, BlockDriverState *new_parent)
-{
-    int i;
-    IO_OR_GS_CODE();
-
-    for (i = 0; i < new_parent->recursive_quiesce_counter; i++) {
-        bdrv_do_drained_begin(child->bs, true, child, false, true);
-    }
-}
-
-void bdrv_unapply_subtree_drain(BdrvChild *child, BlockDriverState *old_parent)
-{
-    int i;
-    IO_OR_GS_CODE();
-
-    for (i = 0; i < old_parent->recursive_quiesce_counter; i++) {
-        bdrv_do_drained_end(child->bs, true, child, false);
-    }
+    bdrv_do_drained_end(bs, NULL, false);
 }
 
 void bdrv_drain(BlockDriverState *bs)
@@ -529,7 +460,7 @@ static bool bdrv_drain_all_poll(void)
     while ((bs = bdrv_next_all_states(bs))) {
         AioContext *aio_context = bdrv_get_aio_context(bs);
         aio_context_acquire(aio_context);
-        result |= bdrv_drain_poll(bs, false, NULL, true);
+        result |= bdrv_drain_poll(bs, NULL, true);
         aio_context_release(aio_context);
     }
 
@@ -554,7 +485,7 @@ void bdrv_drain_all_begin(void)
     GLOBAL_STATE_CODE();
 
     if (qemu_in_coroutine()) {
-        bdrv_co_yield_to_drain(NULL, true, false, NULL, true, true);
+        bdrv_co_yield_to_drain(NULL, true, NULL, true, true);
         return;
     }
 
@@ -579,7 +510,7 @@ void bdrv_drain_all_begin(void)
         AioContext *aio_context = bdrv_get_aio_context(bs);
 
         aio_context_acquire(aio_context);
-        bdrv_do_drained_begin(bs, false, NULL, true, false);
+        bdrv_do_drained_begin(bs, NULL, true, false);
         aio_context_release(aio_context);
     }
 
@@ -599,7 +530,7 @@ void bdrv_drain_all_end_quiesce(BlockDriverState *bs)
     g_assert(!bs->refcnt);
 
     while (bs->quiesce_counter) {
-        bdrv_do_drained_end(bs, false, NULL, true);
+        bdrv_do_drained_end(bs, NULL, true);
     }
 }
 
@@ -621,7 +552,7 @@ void bdrv_drain_all_end(void)
         AioContext *aio_context = bdrv_get_aio_context(bs);
 
         aio_context_acquire(aio_context);
-        bdrv_do_drained_end(bs, false, NULL, true);
+        bdrv_do_drained_end(bs, NULL, true);
         aio_context_release(aio_context);
     }
 
diff --git a/include/block/block-io.h b/include/block/block-io.h
index 054e964c9b..9c36a16a1f 100644
--- a/include/block/block-io.h
+++ b/include/block/block-io.h
@@ -302,8 +302,7 @@ void bdrv_parent_drained_end_single(BdrvChild *c);
 /**
  * bdrv_drain_poll:
  *
- * Poll for pending requests in @bs, its parents (except for @ignore_parent),
- * and if @recursive is true its children as well (used for subtree drain).
+ * Poll for pending requests in @bs and its parents (except for @ignore_parent).
  *
  * If @ignore_bds_parents is true, parents that are BlockDriverStates must
  * ignore the drain request because they will be drained separately (used for
@@ -311,8 +310,8 @@ void bdrv_parent_drained_end_single(BdrvChild *c);
  *
  * This is part of bdrv_drained_begin.
  */
-bool bdrv_drain_poll(BlockDriverState *bs, bool recursive,
-                     BdrvChild *ignore_parent, bool ignore_bds_parents);
+bool bdrv_drain_poll(BlockDriverState *bs, BdrvChild *ignore_parent,
+                     bool ignore_bds_parents);
 
