From: Kevin Wolf <kwolf@redhat.com>
To: qemu-block@nongnu.org
Cc: kwolf@redhat.com, qemu-devel@nongnu.org
Subject: [Qemu-devel] [PULL 09/16] tests: Test polling in bdrv_drop_intermediate()
Date: Fri, 16 Aug 2019 11:34:32 +0200 [thread overview]
Message-ID: <20190816093439.14262-10-kwolf@redhat.com> (raw)
In-Reply-To: <20190816093439.14262-1-kwolf@redhat.com>
From: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
tests/test-bdrv-drain.c | 167 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 167 insertions(+)
diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c
index 03fa1142a1..1600d41e9a 100644
--- a/tests/test-bdrv-drain.c
+++ b/tests/test-bdrv-drain.c
@@ -100,6 +100,13 @@ static void bdrv_test_child_perm(BlockDriverState *bs, BdrvChild *c,
nperm, nshared);
}
+static int bdrv_test_change_backing_file(BlockDriverState *bs,
+ const char *backing_file,
+ const char *backing_fmt)
+{
+ return 0;
+}
+
static BlockDriver bdrv_test = {
.format_name = "test",
.instance_size = sizeof(BDRVTestState),
@@ -111,6 +118,8 @@ static BlockDriver bdrv_test = {
.bdrv_co_drain_end = bdrv_test_co_drain_end,
.bdrv_child_perm = bdrv_test_child_perm,
+
+ .bdrv_change_backing_file = bdrv_test_change_backing_file,
};
static void aio_ret_cb(void *opaque, int ret)
@@ -1671,6 +1680,161 @@ static void test_blockjob_commit_by_drained_end(void)
bdrv_unref(bs_child);
}
+
+typedef struct TestSimpleBlockJob {
+ BlockJob common;
+ bool should_complete;
+ bool *did_complete;
+} TestSimpleBlockJob;
+
+static int coroutine_fn test_simple_job_run(Job *job, Error **errp)
+{
+ TestSimpleBlockJob *s = container_of(job, TestSimpleBlockJob, common.job);
+
+ while (!s->should_complete) {
+ job_sleep_ns(job, 0);
+ }
+
+ return 0;
+}
+
+static void test_simple_job_clean(Job *job)
+{
+ TestSimpleBlockJob *s = container_of(job, TestSimpleBlockJob, common.job);
+ *s->did_complete = true;
+}
+
+static const BlockJobDriver test_simple_job_driver = {
+ .job_driver = {
+ .instance_size = sizeof(TestSimpleBlockJob),
+ .free = block_job_free,
+ .user_resume = block_job_user_resume,
+ .drain = block_job_drain,
+ .run = test_simple_job_run,
+ .clean = test_simple_job_clean,
+ },
+};
+
+static int drop_intermediate_poll_update_filename(BdrvChild *child,
+ BlockDriverState *new_base,
+ const char *filename,
+ Error **errp)
+{
+ /*
+ * We are free to poll here, which may change the block graph, if
+ * it is not drained.
+ */
+
+ /* If the job is not drained: Complete it, schedule job_exit() */
+ aio_poll(qemu_get_current_aio_context(), false);
+ /* If the job is not drained: Run job_exit(), finish the job */
+ aio_poll(qemu_get_current_aio_context(), false);
+
+ return 0;
+}
+
+/**
+ * Test a poll in the midst of bdrv_drop_intermediate().
+ *
+ * bdrv_drop_intermediate() calls BdrvChildRole.update_filename(),
+ * which can yield or poll. This may lead to graph changes, unless
+ * the whole subtree in question is drained.
+ *
+ * We test this on the following graph:
+ *
+ * Job
+ *
+ * |
+ * job-node
+ * |
+ * v
+ *
+ * job-node
+ *
+ * |
+ * backing
+ * |
+ * v
+ *
+ * node-2 --chain--> node-1 --chain--> node-0
+ *
+ * We drop node-1 with bdrv_drop_intermediate(top=node-1, base=node-0).
+ *
+ * This first updates node-2's backing filename by invoking
+ * drop_intermediate_poll_update_filename(), which polls twice. This
+ * causes the job to finish, which in turns causes the job-node to be
+ * deleted.
+ *
+ * bdrv_drop_intermediate() uses a QLIST_FOREACH_SAFE() loop, so it
+ * already has a pointer to the BdrvChild edge between job-node and
+ * node-1. When it tries to handle that edge, we probably get a
+ * segmentation fault because the object no longer exists.
