[mirror_qemu.git] / tests / test-bdrv-drain.c

/*
 * Block node draining tests
 *
 * Copyright (c) 2017 Kevin Wolf <kwolf@redhat.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "block/block.h"
#include "block/blockjob_int.h"
#include "sysemu/block-backend.h"
#include "qapi/error.h"
#include "iothread.h"

static QemuEvent done_event;

typedef struct BDRVTestState {
    int drain_count;
    AioContext *bh_indirection_ctx;
    bool sleep_in_drain_begin;
} BDRVTestState;

static void coroutine_fn bdrv_test_co_drain_begin(BlockDriverState *bs)
{
    BDRVTestState *s = bs->opaque;
    s->drain_count++;
    if (s->sleep_in_drain_begin) {
        qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 100000);
    }
}

static void coroutine_fn bdrv_test_co_drain_end(BlockDriverState *bs)
{
    BDRVTestState *s = bs->opaque;
    s->drain_count--;
}

static void bdrv_test_close(BlockDriverState *bs)
{
    BDRVTestState *s = bs->opaque;
    g_assert_cmpint(s->drain_count, >, 0);
}

static void co_reenter_bh(void *opaque)
{
    aio_co_wake(opaque);
}

static int coroutine_fn bdrv_test_co_preadv(BlockDriverState *bs,
                                            uint64_t offset, uint64_t bytes,
                                            QEMUIOVector *qiov, int flags)
{
    BDRVTestState *s = bs->opaque;

    /* We want this request to stay until the polling loop in drain waits for
     * it to complete. We need to sleep a while as bdrv_drain_invoke() comes
     * first and polls its result, too, but it shouldn't accidentally complete
     * this request yet. */
    qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 100000);

    if (s->bh_indirection_ctx) {
        aio_bh_schedule_oneshot(s->bh_indirection_ctx, co_reenter_bh,
                                qemu_coroutine_self());
        qemu_coroutine_yield();
    }

    return 0;
}

static void bdrv_test_child_perm(BlockDriverState *bs, BdrvChild *c,
                                 const BdrvChildRole *role,
                                 BlockReopenQueue *reopen_queue,
                                 uint64_t perm, uint64_t shared,
                                 uint64_t *nperm, uint64_t *nshared)
{
    /* bdrv_format_default_perms() accepts only these two, so disguise
     * detach_by_driver_cb_role as one of them. */
    if (role != &child_file && role != &child_backing) {
        role = &child_file;
    }

    bdrv_format_default_perms(bs, c, role, reopen_queue, perm, shared,
                              nperm, nshared);
}

static BlockDriver bdrv_test = {
    .format_name            = "test",
    .instance_size          = sizeof(BDRVTestState),

    .bdrv_close             = bdrv_test_close,
    .bdrv_co_preadv         = bdrv_test_co_preadv,

    .bdrv_co_drain_begin    = bdrv_test_co_drain_begin,
    .bdrv_co_drain_end      = bdrv_test_co_drain_end,

    .bdrv_child_perm        = bdrv_test_child_perm,
};

static void aio_ret_cb(void *opaque, int ret)
{
    int *aio_ret = opaque;
    *aio_ret = ret;
}

typedef struct CallInCoroutineData {
    void (*entry)(void);
    bool done;
} CallInCoroutineData;

static coroutine_fn void call_in_coroutine_entry(void *opaque)
{
    CallInCoroutineData *data = opaque;

    data->entry();
    data->done = true;
}

static void call_in_coroutine(void (*entry)(void))
{
    Coroutine *co;
    CallInCoroutineData data = {
        .entry  = entry,
        .done   = false,
    };

    co = qemu_coroutine_create(call_in_coroutine_entry, &data);
    qemu_coroutine_enter(co);
    while (!data.done) {
        aio_poll(qemu_get_aio_context(), true);
    }
}

enum drain_type {
    BDRV_DRAIN_ALL,
    BDRV_DRAIN,
    BDRV_SUBTREE_DRAIN,
    DRAIN_TYPE_MAX,
};

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();
    }
}

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();
    }
}

static void do_drain_begin_unlocked(enum drain_type drain_type, BlockDriverState *bs)
{
    if (drain_type != BDRV_DRAIN_ALL) {
        aio_context_acquire(bdrv_get_aio_context(bs));
    }
    do_drain_begin(drain_type, bs);
    if (drain_type != BDRV_DRAIN_ALL) {
        aio_context_release(bdrv_get_aio_context(bs));
    }
}

static void do_drain_end_unlocked(enum drain_type drain_type, BlockDriverState *bs)
{
    if (drain_type != BDRV_DRAIN_ALL) {
        aio_context_acquire(bdrv_get_aio_context(bs));
    }
    do_drain_end(drain_type, bs);
    if (drain_type != BDRV_DRAIN_ALL) {
        aio_context_release(bdrv_get_aio_context(bs));
    }
}

static void test_drv_cb_common(enum drain_type drain_type, bool recursive)
{
    BlockBackend *blk;
    BlockDriverState *bs, *backing;
    BDRVTestState *s, *backing_s;
    BlockAIOCB *acb;
    int aio_ret;