 /**
  * bdrv_drained_begin:
@@ -333,12 +332,6 @@ void bdrv_drained_begin(BlockDriverState *bs);
 void bdrv_do_drained_begin_quiesce(BlockDriverState *bs,
                                    BdrvChild *parent, bool ignore_bds_parents);
 
-/**
- * Like bdrv_drained_begin, but recursively begins a quiesced section for
- * exclusive access to all child nodes as well.
- */
-void bdrv_subtree_drained_begin(BlockDriverState *bs);
-
 /**
  * bdrv_drained_end:
  *
@@ -346,9 +339,4 @@ void bdrv_subtree_drained_begin(BlockDriverState *bs);
  */
 void bdrv_drained_end(BlockDriverState *bs);
 
-/**
- * End a quiescent section started by bdrv_subtree_drained_begin().
- */
-void bdrv_subtree_drained_end(BlockDriverState *bs);
-
 #endif /* BLOCK_IO_H */
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 2b97576f6d..791dddfd7d 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -1184,7 +1184,6 @@ struct BlockDriverState {
 
     /* Accessed with atomic ops.  */
     int quiesce_counter;
-    int recursive_quiesce_counter;
 
     unsigned int write_gen;               /* Current data generation */
 
diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h
index 4b0b3e17ef..8bc061ebb8 100644
--- a/include/block/block_int-io.h
+++ b/include/block/block_int-io.h
@@ -179,16 +179,4 @@ void bdrv_bsc_invalidate_range(BlockDriverState *bs,
  */
 void bdrv_bsc_fill(BlockDriverState *bs, int64_t offset, int64_t bytes);
 
-
-/*
- * "I/O or GS" API functions. These functions can run without
- * the BQL, but only in one specific iothread/main loop.
- *
- * See include/block/block-io.h for more information about
- * the "I/O or GS" API.
- */
-
-void bdrv_apply_subtree_drain(BdrvChild *child, BlockDriverState *new_parent);
-void bdrv_unapply_subtree_drain(BdrvChild *child, BlockDriverState *old_parent);
-
 #endif /* BLOCK_INT_IO_H */
diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c
index 695519ee02..dda08de8db 100644
--- a/tests/unit/test-bdrv-drain.c
+++ b/tests/unit/test-bdrv-drain.c
@@ -156,7 +156,6 @@ static void call_in_coroutine(void (*entry)(void))
 enum drain_type {
     BDRV_DRAIN_ALL,
     BDRV_DRAIN,
-    BDRV_SUBTREE_DRAIN,
     DRAIN_TYPE_MAX,
 };
 
@@ -165,7 +164,6 @@ static void do_drain_begin(enum drain_type drain_type, BlockDriverState *bs)
     switch (drain_type) {
     case BDRV_DRAIN_ALL:        bdrv_drain_all_begin(); break;
     case BDRV_DRAIN:            bdrv_drained_begin(bs); break;
-    case BDRV_SUBTREE_DRAIN:    bdrv_subtree_drained_begin(bs); break;
     default:                    g_assert_not_reached();
     }
 }
@@ -175,7 +173,6 @@ static void do_drain_end(enum drain_type drain_type, BlockDriverState *bs)
     switch (drain_type) {
     case BDRV_DRAIN_ALL:        bdrv_drain_all_end(); break;
     case BDRV_DRAIN:            bdrv_drained_end(bs); break;
-    case BDRV_SUBTREE_DRAIN:    bdrv_subtree_drained_end(bs); break;
     default:                    g_assert_not_reached();
     }
 }
@@ -271,11 +268,6 @@ static void test_drv_cb_drain(void)
     test_drv_cb_common(BDRV_DRAIN, false);
 }
 
-static void test_drv_cb_drain_subtree(void)
-{
-    test_drv_cb_common(BDRV_SUBTREE_DRAIN, true);
-}
-
 static void test_drv_cb_co_drain_all(void)
 {
     call_in_coroutine(test_drv_cb_drain_all);
@@ -286,11 +278,6 @@ static void test_drv_cb_co_drain(void)
     call_in_coroutine(test_drv_cb_drain);
 }
 
