1 files changed, 169 insertions, 0 deletions

diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c
index 22d31c953e..e8a5515b08 100644
--- a/tests/test-bdrv-drain.c
+++ b/tests/test-bdrv-drain.c
@@ -797,6 +797,172 @@ static void test_blockjob_drain_subtree(void)
     test_blockjob_common(BDRV_SUBTREE_DRAIN);
 }
 
+
+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;
+}
+
+/**
+ * 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)
+{
+    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. */
+    bdrv_ref(child_bs);
+    bdrv_drain(child_bs);
+    bdrv_unref(child_bs);
+
+    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);
+}
+
+static void test_detach_by_drain(void)
+{
+    do_test_delete_by_drain(true);
+}
+
+
 int main(int argc, char **argv)
 {
     int ret;
@@ -844,6 +1010,9 @@ int main(int argc, char **argv)
     g_test_add_func("/bdrv-drain/blockjob/drain_subtree",
                     test_blockjob_drain_subtree);
 
+    g_test_add_func("/bdrv-drain/deletion", test_delete_by_drain);
+    g_test_add_func("/bdrv-drain/detach", test_detach_by_drain);
+
     ret = g_test_run();
     qemu_event_destroy(&done_event);
     return ret;