    QEMUIOVector qiov;
    struct iovec iov = {
        .iov_base = NULL,
        .iov_len = 0,
    };
    qemu_iovec_init_external(&qiov, &iov, 1);

    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    bs = bdrv_new_open_driver(&bdrv_test, "test-node", BDRV_O_RDWR,
                              &error_abort);
    s = bs->opaque;
    blk_insert_bs(blk, bs, &error_abort);

    backing = bdrv_new_open_driver(&bdrv_test, "backing", 0, &error_abort);
    backing_s = backing->opaque;
    bdrv_set_backing_hd(bs, backing, &error_abort);

    /* Simple bdrv_drain_all_begin/end pair, check that CBs are called */
    g_assert_cmpint(s->drain_count, ==, 0);
    g_assert_cmpint(backing_s->drain_count, ==, 0);

    do_drain_begin(drain_type, bs);

    g_assert_cmpint(s->drain_count, ==, 1);
    g_assert_cmpint(backing_s->drain_count, ==, !!recursive);

    do_drain_end(drain_type, bs);

    g_assert_cmpint(s->drain_count, ==, 0);
    g_assert_cmpint(backing_s->drain_count, ==, 0);

    /* Now do the same while a request is pending */
    aio_ret = -EINPROGRESS;
    acb = blk_aio_preadv(blk, 0, &qiov, 0, aio_ret_cb, &aio_ret);
    g_assert(acb != NULL);
    g_assert_cmpint(aio_ret, ==, -EINPROGRESS);

    g_assert_cmpint(s->drain_count, ==, 0);
    g_assert_cmpint(backing_s->drain_count, ==, 0);

    do_drain_begin(drain_type, bs);

    g_assert_cmpint(aio_ret, ==, 0);
    g_assert_cmpint(s->drain_count, ==, 1);
    g_assert_cmpint(backing_s->drain_count, ==, !!recursive);

    do_drain_end(drain_type, bs);

    g_assert_cmpint(s->drain_count, ==, 0);
    g_assert_cmpint(backing_s->drain_count, ==, 0);

    bdrv_unref(backing);
    bdrv_unref(bs);
    blk_unref(blk);
}

static void test_drv_cb_drain_all(void)
{
    test_drv_cb_common(BDRV_DRAIN_ALL, true);
}

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);
}

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;
    BlockDriverState *bs, *backing;

    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    bs = bdrv_new_open_driver(&bdrv_test, "test-node", BDRV_O_RDWR,
                              &error_abort);
    blk_insert_bs(blk, bs, &error_abort);

    backing = bdrv_new_open_driver(&bdrv_test, "backing", 0, &error_abort);
    bdrv_set_backing_hd(bs, backing, &error_abort);

    g_assert_cmpint(bs->quiesce_counter, ==, 0);
    g_assert_cmpint(backing->quiesce_counter, ==, 0);

    do_drain_begin(drain_type, bs);

    g_assert_cmpint(bs->quiesce_counter, ==, 1);
    g_assert_cmpint(backing->quiesce_counter, ==, !!recursive);

    do_drain_end(drain_type, bs);

    g_assert_cmpint(bs->quiesce_counter, ==, 0);
    g_assert_cmpint(backing->quiesce_counter, ==, 0);

    bdrv_unref(backing);
    bdrv_unref(bs);
    blk_unref(blk);
}

static void test_quiesce_drain_all(void)
{
    test_quiesce_common(BDRV_DRAIN_ALL, true);
}

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);
}

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;
    BlockDriverState *bs, *backing;
    BDRVTestState *s, *backing_s;
    enum drain_type outer, inner;

    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    bs = bdrv_new_open_driver(&bdrv_test, "test-node", BDRV_O_RDWR,
                              &error_abort);
    s = bs->opaque;
    blk_insert_bs(blk, bs, &error_abort);

    backing = bdrv_new_open_driver(&bdrv_test, "backing", 0, &error_abort);
    backing_s = backing->opaque;
    bdrv_set_backing_hd(bs, backing, &error_abort);

    for (outer = 0; outer < DRAIN_TYPE_MAX; outer++) {
        for (inner = 0; inner < DRAIN_TYPE_MAX; inner++) {
            int backing_quiesce = (outer != BDRV_DRAIN) +
                                  (inner != BDRV_DRAIN);

            g_assert_cmpint(bs->quiesce_counter, ==, 0);
            g_assert_cmpint(backing->quiesce_counter, ==, 0);
            g_assert_cmpint(s->drain_count, ==, 0);
            g_assert_cmpint(backing_s->drain_count, ==, 0);

            do_drain_begin(outer, bs);
            do_drain_begin(inner, bs);