-static void test_drv_cb_co_drain_subtree(void)
-{
-    call_in_coroutine(test_drv_cb_drain_subtree);
-}
-
 static void test_quiesce_common(enum drain_type drain_type, bool recursive)
 {
     BlockBackend *blk;
@@ -332,11 +319,6 @@ static void test_quiesce_drain(void)
     test_quiesce_common(BDRV_DRAIN, false);
 }
 
-static void test_quiesce_drain_subtree(void)
-{
-    test_quiesce_common(BDRV_SUBTREE_DRAIN, true);
-}
-
 static void test_quiesce_co_drain_all(void)
 {
     call_in_coroutine(test_quiesce_drain_all);
@@ -347,11 +329,6 @@ static void test_quiesce_co_drain(void)
     call_in_coroutine(test_quiesce_drain);
 }
 
-static void test_quiesce_co_drain_subtree(void)
-{
-    call_in_coroutine(test_quiesce_drain_subtree);
-}
-
 static void test_nested(void)
 {
     BlockBackend *blk;
@@ -402,158 +379,6 @@ static void test_nested(void)
     blk_unref(blk);
 }
 
-static void test_multiparent(void)
-{
-    BlockBackend *blk_a, *blk_b;
-    BlockDriverState *bs_a, *bs_b, *backing;
-    BDRVTestState *a_s, *b_s, *backing_s;
-
-    blk_a = blk_new(qemu_get_aio_context(), BLK_PERM_ALL, BLK_PERM_ALL);
-    bs_a = bdrv_new_open_driver(&bdrv_test, "test-node-a", BDRV_O_RDWR,
-                                &error_abort);
-    a_s = bs_a->opaque;
-    blk_insert_bs(blk_a, bs_a, &error_abort);
-
-    blk_b = blk_new(qemu_get_aio_context(), BLK_PERM_ALL, BLK_PERM_ALL);
-    bs_b = bdrv_new_open_driver(&bdrv_test, "test-node-b", BDRV_O_RDWR,
-                                &error_abort);
-    b_s = bs_b->opaque;
-    blk_insert_bs(blk_b, bs_b, &error_abort);
-
-    backing = bdrv_new_open_driver(&bdrv_test, "backing", 0, &error_abort);
-    backing_s = backing->opaque;
-    bdrv_set_backing_hd(bs_a, backing, &error_abort);
-    bdrv_set_backing_hd(bs_b, backing, &error_abort);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 0);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 0);
-    g_assert_cmpint(backing->quiesce_counter, ==, 0);
-    g_assert_cmpint(a_s->drain_count, ==, 0);
-    g_assert_cmpint(b_s->drain_count, ==, 0);
-    g_assert_cmpint(backing_s->drain_count, ==, 0);
-
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_a);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 1);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 1);
-    g_assert_cmpint(backing->quiesce_counter, ==, 1);
-    g_assert_cmpint(a_s->drain_count, ==, 1);
-    g_assert_cmpint(b_s->drain_count, ==, 1);
-    g_assert_cmpint(backing_s->drain_count, ==, 1);
-
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_b);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 2);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 2);
-    g_assert_cmpint(backing->quiesce_counter, ==, 2);
-    g_assert_cmpint(a_s->drain_count, ==, 2);
-    g_assert_cmpint(b_s->drain_count, ==, 2);
-    g_assert_cmpint(backing_s->drain_count, ==, 2);
-
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_b);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 1);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 1);
-    g_assert_cmpint(backing->quiesce_counter, ==, 1);
-    g_assert_cmpint(a_s->drain_count, ==, 1);
-    g_assert_cmpint(b_s->drain_count, ==, 1);
-    g_assert_cmpint(backing_s->drain_count, ==, 1);
-
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_a);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 0);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 0);
-    g_assert_cmpint(backing->quiesce_counter, ==, 0);
-    g_assert_cmpint(a_s->drain_count, ==, 0);
-    g_assert_cmpint(b_s->drain_count, ==, 0);
-    g_assert_cmpint(backing_s->drain_count, ==, 0);
-
