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From 74105e9b2d948c03786e0f86f116d5e410e8d1c6 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Wed, 10 Oct 2018 20:21:44 +0100
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Subject: [PATCH 18/49] test-bdrv-drain: Test that bdrv_drain_invoke() doesn't
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 poll
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20181010202213.7372-6-kwolf@redhat.com>
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Patchwork-id: 82593
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O-Subject: [RHEL-8 qemu-kvm PATCH 15/44] test-bdrv-drain: Test that bdrv_drain_invoke() doesn't poll
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Bugzilla: 1637976
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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This adds a test case that goes wrong if bdrv_drain_invoke() calls
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aio_poll().
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 57320ca961c2e8488e1884b4ebbcb929b6901dc6)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 tests/test-bdrv-drain.c | 102 +++++++++++++++++++++++++++++++++++++++++-------
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 1 file changed, 88 insertions(+), 14 deletions(-)
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diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c
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index f786326..c4aa913 100644
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--- a/tests/test-bdrv-drain.c
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+++ b/tests/test-bdrv-drain.c
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@@ -34,12 +34,16 @@ static QemuEvent done_event;
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 typedef struct BDRVTestState {
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     int drain_count;
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     AioContext *bh_indirection_ctx;
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+    bool sleep_in_drain_begin;
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 } BDRVTestState;
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 static void coroutine_fn bdrv_test_co_drain_begin(BlockDriverState *bs)
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 {
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     BDRVTestState *s = bs->opaque;
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     s->drain_count++;
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+    if (s->sleep_in_drain_begin) {
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+        qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 100000);
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+    }
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 }
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 static void coroutine_fn bdrv_test_co_drain_end(BlockDriverState *bs)
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@@ -80,6 +84,22 @@ static int coroutine_fn bdrv_test_co_preadv(BlockDriverState *bs,
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     return 0;
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 }
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+static void bdrv_test_child_perm(BlockDriverState *bs, BdrvChild *c,
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+                                 const BdrvChildRole *role,
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+                                 BlockReopenQueue *reopen_queue,
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+                                 uint64_t perm, uint64_t shared,
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+                                 uint64_t *nperm, uint64_t *nshared)
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+{
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+    /* bdrv_format_default_perms() accepts only these two, so disguise
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+     * detach_by_driver_cb_role as one of them. */
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+    if (role != &child_file && role != &child_backing) {
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+        role = &child_file;
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+    }
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+
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+    bdrv_format_default_perms(bs, c, role, reopen_queue, perm, shared,
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+                              nperm, nshared);
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+}
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+
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 static BlockDriver bdrv_test = {
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     .format_name            = "test",
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     .instance_size          = sizeof(BDRVTestState),
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@@ -90,7 +110,7 @@ static BlockDriver bdrv_test = {
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     .bdrv_co_drain_begin    = bdrv_test_co_drain_begin,
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     .bdrv_co_drain_end      = bdrv_test_co_drain_end,
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-    .bdrv_child_perm        = bdrv_format_default_perms,
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+    .bdrv_child_perm        = bdrv_test_child_perm,
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 };
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 static void aio_ret_cb(void *opaque, int ret)
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@@ -982,13 +1002,14 @@ struct detach_by_parent_data {
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     BdrvChild *child_b;
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     BlockDriverState *c;
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     BdrvChild *child_c;
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+    bool by_parent_cb;
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 };
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+static struct detach_by_parent_data detach_by_parent_data;
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-static void detach_by_parent_aio_cb(void *opaque, int ret)
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+static void detach_indirect_bh(void *opaque)
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 {
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     struct detach_by_parent_data *data = opaque;
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-    g_assert_cmpint(ret, ==, 0);
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     bdrv_unref_child(data->parent_b, data->child_b);
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     bdrv_ref(data->c);
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@@ -996,6 +1017,25 @@ static void detach_by_parent_aio_cb(void *opaque, int ret)
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                                       &child_file, &error_abort);
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 }
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+static void detach_by_parent_aio_cb(void *opaque, int ret)
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+{
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+    struct detach_by_parent_data *data = &detach_by_parent_data;
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+
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+    g_assert_cmpint(ret, ==, 0);
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+    if (data->by_parent_cb) {
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+        detach_indirect_bh(data);
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+    }
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+}
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+
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+static void detach_by_driver_cb_drained_begin(BdrvChild *child)
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+{
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+    aio_bh_schedule_oneshot(qemu_get_current_aio_context(),
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+                            detach_indirect_bh, &detach_by_parent_data);
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+    child_file.drained_begin(child);
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+}
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+
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+static BdrvChildRole detach_by_driver_cb_role;
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+
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 /*
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  * Initial graph:
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  *
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@@ -1003,17 +1043,25 @@ static void detach_by_parent_aio_cb(void *opaque, int ret)
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  *    \ /   \
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  *     A     B     C
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  *
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- * PA has a pending write request whose callback changes the child nodes of PB:
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- * It removes B and adds C instead. The subtree of PB is drained, which will
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- * indirectly drain the write request, too.
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+ * by_parent_cb == true:  Test that parent callbacks don't poll
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+ *
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+ *     PA has a pending write request whose callback changes the child nodes of
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+ *     PB: It removes B and adds C instead. The subtree of PB is drained, which
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+ *     will indirectly drain the write request, too.