            g_assert_cmpint(bs->quiesce_counter, ==, 2);
            g_assert_cmpint(backing->quiesce_counter, ==, backing_quiesce);
            g_assert_cmpint(s->drain_count, ==, 2);
            g_assert_cmpint(backing_s->drain_count, ==, backing_quiesce);

            do_drain_end(inner, bs);
            do_drain_end(outer, bs);

            g_assert_cmpint(bs->quiesce_counter, ==, 0);
            g_assert_cmpint(backing->quiesce_counter, ==, 0);
            g_assert_cmpint(s->drain_count, ==, 0);
            g_assert_cmpint(backing_s->drain_count, ==, 0);
        }
    }

    bdrv_unref(backing);
    bdrv_unref(bs);
    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(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(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(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(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;
    BlockDriverState *bs_a, *bs_b;
    BDRVTestState *a_s, *b_s;

    /* Create node A with a BlockBackend */
    blk_a = blk_new(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);

    g_assert_cmpint(bs_a->quiesce_counter, ==, 0);
    g_assert_cmpint(a_s->drain_count, ==, 0);

    /* Call bdrv_drain_all_begin() */
    bdrv_drain_all_begin();

    g_assert_cmpint(bs_a->quiesce_counter, ==, 1);
    g_assert_cmpint(a_s->drain_count, ==, 1);

    /* Create node B with a BlockBackend */
    blk_b = blk_new(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);

    g_assert_cmpint(bs_a->quiesce_counter, ==, 1);
    g_assert_cmpint(bs_b->quiesce_counter, ==, 1);
    g_assert_cmpint(a_s->drain_count, ==, 1);
    g_assert_cmpint(b_s->drain_count, ==, 1);

    /* Unref and finally delete node A */
    blk_unref(blk_a);

    g_assert_cmpint(bs_a->quiesce_counter, ==, 1);
    g_assert_cmpint(bs_b->quiesce_counter, ==, 1);
    g_assert_cmpint(a_s->drain_count, ==, 1);
    g_assert_cmpint(b_s->drain_count, ==, 1);

    bdrv_unref(bs_a);

    g_assert_cmpint(bs_b->quiesce_counter, ==, 1);
    g_assert_cmpint(b_s->drain_count, ==, 1);

    /* End the drained section */
    bdrv_drain_all_end();

    g_assert_cmpint(bs_b->quiesce_counter, ==, 0);
    g_assert_cmpint(b_s->drain_count, ==, 0);

    bdrv_unref(bs_b);
    blk_unref(blk_b);
}

struct test_iothread_data {
    BlockDriverState *bs;
    enum drain_type drain_type;
    int *aio_ret;
};

static void test_iothread_drain_entry(void *opaque)
{
    struct test_iothread_data *data = opaque;

    aio_context_acquire(bdrv_get_aio_context(data->bs));
    do_drain_begin(data->drain_type, data->bs);
    g_assert_cmpint(*data->aio_ret, ==, 0);
    do_drain_end(data->drain_type, data->bs);
    aio_context_release(bdrv_get_aio_context(data->bs));

    qemu_event_set(&done_event);
}

static void test_iothread_aio_cb(void *opaque, int ret)
{
    int *aio_ret = opaque;
    *aio_ret = ret;
    qemu_event_set(&done_event);
}

static void test_iothread_main_thread_bh(void *opaque)
{
    struct test_iothread_data *data = opaque;

    /* Test that the AioContext is not yet locked in a random BH that is
     * executed during drain, otherwise this would deadlock. */
    aio_context_acquire(bdrv_get_aio_context(data->bs));
    bdrv_flush(data->bs);
    aio_context_release(bdrv_get_aio_context(data->bs));
}

/*
 * Starts an AIO request on a BDS that runs in the AioContext of iothread 1.
 * The request involves a BH on iothread 2 before it can complete.
 *
 * @drain_thread = 0 means that do_drain_begin/end are called from the main
 * thread, @drain_thread = 1 means that they are called from iothread 1. Drain
 * for this BDS cannot be called from iothread 2 because only the main thread
 * may do cross-AioContext polling.
 */
static void test_iothread_common(enum drain_type drain_type, int drain_thread)
{
    BlockBackend *blk;
    BlockDriverState *bs;
    BDRVTestState *s;
    BlockAIOCB *acb;
    int aio_ret;
    struct test_iothread_data data;

    IOThread *a = iothread_new();
    IOThread *b = iothread_new();
    AioContext *ctx_a = iothread_get_aio_context(a);
    AioContext *ctx_b = iothread_get_aio_context(b);

    QEMUIOVector qiov;
    struct iovec iov = {
        .iov_base = NULL,
        .iov_len = 0,
    };
    qemu_iovec_init_external(&qiov, &iov, 1);

    /* bdrv_drain_all() may only be called from the main loop thread */
    if (drain_type == BDRV_DRAIN_ALL && drain_thread != 0) {
        goto out;
    }