-    bdrv_unref(backing);
-    bdrv_unref(bs_a);
-    bdrv_unref(bs_b);
-    blk_unref(blk_a);
-    blk_unref(blk_b);
-}
-
-static void test_graph_change_drain_subtree(void)
-{
-    BlockBackend *blk_a, *blk_b;
-    BlockDriverState *bs_a, *bs_b, *backing;
-    BDRVTestState *a_s, *b_s, *backing_s;
-
-    blk_a = blk_new(qemu_get_aio_context(), BLK_PERM_ALL, BLK_PERM_ALL);
-    bs_a = bdrv_new_open_driver(&bdrv_test, "test-node-a", BDRV_O_RDWR,
-                                &error_abort);
-    a_s = bs_a->opaque;
-    blk_insert_bs(blk_a, bs_a, &error_abort);
-
-    blk_b = blk_new(qemu_get_aio_context(), BLK_PERM_ALL, BLK_PERM_ALL);
-    bs_b = bdrv_new_open_driver(&bdrv_test, "test-node-b", BDRV_O_RDWR,
-                                &error_abort);
-    b_s = bs_b->opaque;
-    blk_insert_bs(blk_b, bs_b, &error_abort);
-
-    backing = bdrv_new_open_driver(&bdrv_test, "backing", 0, &error_abort);
-    backing_s = backing->opaque;
-    bdrv_set_backing_hd(bs_a, backing, &error_abort);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 0);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 0);
-    g_assert_cmpint(backing->quiesce_counter, ==, 0);
-    g_assert_cmpint(a_s->drain_count, ==, 0);
-    g_assert_cmpint(b_s->drain_count, ==, 0);
-    g_assert_cmpint(backing_s->drain_count, ==, 0);
-
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_a);
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_a);
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_a);
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_b);
-    do_drain_begin(BDRV_SUBTREE_DRAIN, bs_b);
-
-    bdrv_set_backing_hd(bs_b, backing, &error_abort);
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 5);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 5);
-    g_assert_cmpint(backing->quiesce_counter, ==, 5);
-    g_assert_cmpint(a_s->drain_count, ==, 5);
-    g_assert_cmpint(b_s->drain_count, ==, 5);
-    g_assert_cmpint(backing_s->drain_count, ==, 5);
-
-    bdrv_set_backing_hd(bs_b, NULL, &error_abort);
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 3);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 2);
-    g_assert_cmpint(backing->quiesce_counter, ==, 3);
-    g_assert_cmpint(a_s->drain_count, ==, 3);
-    g_assert_cmpint(b_s->drain_count, ==, 2);
-    g_assert_cmpint(backing_s->drain_count, ==, 3);
-
-    bdrv_set_backing_hd(bs_b, backing, &error_abort);
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 5);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 5);
-    g_assert_cmpint(backing->quiesce_counter, ==, 5);
-    g_assert_cmpint(a_s->drain_count, ==, 5);
-    g_assert_cmpint(b_s->drain_count, ==, 5);
-    g_assert_cmpint(backing_s->drain_count, ==, 5);
-
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_b);
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_b);
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_a);
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_a);
-    do_drain_end(BDRV_SUBTREE_DRAIN, bs_a);
-
-    g_assert_cmpint(bs_a->quiesce_counter, ==, 0);
-    g_assert_cmpint(bs_b->quiesce_counter, ==, 0);
-    g_assert_cmpint(backing->quiesce_counter, ==, 0);
-    g_assert_cmpint(a_s->drain_count, ==, 0);
-    g_assert_cmpint(b_s->drain_count, ==, 0);
-    g_assert_cmpint(backing_s->drain_count, ==, 0);
-
-    bdrv_unref(backing);
-    bdrv_unref(bs_a);
-    bdrv_unref(bs_b);
-    blk_unref(blk_a);
-    blk_unref(blk_b);
-}
-
 static void test_graph_change_drain_all(void)
 {
     BlockBackend *blk_a, *blk_b;
@@ -773,12 +598,6 @@ static void test_iothread_drain(void)
     test_iothread_common(BDRV_DRAIN, 1);
 }
 