+ *
+ *
+ * The solution is for bdrv_drop_intermediate() to drain top's
+ * subtree. This prevents graph changes from happening just because
+ * BdrvChildRole.update_filename() yields or polls. Thus, the block
+ * job is paused during that drained section and must finish before or
+ * after.
+ *
+ * (In addition, bdrv_replace_child() must keep the job paused.)
+ */
+static void test_drop_intermediate_poll(void)
+{
+ static BdrvChildRole chain_child_role;
+ BlockDriverState *chain[3];
+ TestSimpleBlockJob *job;
+ BlockDriverState *job_node;
+ bool job_has_completed = false;
+ int i;
+ int ret;
+
+ chain_child_role = child_backing;
+ chain_child_role.update_filename = drop_intermediate_poll_update_filename;
+
+ for (i = 0; i < 3; i++) {
+ char name[32];
+ snprintf(name, 32, "node-%i", i);
+
+ chain[i] = bdrv_new_open_driver(&bdrv_test, name, 0, &error_abort);
+ }
+
+ job_node = bdrv_new_open_driver(&bdrv_test, "job-node", BDRV_O_RDWR,
+ &error_abort);
+ bdrv_set_backing_hd(job_node, chain[1], &error_abort);
+
+ /*
+ * Establish the chain last, so the chain links are the first
+ * elements in the BDS.parents lists
+ */
+ for (i = 0; i < 3; i++) {
+ if (i) {
+ /* Takes the reference to chain[i - 1] */
+ chain[i]->backing = bdrv_attach_child(chain[i], chain[i - 1],
+ "chain", &chain_child_role,
+ &error_abort);
+ }
+ }
+
+ job = block_job_create("job", &test_simple_job_driver, NULL, job_node,
+ 0, BLK_PERM_ALL, 0, 0, NULL, NULL, &error_abort);
+
+ /* The job has a reference now */
+ bdrv_unref(job_node);
+
+ job->did_complete = &job_has_completed;
+
+ job_start(&job->common.job);
+ job->should_complete = true;
+
+ g_assert(!job_has_completed);
+ ret = bdrv_drop_intermediate(chain[1], chain[0], NULL);
+ g_assert(ret == 0);
+ g_assert(job_has_completed);
+
+ bdrv_unref(chain[2]);
+}
+
int main(int argc, char **argv)
{
int ret;
@@ -1757,6 +1921,9 @@ int main(int argc, char **argv)
g_test_add_func("/bdrv-drain/blockjob/commit_by_drained_end",
test_blockjob_commit_by_drained_end);
+ g_test_add_func("/bdrv-drain/bdrv_drop_intermediate/poll",
+ test_drop_intermediate_poll);
+
ret = g_test_run();
qemu_event_destroy(&done_event);
return ret;
--
2.20.1
next prev parent reply other threads:[~2019-08-16 9:46 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 9:34 [Qemu-devel] [PULL 00/16] Block layer patches Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 01/16] iotests/118: Test media change for scsi-cd Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 02/16] iotests/118: Create test classes dynamically Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 03/16] iotests/118: Add -blockdev based tests Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 04/16] iotests: Move migration helpers to iotests.py Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 05/16] iotests: Test migration with all kinds of filter nodes Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 06/16] block: Simplify bdrv_filter_default_perms() Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 07/16] block: Keep subtree drained in drop_intermediate Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 08/16] block: Reduce (un)drains when replacing a child Kevin Wolf
2019-08-16 9:34 ` Kevin Wolf [this message]
2019-08-16 9:34 ` [Qemu-devel] [PULL 10/16] tests: Test mid-drain bdrv_replace_child_noperm() Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 11/16] iotests: Add test for concurrent stream/commit Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 12/16] block: Remove blk_pread_unthrottled() Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 13/16] mirror: Keep mirror_top_bs drained after dropping permissions Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 14/16] block-backend: Queue requests while drained Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 15/16] qemu-img convert: Deprecate using -n and -o together Kevin Wolf
2019-08-16 9:34 ` [Qemu-devel] [PULL 16/16] file-posix: Handle undetectable alignment Kevin Wolf
2019-08-16 10:14 ` [Qemu-devel] [PULL 00/16] Block layer patches no-reply
2019-08-16 16:21 ` Peter Maydell
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