    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    bs = bdrv_new_open_driver(&bdrv_test, "test-node", BDRV_O_RDWR,
                              &error_abort);
    s = bs->opaque;
    blk_insert_bs(blk, bs, &error_abort);

    blk_set_aio_context(blk, ctx_a);
    aio_context_acquire(ctx_a);

    s->bh_indirection_ctx = ctx_b;

    aio_ret = -EINPROGRESS;
    if (drain_thread == 0) {
        acb = blk_aio_preadv(blk, 0, &qiov, 0, test_iothread_aio_cb, &aio_ret);
    } else {
        acb = blk_aio_preadv(blk, 0, &qiov, 0, aio_ret_cb, &aio_ret);
    }
    g_assert(acb != NULL);
    g_assert_cmpint(aio_ret, ==, -EINPROGRESS);

    aio_context_release(ctx_a);

    data = (struct test_iothread_data) {
        .bs         = bs,
        .drain_type = drain_type,
        .aio_ret    = &aio_ret,
    };

    switch (drain_thread) {
    case 0:
        if (drain_type != BDRV_DRAIN_ALL) {
            aio_context_acquire(ctx_a);
        }

        aio_bh_schedule_oneshot(ctx_a, test_iothread_main_thread_bh, &data);

        /* The request is running on the IOThread a. Draining its block device
         * will make sure that it has completed as far as the BDS is concerned,
         * but the drain in this thread can continue immediately after
         * bdrv_dec_in_flight() and aio_ret might be assigned only slightly
         * later. */
        qemu_event_reset(&done_event);
        do_drain_begin(drain_type, bs);
        g_assert_cmpint(bs->in_flight, ==, 0);

        if (drain_type != BDRV_DRAIN_ALL) {
            aio_context_release(ctx_a);
        }
        qemu_event_wait(&done_event);
        if (drain_type != BDRV_DRAIN_ALL) {
            aio_context_acquire(ctx_a);
        }

        g_assert_cmpint(aio_ret, ==, 0);
        do_drain_end(drain_type, bs);

        if (drain_type != BDRV_DRAIN_ALL) {
            aio_context_release(ctx_a);
        }
        break;
    case 1:
        qemu_event_reset(&done_event);
        aio_bh_schedule_oneshot(ctx_a, test_iothread_drain_entry, &data);
        qemu_event_wait(&done_event);
        break;
    default:
        g_assert_not_reached();
    }

    aio_context_acquire(ctx_a);
    blk_set_aio_context(blk, qemu_get_aio_context());
    aio_context_release(ctx_a);

    bdrv_unref(bs);
    blk_unref(blk);

out:
    iothread_join(a);
    iothread_join(b);
}

static void test_iothread_drain_all(void)
{
    test_iothread_common(BDRV_DRAIN_ALL, 0);
    test_iothread_common(BDRV_DRAIN_ALL, 1);
}

static void test_iothread_drain(void)
{
    test_iothread_common(BDRV_DRAIN, 0);
    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;
    int run_ret;
    int prepare_ret;
    bool should_complete;
} TestBlockJob;

static int test_job_prepare(Job *job)
{
    TestBlockJob *s = container_of(job, TestBlockJob, common.job);

    /* Provoke an AIO_WAIT_WHILE() call to verify there is no deadlock */
    blk_flush(s->common.blk);
    return s->prepare_ret;
}

static void test_job_commit(Job *job)
{
    TestBlockJob *s = container_of(job, TestBlockJob, common.job);

    /* Provoke an AIO_WAIT_WHILE() call to verify there is no deadlock */
    blk_flush(s->common.blk);
}

static void test_job_abort(Job *job)
{
    TestBlockJob *s = container_of(job, TestBlockJob, common.job);

    /* Provoke an AIO_WAIT_WHILE() call to verify there is no deadlock */
    blk_flush(s->common.blk);
}

static int coroutine_fn test_job_run(Job *job, Error **errp)
{
    TestBlockJob *s = container_of(job, TestBlockJob, common.job);

    job_transition_to_ready(&s->common.job);
    while (!s->should_complete) {
        /* Avoid job_sleep_ns() because it marks the job as !busy. We want to
         * emulate some actual activity (probably some I/O) here so that drain
         * has to wait for this activity to stop. */
        qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 100000);
        job_pause_point(&s->common.job);
    }

    return s->run_ret;
}

static void test_job_complete(Job *job, Error **errp)
{
    TestBlockJob *s = container_of(job, TestBlockJob, common.job);
    s->should_complete = true;
}