-static void test_iothread_drain_subtree(void)
-{
-    test_iothread_common(BDRV_SUBTREE_DRAIN, 0);
-    test_iothread_common(BDRV_SUBTREE_DRAIN, 1);
-}
-
 
 typedef struct TestBlockJob {
     BlockJob common;
@@ -863,7 +682,6 @@ enum test_job_result {
 enum test_job_drain_node {
     TEST_JOB_DRAIN_SRC,
     TEST_JOB_DRAIN_SRC_CHILD,
-    TEST_JOB_DRAIN_SRC_PARENT,
 };
 
 static void test_blockjob_common_drain_node(enum drain_type drain_type,
@@ -901,9 +719,6 @@ static void test_blockjob_common_drain_node(enum drain_type drain_type,
     case TEST_JOB_DRAIN_SRC_CHILD:
         drain_bs = src_backing;
         break;
-    case TEST_JOB_DRAIN_SRC_PARENT:
-        drain_bs = src_overlay;
-        break;
     default:
         g_assert_not_reached();
     }
@@ -1055,10 +870,6 @@ static void test_blockjob_common(enum drain_type drain_type, bool use_iothread,
                                     TEST_JOB_DRAIN_SRC);
     test_blockjob_common_drain_node(drain_type, use_iothread, result,
                                     TEST_JOB_DRAIN_SRC_CHILD);
-    if (drain_type == BDRV_SUBTREE_DRAIN) {
-        test_blockjob_common_drain_node(drain_type, use_iothread, result,
-                                        TEST_JOB_DRAIN_SRC_PARENT);
-    }
 }
 
 static void test_blockjob_drain_all(void)
@@ -1071,11 +882,6 @@ static void test_blockjob_drain(void)
     test_blockjob_common(BDRV_DRAIN, false, TEST_JOB_SUCCESS);
 }
 
-static void test_blockjob_drain_subtree(void)
-{
-    test_blockjob_common(BDRV_SUBTREE_DRAIN, false, TEST_JOB_SUCCESS);
-}
-
 static void test_blockjob_error_drain_all(void)
 {
     test_blockjob_common(BDRV_DRAIN_ALL, false, TEST_JOB_FAIL_RUN);
@@ -1088,12 +894,6 @@ static void test_blockjob_error_drain(void)
     test_blockjob_common(BDRV_DRAIN, false, TEST_JOB_FAIL_PREPARE);
 }
 
-static void test_blockjob_error_drain_subtree(void)
-{
-    test_blockjob_common(BDRV_SUBTREE_DRAIN, false, TEST_JOB_FAIL_RUN);
-    test_blockjob_common(BDRV_SUBTREE_DRAIN, false, TEST_JOB_FAIL_PREPARE);
-}
-
 static void test_blockjob_iothread_drain_all(void)
 {
     test_blockjob_common(BDRV_DRAIN_ALL, true, TEST_JOB_SUCCESS);
@@ -1104,11 +904,6 @@ static void test_blockjob_iothread_drain(void)
     test_blockjob_common(BDRV_DRAIN, true, TEST_JOB_SUCCESS);
 }
 