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+ *
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+ * by_parent_cb == false: Test that bdrv_drain_invoke() doesn't poll
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+ *
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+ *     PA's BdrvChildRole has a .drained_begin callback that schedules a BH
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+ *     that does the same graph change. If bdrv_drain_invoke() calls it, the
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+ *     state is messed up, but if it is only polled in the single
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+ *     BDRV_POLL_WHILE() at the end of the drain, this should work fine.
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  */
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-static void test_detach_by_parent_cb(void)
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+static void test_detach_indirect(bool by_parent_cb)
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 {
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     BlockBackend *blk;
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     BlockDriverState *parent_a, *parent_b, *a, *b, *c;
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     BdrvChild *child_a, *child_b;
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     BlockAIOCB *acb;
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-    struct detach_by_parent_data data;
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     QEMUIOVector qiov;
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     struct iovec iov = {
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@@ -1022,6 +1070,12 @@ static void test_detach_by_parent_cb(void)
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     };
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     qemu_iovec_init_external(&qiov, &iov, 1);
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+    if (!by_parent_cb) {
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+        detach_by_driver_cb_role = child_file;
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+        detach_by_driver_cb_role.drained_begin =
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+            detach_by_driver_cb_drained_begin;
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+    }
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+
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     /* Create all involved nodes */
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     parent_a = bdrv_new_open_driver(&bdrv_test, "parent-a", BDRV_O_RDWR,
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                                     &error_abort);
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@@ -1037,6 +1091,13 @@ static void test_detach_by_parent_cb(void)
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     blk_insert_bs(blk, parent_a, &error_abort);
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     bdrv_unref(parent_a);
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+    /* If we want to get bdrv_drain_invoke() to call aio_poll(), the driver
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+     * callback must not return immediately. */
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+    if (!by_parent_cb) {
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+        BDRVTestState *s = parent_a->opaque;
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+        s->sleep_in_drain_begin = true;
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+    }
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+
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     /* Set child relationships */
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     bdrv_ref(b);
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     bdrv_ref(a);
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@@ -1044,7 +1105,9 @@ static void test_detach_by_parent_cb(void)
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     child_a = bdrv_attach_child(parent_b, a, "PB-A", &child_backing, &error_abort);
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     bdrv_ref(a);
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-    bdrv_attach_child(parent_a, a, "PA-A", &child_file, &error_abort);
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+    bdrv_attach_child(parent_a, a, "PA-A",
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+                      by_parent_cb ? &child_file : &detach_by_driver_cb_role,
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+                      &error_abort);
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     g_assert_cmpint(parent_a->refcnt, ==, 1);
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     g_assert_cmpint(parent_b->refcnt, ==, 1);
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@@ -1057,18 +1120,19 @@ static void test_detach_by_parent_cb(void)
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     g_assert(QLIST_NEXT(child_b, next) == NULL);
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     /* Start the evil write request */
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-    data = (struct detach_by_parent_data) {
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+    detach_by_parent_data = (struct detach_by_parent_data) {
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         .parent_b = parent_b,
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         .child_b = child_b,
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         .c = c,
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+        .by_parent_cb = by_parent_cb,
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     };
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-    acb = blk_aio_preadv(blk, 0, &qiov, 0, detach_by_parent_aio_cb, &data);
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+    acb = blk_aio_preadv(blk, 0, &qiov, 0, detach_by_parent_aio_cb, NULL);
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     g_assert(acb != NULL);
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     /* Drain and check the expected result */
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     bdrv_subtree_drained_begin(parent_b);
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-    g_assert(data.child_c != NULL);
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+    g_assert(detach_by_parent_data.child_c != NULL);
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     g_assert_cmpint(parent_a->refcnt, ==, 1);
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     g_assert_cmpint(parent_b->refcnt, ==, 1);
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@@ -1076,8 +1140,8 @@ static void test_detach_by_parent_cb(void)
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     g_assert_cmpint(b->refcnt, ==, 1);
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     g_assert_cmpint(c->refcnt, ==, 2);
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-    g_assert(QLIST_FIRST(&parent_b->children) == data.child_c);
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-    g_assert(QLIST_NEXT(data.child_c, next) == child_a);
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+    g_assert(QLIST_FIRST(&parent_b->children) == detach_by_parent_data.child_c);
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+    g_assert(QLIST_NEXT(detach_by_parent_data.child_c, next) == child_a);
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     g_assert(QLIST_NEXT(child_a, next) == NULL);
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     g_assert_cmpint(parent_a->quiesce_counter, ==, 1);
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@@ -1105,6 +1169,15 @@ static void test_detach_by_parent_cb(void)
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     bdrv_unref(c);
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 }
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+static void test_detach_by_parent_cb(void)
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+{
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+    test_detach_indirect(true);
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+}
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+
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+static void test_detach_by_driver_cb(void)
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+{
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+    test_detach_indirect(false);
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+}
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 int main(int argc, char **argv)
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 {
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@@ -1157,6 +1230,7 @@ int main(int argc, char **argv)
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     g_test_add_func("/bdrv-drain/detach/drain", test_detach_by_drain);
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     g_test_add_func("/bdrv-drain/detach/drain_subtree", test_detach_by_drain_subtree);
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     g_test_add_func("/bdrv-drain/detach/parent_cb", test_detach_by_parent_cb);
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+    g_test_add_func("/bdrv-drain/detach/driver_cb", test_detach_by_driver_cb);
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     ret = g_test_run();
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     qemu_event_destroy(&done_event);
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-- 
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1.8.3.1
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