BlockJobDriver test_job_driver = {
    .job_driver = {
        .instance_size  = sizeof(TestBlockJob),
        .free           = block_job_free,
        .user_resume    = block_job_user_resume,
        .drain          = block_job_drain,
        .run            = test_job_run,
        .complete       = test_job_complete,
        .prepare        = test_job_prepare,
        .commit         = test_job_commit,
        .abort          = test_job_abort,
    },
};

enum test_job_result {
    TEST_JOB_SUCCESS,
    TEST_JOB_FAIL_RUN,
    TEST_JOB_FAIL_PREPARE,
};

static void test_blockjob_common(enum drain_type drain_type, bool use_iothread,
                                 enum test_job_result result)
{
    BlockBackend *blk_src, *blk_target;
    BlockDriverState *src, *target;
    BlockJob *job;
    TestBlockJob *tjob;
    IOThread *iothread = NULL;
    AioContext *ctx;
    int ret;

    src = bdrv_new_open_driver(&bdrv_test, "source", BDRV_O_RDWR,
                               &error_abort);
    blk_src = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    blk_insert_bs(blk_src, src, &error_abort);

    if (use_iothread) {
        iothread = iothread_new();
        ctx = iothread_get_aio_context(iothread);
        blk_set_aio_context(blk_src, ctx);
    } else {
        ctx = qemu_get_aio_context();
    }

    target = bdrv_new_open_driver(&bdrv_test, "target", BDRV_O_RDWR,
                                  &error_abort);
    blk_target = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    blk_insert_bs(blk_target, target, &error_abort);

    aio_context_acquire(ctx);
    tjob = block_job_create("job0", &test_job_driver, NULL, src,
                            0, BLK_PERM_ALL,
                            0, 0, NULL, NULL, &error_abort);
    job = &tjob->common;
    block_job_add_bdrv(job, "target", target, 0, BLK_PERM_ALL, &error_abort);

    switch (result) {
    case TEST_JOB_SUCCESS:
        break;
    case TEST_JOB_FAIL_RUN:
        tjob->run_ret = -EIO;
        break;
    case TEST_JOB_FAIL_PREPARE:
        tjob->prepare_ret = -EIO;
        break;
    }

    job_start(&job->job);
    aio_context_release(ctx);

    g_assert_cmpint(job->job.pause_count, ==, 0);
    g_assert_false(job->job.paused);
    g_assert_true(job->job.busy); /* We're in qemu_co_sleep_ns() */

    do_drain_begin_unlocked(drain_type, src);

    if (drain_type == BDRV_DRAIN_ALL) {
        /* bdrv_drain_all() drains both src and target */
        g_assert_cmpint(job->job.pause_count, ==, 2);
    } else {
        g_assert_cmpint(job->job.pause_count, ==, 1);
    }
    g_assert_true(job->job.paused);
    g_assert_false(job->job.busy); /* The job is paused */

    do_drain_end_unlocked(drain_type, src);

    if (use_iothread) {
        /* paused is reset in the I/O thread, wait for it */
        while (job->job.paused) {
            aio_poll(qemu_get_aio_context(), false);
        }
    }

    g_assert_cmpint(job->job.pause_count, ==, 0);
    g_assert_false(job->job.paused);
    g_assert_true(job->job.busy); /* We're in qemu_co_sleep_ns() */

    do_drain_begin(drain_type, target);

    if (drain_type == BDRV_DRAIN_ALL) {
        /* bdrv_drain_all() drains both src and target */
        g_assert_cmpint(job->job.pause_count, ==, 2);
    } else {
        g_assert_cmpint(job->job.pause_count, ==, 1);
    }
    g_assert_true(job->job.paused);
    g_assert_false(job->job.busy); /* The job is paused */

    do_drain_end(drain_type, target);

    if (use_iothread) {
        /* paused is reset in the I/O thread, wait for it */
        while (job->job.paused) {
            aio_poll(qemu_get_aio_context(), false);
        }
    }

    g_assert_cmpint(job->job.pause_count, ==, 0);
    g_assert_false(job->job.paused);
    g_assert_true(job->job.busy); /* We're in qemu_co_sleep_ns() */

    aio_context_acquire(ctx);
    ret = job_complete_sync(&job->job, &error_abort);
    g_assert_cmpint(ret, ==, (result == TEST_JOB_SUCCESS ? 0 : -EIO));

    if (use_iothread) {
        blk_set_aio_context(blk_src, qemu_get_aio_context());
    }
    aio_context_release(ctx);

    blk_unref(blk_src);
    blk_unref(blk_target);
    bdrv_unref(src);
    bdrv_unref(target);

    if (iothread) {
        iothread_join(iothread);
    }
}

static void test_blockjob_drain_all(void)
{
    test_blockjob_common(BDRV_DRAIN_ALL, false, TEST_JOB_SUCCESS);
}

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);
    test_blockjob_common(BDRV_DRAIN_ALL, false, TEST_JOB_FAIL_PREPARE);
}

static void test_blockjob_error_drain(void)
{
    test_blockjob_common(BDRV_DRAIN, false, TEST_JOB_FAIL_RUN);
    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);
}

