OpenE2K/qemu-e2k
13
4
Fork 0
Code Issues 4 Pull Requests Projects 2 Releases Activity

test-bdrv-drain: bdrv_drain() works with cross-AioContext events

Browse Source 
As long as nobody keeps the other I/O thread from working, there is no
reason why bdrv_drain() wouldn't work with cross-AioContext events. The
key is that the root request we're waiting for is in the AioContext
we're polling (which it always is for bdrv_drain()) so that aio_poll()
is woken up in the end.

Add a test case that shows that it works. Remove the comment in
bdrv_drain() that claims otherwise.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2017-12-10 00:11:13 +01:00
parent 2ef2f16781
commit bb67568954
2 changed files with 186 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
block/io.c
View File

@ -370,10 +370,6 @@ void bdrv_unapply_subtree_drain(BdrvChild *child, BlockDriverState *old_parent)
*
* Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
* AioContext.
*
* Only this BlockDriverState's AioContext is run, so in-flight requests must
* not depend on events in other AioContexts. In that case, use
* bdrv_drain_all() instead.
*/
void coroutine_fn bdrv_co_drain(BlockDriverState *bs)
{

187
tests/test-bdrv-drain.c
View File

@ -27,9 +27,13 @@
#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;
} BDRVTestState;
static void coroutine_fn bdrv_test_co_drain_begin(BlockDriverState *bs)
@ -50,16 +54,29 @@ static void bdrv_test_close(BlockDriverState *bs)
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;
}
@ -490,6 +507,164 @@ static void test_graph_change(void)
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);
}
/*
* 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);
}
/* 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;
@ -618,10 +793,13 @@ static void test_blockjob_drain_subtree(void)
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);
@ -648,10 +826,17 @@ int main(int argc, char **argv)
g_test_add_func("/bdrv-drain/multiparent", test_multiparent);
g_test_add_func("/bdrv-drain/graph-change", test_graph_change);
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);
return g_test_run();
ret = g_test_run();
qemu_event_destroy(&done_event);
return ret;
}