-static void test_blockjob_iothread_drain_subtree(void)
-{
-    test_blockjob_common(BDRV_SUBTREE_DRAIN, true, TEST_JOB_SUCCESS);
-}
-
 static void test_blockjob_iothread_error_drain_all(void)
 {
     test_blockjob_common(BDRV_DRAIN_ALL, true, TEST_JOB_FAIL_RUN);
@@ -1121,12 +916,6 @@ static void test_blockjob_iothread_error_drain(void)
     test_blockjob_common(BDRV_DRAIN, true, TEST_JOB_FAIL_PREPARE);
 }
 
-static void test_blockjob_iothread_error_drain_subtree(void)
-{
-    test_blockjob_common(BDRV_SUBTREE_DRAIN, true, TEST_JOB_FAIL_RUN);
-    test_blockjob_common(BDRV_SUBTREE_DRAIN, true, TEST_JOB_FAIL_PREPARE);
-}
-
 
 typedef struct BDRVTestTopState {
     BdrvChild *wait_child;
@@ -1273,14 +1062,6 @@ static void do_test_delete_by_drain(bool detach_instead_of_delete,
         bdrv_drain(child_bs);
         bdrv_unref(child_bs);
         break;
-    case BDRV_SUBTREE_DRAIN:
-        /* Would have to ref/unref bs here for !detach_instead_of_delete, but
-         * then the whole test becomes pointless because the graph changes
-         * don't occur during the drain any more. */
-        assert(detach_instead_of_delete);
-        bdrv_subtree_drained_begin(bs);
-        bdrv_subtree_drained_end(bs);
-        break;
     case BDRV_DRAIN_ALL:
         bdrv_drain_all_begin();
         bdrv_drain_all_end();
@@ -1315,11 +1096,6 @@ static void test_detach_by_drain(void)
     do_test_delete_by_drain(true, BDRV_DRAIN);
 }
 
-static void test_detach_by_drain_subtree(void)
-{
-    do_test_delete_by_drain(true, BDRV_SUBTREE_DRAIN);
-}
-
 
 struct detach_by_parent_data {
     BlockDriverState *parent_b;
@@ -1452,7 +1228,10 @@ static void test_detach_indirect(bool by_parent_cb)
     g_assert(acb != NULL);
 
     /* Drain and check the expected result */
-    bdrv_subtree_drained_begin(parent_b);
+    bdrv_drained_begin(parent_b);
+    bdrv_drained_begin(a);
+    bdrv_drained_begin(b);
+    bdrv_drained_begin(c);
 
     g_assert(detach_by_parent_data.child_c != NULL);
 
@@ -1467,12 +1246,15 @@ static void test_detach_indirect(bool by_parent_cb)
     g_assert(QLIST_NEXT(child_a, next) == NULL);
 
     g_assert_cmpint(parent_a->quiesce_counter, ==, 1);
-    g_assert_cmpint(parent_b->quiesce_counter, ==, 1);
+    g_assert_cmpint(parent_b->quiesce_counter, ==, 3);
     g_assert_cmpint(a->quiesce_counter, ==, 1);
-    g_assert_cmpint(b->quiesce_counter, ==, 0);
+    g_assert_cmpint(b->quiesce_counter, ==, 1);
     g_assert_cmpint(c->quiesce_counter, ==, 1);
 
-    bdrv_subtree_drained_end(parent_b);
+    bdrv_drained_end(parent_b);
+    bdrv_drained_end(a);
+    bdrv_drained_end(b);
+    bdrv_drained_end(c);
 
     bdrv_unref(parent_b);
     blk_unref(blk);
@@ -2202,70 +1984,47 @@ int main(int argc, char **argv)
 
     g_test_add_func("/bdrv-drain/driver-cb/drain_all", test_drv_cb_drain_all);
     g_test_add_func("/bdrv-drain/driver-cb/drain", test_drv_cb_drain);
-    g_test_add_func("/bdrv-drain/driver-cb/drain_subtree",
-                    test_drv_cb_drain_subtree);
 