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);
    test_blockjob_common(BDRV_DRAIN_ALL, true, TEST_JOB_FAIL_PREPARE);
}

static void test_blockjob_iothread_error_drain(void)
{
    test_blockjob_common(BDRV_DRAIN, true, TEST_JOB_FAIL_RUN);
    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;
} BDRVTestTopState;

static void bdrv_test_top_close(BlockDriverState *bs)
{
    BdrvChild *c, *next_c;
    QLIST_FOREACH_SAFE(c, &bs->children, next, next_c) {
        bdrv_unref_child(bs, c);
    }
}

static int coroutine_fn bdrv_test_top_co_preadv(BlockDriverState *bs,
                                                uint64_t offset, uint64_t bytes,
                                                QEMUIOVector *qiov, int flags)
{
    BDRVTestTopState *tts = bs->opaque;
    return bdrv_co_preadv(tts->wait_child, offset, bytes, qiov, flags);
}

static BlockDriver bdrv_test_top_driver = {
    .format_name            = "test_top_driver",
    .instance_size          = sizeof(BDRVTestTopState),

    .bdrv_close             = bdrv_test_top_close,
    .bdrv_co_preadv         = bdrv_test_top_co_preadv,

    .bdrv_child_perm        = bdrv_format_default_perms,
};

typedef struct TestCoDeleteByDrainData {
    BlockBackend *blk;
    bool detach_instead_of_delete;
    bool done;
} TestCoDeleteByDrainData;

static void coroutine_fn test_co_delete_by_drain(void *opaque)
{
    TestCoDeleteByDrainData *dbdd = opaque;
    BlockBackend *blk = dbdd->blk;
    BlockDriverState *bs = blk_bs(blk);
    BDRVTestTopState *tts = bs->opaque;
    void *buffer = g_malloc(65536);
    QEMUIOVector qiov;
    struct iovec iov = {
        .iov_base = buffer,
        .iov_len  = 65536,
    };

    qemu_iovec_init_external(&qiov, &iov, 1);

    /* Pretend some internal write operation from parent to child.
     * Important: We have to read from the child, not from the parent!
     * Draining works by first propagating it all up the tree to the
     * root and then waiting for drainage from root to the leaves
     * (protocol nodes).  If we have a request waiting on the root,
     * everything will be drained before we go back down the tree, but
     * we do not want that.  We want to be in the middle of draining
     * when this following requests returns. */
    bdrv_co_preadv(tts->wait_child, 0, 65536, &qiov, 0);

    g_assert_cmpint(bs->refcnt, ==, 1);

    if (!dbdd->detach_instead_of_delete) {
        blk_unref(blk);
    } else {
        BdrvChild *c, *next_c;
        QLIST_FOREACH_SAFE(c, &bs->children, next, next_c) {
            bdrv_unref_child(bs, c);
        }
    }

    dbdd->done = true;
    g_free(buffer);
}

/**
 * Test what happens when some BDS has some children, you drain one of
 * them and this results in the BDS being deleted.
 *
 * If @detach_instead_of_delete is set, the BDS is not going to be
 * deleted but will only detach all of its children.
 */
static void do_test_delete_by_drain(bool detach_instead_of_delete,
                                    enum drain_type drain_type)
{
    BlockBackend *blk;
    BlockDriverState *bs, *child_bs, *null_bs;
    BDRVTestTopState *tts;
    TestCoDeleteByDrainData dbdd;
    Coroutine *co;

    bs = bdrv_new_open_driver(&bdrv_test_top_driver, "top", BDRV_O_RDWR,
                              &error_abort);
    bs->total_sectors = 65536 >> BDRV_SECTOR_BITS;
    tts = bs->opaque;

    null_bs = bdrv_open("null-co://", NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
                        &error_abort);
    bdrv_attach_child(bs, null_bs, "null-child", &child_file, &error_abort);

    /* This child will be the one to pass to requests through to, and
     * it will stall until a drain occurs */
    child_bs = bdrv_new_open_driver(&bdrv_test, "child", BDRV_O_RDWR,
                                    &error_abort);
    child_bs->total_sectors = 65536 >> BDRV_SECTOR_BITS;
    /* Takes our reference to child_bs */
    tts->wait_child = bdrv_attach_child(bs, child_bs, "wait-child", &child_file,
                                        &error_abort);

    /* This child is just there to be deleted
     * (for detach_instead_of_delete == true) */
    null_bs = bdrv_open("null-co://", NULL, NULL, BDRV_O_RDWR | BDRV_O_PROTOCOL,
                        &error_abort);
    bdrv_attach_child(bs, null_bs, "null-child", &child_file, &error_abort);

    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    blk_insert_bs(blk, bs, &error_abort);

    /* Referenced by blk now */
    bdrv_unref(bs);

    g_assert_cmpint(bs->refcnt, ==, 1);
    g_assert_cmpint(child_bs->refcnt, ==, 1);
    g_assert_cmpint(null_bs->refcnt, ==, 1);


    dbdd = (TestCoDeleteByDrainData){
        .blk = blk,
        .detach_instead_of_delete = detach_instead_of_delete,
        .done = false,
    };
    co = qemu_coroutine_create(test_co_delete_by_drain, &dbdd);
    qemu_coroutine_enter(co);

    /* Drain the child while the read operation is still pending.
     * This should result in the operation finishing and
     * test_co_delete_by_drain() resuming.  Thus, @bs will be deleted
     * and the coroutine will exit while this drain operation is still
     * in progress. */
    switch (drain_type) {
    case BDRV_DRAIN:
        bdrv_ref(child_bs);
        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();
        break;
    default:
        g_assert_not_reached();
    }

    while (!dbdd.done) {
        aio_poll(qemu_get_aio_context(), true);
    }

    if (detach_instead_of_delete) {
        /* Here, the reference has not passed over to the coroutine,
         * so we have to delete the BB ourselves */
        blk_unref(blk);
    }
}

static void test_delete_by_drain(void)
{
    do_test_delete_by_drain(false, BDRV_DRAIN);
}

static void test_detach_by_drain_all(void)
{
    do_test_delete_by_drain(true, BDRV_DRAIN_ALL);
}

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;
    BdrvChild *child_b;
    BlockDriverState *c;
    BdrvChild *child_c;
    bool by_parent_cb;
};
static struct detach_by_parent_data detach_by_parent_data;

static void detach_indirect_bh(void *opaque)
{
    struct detach_by_parent_data *data = opaque;

    bdrv_unref_child(data->parent_b, data->child_b);

    bdrv_ref(data->c);
    data->child_c = bdrv_attach_child(data->parent_b, data->c, "PB-C",
                                      &child_file, &error_abort);
}

static void detach_by_parent_aio_cb(void *opaque, int ret)
{
    struct detach_by_parent_data *data = &detach_by_parent_data;

    g_assert_cmpint(ret, ==, 0);
    if (data->by_parent_cb) {
        detach_indirect_bh(data);
    }
}

static void detach_by_driver_cb_drained_begin(BdrvChild *child)
{
    aio_bh_schedule_oneshot(qemu_get_current_aio_context(),
                            detach_indirect_bh, &detach_by_parent_data);
    child_file.drained_begin(child);
}

static BdrvChildRole detach_by_driver_cb_role;

/*
 * Initial graph:
 *
 * PA     PB
 *    \ /   \
 *     A     B     C
 *
 * by_parent_cb == true:  Test that parent callbacks don't poll
 *
 *     PA has a pending write request whose callback changes the child nodes of
 *     PB: It removes B and adds C instead. The subtree of PB is drained, which
 *     will indirectly drain the write request, too.
 *
 * by_parent_cb == false: Test that bdrv_drain_invoke() doesn't poll
 *
 *     PA's BdrvChildRole has a .drained_begin callback that schedules a BH
 *     that does the same graph change. If bdrv_drain_invoke() calls it, the
 *     state is messed up, but if it is only polled in the single
 *     BDRV_POLL_WHILE() at the end of the drain, this should work fine.
 */
static void test_detach_indirect(bool by_parent_cb)
{
    BlockBackend *blk;
    BlockDriverState *parent_a, *parent_b, *a, *b, *c;
    BdrvChild *child_a, *child_b;
    BlockAIOCB *acb;

    QEMUIOVector qiov;
    struct iovec iov = {
        .iov_base = NULL,
        .iov_len = 0,
    };
    qemu_iovec_init_external(&qiov, &iov, 1);

    if (!by_parent_cb) {
        detach_by_driver_cb_role = child_file;
        detach_by_driver_cb_role.drained_begin =
            detach_by_driver_cb_drained_begin;
    }

    /* Create all involved nodes */
    parent_a = bdrv_new_open_driver(&bdrv_test, "parent-a", BDRV_O_RDWR,
                                    &error_abort);
    parent_b = bdrv_new_open_driver(&bdrv_test, "parent-b", 0,
                                    &error_abort);

    a = bdrv_new_open_driver(&bdrv_test, "a", BDRV_O_RDWR, &error_abort);
    b = bdrv_new_open_driver(&bdrv_test, "b", BDRV_O_RDWR, &error_abort);
    c = bdrv_new_open_driver(&bdrv_test, "c", BDRV_O_RDWR, &error_abort);

    /* blk is a BB for parent-a */
    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    blk_insert_bs(blk, parent_a, &error_abort);
    bdrv_unref(parent_a);

    /* If we want to get bdrv_drain_invoke() to call aio_poll(), the driver
     * callback must not return immediately. */
    if (!by_parent_cb) {
        BDRVTestState *s = parent_a->opaque;
        s->sleep_in_drain_begin = true;
    }