     g_test_add_func("/bdrv-drain/driver-cb/co/drain_all",
                     test_drv_cb_co_drain_all);
     g_test_add_func("/bdrv-drain/driver-cb/co/drain", test_drv_cb_co_drain);
-    g_test_add_func("/bdrv-drain/driver-cb/co/drain_subtree",
-                    test_drv_cb_co_drain_subtree);
-
 
     g_test_add_func("/bdrv-drain/quiesce/drain_all", test_quiesce_drain_all);
     g_test_add_func("/bdrv-drain/quiesce/drain", test_quiesce_drain);
-    g_test_add_func("/bdrv-drain/quiesce/drain_subtree",
-                    test_quiesce_drain_subtree);
 
     g_test_add_func("/bdrv-drain/quiesce/co/drain_all",
                     test_quiesce_co_drain_all);
     g_test_add_func("/bdrv-drain/quiesce/co/drain", test_quiesce_co_drain);
-    g_test_add_func("/bdrv-drain/quiesce/co/drain_subtree",
-                    test_quiesce_co_drain_subtree);
 
     g_test_add_func("/bdrv-drain/nested", test_nested);
-    g_test_add_func("/bdrv-drain/multiparent", test_multiparent);
 
-    g_test_add_func("/bdrv-drain/graph-change/drain_subtree",
-                    test_graph_change_drain_subtree);
     g_test_add_func("/bdrv-drain/graph-change/drain_all",
                     test_graph_change_drain_all);
 
     g_test_add_func("/bdrv-drain/iothread/drain_all", test_iothread_drain_all);
     g_test_add_func("/bdrv-drain/iothread/drain", test_iothread_drain);
-    g_test_add_func("/bdrv-drain/iothread/drain_subtree",
-                    test_iothread_drain_subtree);
 
     g_test_add_func("/bdrv-drain/blockjob/drain_all", test_blockjob_drain_all);
     g_test_add_func("/bdrv-drain/blockjob/drain", test_blockjob_drain);
-    g_test_add_func("/bdrv-drain/blockjob/drain_subtree",
-                    test_blockjob_drain_subtree);
 
     g_test_add_func("/bdrv-drain/blockjob/error/drain_all",
                     test_blockjob_error_drain_all);
     g_test_add_func("/bdrv-drain/blockjob/error/drain",
                     test_blockjob_error_drain);
-    g_test_add_func("/bdrv-drain/blockjob/error/drain_subtree",
-                    test_blockjob_error_drain_subtree);
 
     g_test_add_func("/bdrv-drain/blockjob/iothread/drain_all",
                     test_blockjob_iothread_drain_all);
     g_test_add_func("/bdrv-drain/blockjob/iothread/drain",
                     test_blockjob_iothread_drain);
-    g_test_add_func("/bdrv-drain/blockjob/iothread/drain_subtree",
-                    test_blockjob_iothread_drain_subtree);
 
     g_test_add_func("/bdrv-drain/blockjob/iothread/error/drain_all",
                     test_blockjob_iothread_error_drain_all);
     g_test_add_func("/bdrv-drain/blockjob/iothread/error/drain",
                     test_blockjob_iothread_error_drain);
-    g_test_add_func("/bdrv-drain/blockjob/iothread/error/drain_subtree",
-                    test_blockjob_iothread_error_drain_subtree);
 
     g_test_add_func("/bdrv-drain/deletion/drain", test_delete_by_drain);
     g_test_add_func("/bdrv-drain/detach/drain_all", test_detach_by_drain_all);
     g_test_add_func("/bdrv-drain/detach/drain", test_detach_by_drain);
-    g_test_add_func("/bdrv-drain/detach/drain_subtree", test_detach_by_drain_subtree);
     g_test_add_func("/bdrv-drain/detach/parent_cb", test_detach_by_parent_cb);
     g_test_add_func("/bdrv-drain/detach/driver_cb", test_detach_by_driver_cb);
 
-- 
2.31.1