    /* Set child relationships */
    bdrv_ref(b);
    bdrv_ref(a);
    child_b = bdrv_attach_child(parent_b, b, "PB-B", &child_file, &error_abort);
    child_a = bdrv_attach_child(parent_b, a, "PB-A", &child_backing, &error_abort);

    bdrv_ref(a);
    bdrv_attach_child(parent_a, a, "PA-A",
                      by_parent_cb ? &child_file : &detach_by_driver_cb_role,
                      &error_abort);

    g_assert_cmpint(parent_a->refcnt, ==, 1);
    g_assert_cmpint(parent_b->refcnt, ==, 1);
    g_assert_cmpint(a->refcnt, ==, 3);
    g_assert_cmpint(b->refcnt, ==, 2);
    g_assert_cmpint(c->refcnt, ==, 1);

    g_assert(QLIST_FIRST(&parent_b->children) == child_a);
    g_assert(QLIST_NEXT(child_a, next) == child_b);
    g_assert(QLIST_NEXT(child_b, next) == NULL);

    /* Start the evil write request */
    detach_by_parent_data = (struct detach_by_parent_data) {
        .parent_b = parent_b,
        .child_b = child_b,
        .c = c,
        .by_parent_cb = by_parent_cb,
    };
    acb = blk_aio_preadv(blk, 0, &qiov, 0, detach_by_parent_aio_cb, NULL);
    g_assert(acb != NULL);

    /* Drain and check the expected result */
    bdrv_subtree_drained_begin(parent_b);

    g_assert(detach_by_parent_data.child_c != NULL);

    g_assert_cmpint(parent_a->refcnt, ==, 1);
    g_assert_cmpint(parent_b->refcnt, ==, 1);
    g_assert_cmpint(a->refcnt, ==, 3);
    g_assert_cmpint(b->refcnt, ==, 1);
    g_assert_cmpint(c->refcnt, ==, 2);

    g_assert(QLIST_FIRST(&parent_b->children) == detach_by_parent_data.child_c);
    g_assert(QLIST_NEXT(detach_by_parent_data.child_c, next) == child_a);
    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(a->quiesce_counter, ==, 1);
    g_assert_cmpint(b->quiesce_counter, ==, 0);
    g_assert_cmpint(c->quiesce_counter, ==, 1);

    bdrv_subtree_drained_end(parent_b);

    bdrv_unref(parent_b);
    blk_unref(blk);

    /* XXX Once bdrv_close() unref's children instead of just detaching them,
     * this won't be necessary any more. */
    bdrv_unref(a);
    bdrv_unref(a);
    bdrv_unref(c);

    g_assert_cmpint(a->refcnt, ==, 1);
    g_assert_cmpint(b->refcnt, ==, 1);
    g_assert_cmpint(c->refcnt, ==, 1);
    bdrv_unref(a);
    bdrv_unref(b);
    bdrv_unref(c);
}

static void test_detach_by_parent_cb(void)
{
    test_detach_indirect(true);
}

static void test_detach_by_driver_cb(void)
{
    test_detach_indirect(false);
}

static void test_append_to_drained(void)
{
    BlockBackend *blk;
    BlockDriverState *base, *overlay;
    BDRVTestState *base_s, *overlay_s;

    blk = blk_new(BLK_PERM_ALL, BLK_PERM_ALL);
    base = bdrv_new_open_driver(&bdrv_test, "base", BDRV_O_RDWR, &error_abort);
    base_s = base->opaque;
    blk_insert_bs(blk, base, &error_abort);

    overlay = bdrv_new_open_driver(&bdrv_test, "overlay", BDRV_O_RDWR,
                                   &error_abort);
    overlay_s = overlay->opaque;

    do_drain_begin(BDRV_DRAIN, base);
    g_assert_cmpint(base->quiesce_counter, ==, 1);
    g_assert_cmpint(base_s->drain_count, ==, 1);
    g_assert_cmpint(base->in_flight, ==, 0);

    /* Takes ownership of overlay, so we don't have to unref it later */
    bdrv_append(overlay, base, &error_abort);
    g_assert_cmpint(base->in_flight, ==, 0);
    g_assert_cmpint(overlay->in_flight, ==, 0);

    g_assert_cmpint(base->quiesce_counter, ==, 1);
    g_assert_cmpint(base_s->drain_count, ==, 1);
    g_assert_cmpint(overlay->quiesce_counter, ==, 1);
    g_assert_cmpint(overlay_s->drain_count, ==, 1);

    do_drain_end(BDRV_DRAIN, base);

    g_assert_cmpint(base->quiesce_counter, ==, 0);
    g_assert_cmpint(base_s->drain_count, ==, 0);
    g_assert_cmpint(overlay->quiesce_counter, ==, 0);
    g_assert_cmpint(overlay_s->drain_count, ==, 0);

    bdrv_unref(base);
    blk_unref(blk);
}

int main(int argc, char **argv)
{
    int ret;

    bdrv_init();
    qemu_init_main_loop(&error_abort);

    g_test_init(&argc, &argv, NULL);
    qemu_event_init(&done_event, false);

    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);

    g_test_add_func("/bdrv-drain/attach/drain", test_append_to_drained);

    ret = g_test_run();
    qemu_event_destroy(&done_event);
    return ret;
}