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block: drain from main loop thread in bdrv_co_yield_to_drain()

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For simplicity, always run BlockDevOps .drained_begin/end/poll()
callbacks in the main loop thread. This makes it easier to implement the
callbacks and avoids extra locks.

Move the function pointer declarations from the I/O Code section to the
Global State section for BlockDevOps, BdrvChildClass, and BlockDriver.

Narrow IO_OR_GS_CODE() to GLOBAL_STATE_CODE() where appropriate.

The test-bdrv-drain test case calls bdrv_drain() from an IOThread. This
is now only allowed from coroutine context, so update the test case to
run in a coroutine.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230516190238.8401-11-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-05-16 15:02:28 -04:00 committed by Kevin Wolf
parent ff82b7835b
commit ab61335025
4 changed files with 67 additions and 58 deletions
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14
block/io.c
View File

@ -60,7 +60,7 @@ static void bdrv_parent_drained_begin(BlockDriverState *bs, BdrvChild *ignore)
void bdrv_parent_drained_end_single(BdrvChild *c)
{
IO_OR_GS_CODE();
GLOBAL_STATE_CODE();
assert(c->quiesced_parent);
c->quiesced_parent = false;
@ -108,7 +108,7 @@ static bool bdrv_parent_drained_poll(BlockDriverState *bs, BdrvChild *ignore,
void bdrv_parent_drained_begin_single(BdrvChild *c)
{
IO_OR_GS_CODE();
GLOBAL_STATE_CODE();
assert(!c->quiesced_parent);
c->quiesced_parent = true;
@ -247,7 +247,7 @@ typedef struct {
bool bdrv_drain_poll(BlockDriverState *bs, BdrvChild *ignore_parent,
bool ignore_bds_parents)
{
IO_OR_GS_CODE();
GLOBAL_STATE_CODE();
if (bdrv_parent_drained_poll(bs, ignore_parent, ignore_bds_parents)) {
return true;
@ -334,7 +334,8 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
if (ctx != co_ctx) {
aio_context_release(ctx);
}
replay_bh_schedule_oneshot_event(ctx, bdrv_co_drain_bh_cb, &data);
replay_bh_schedule_oneshot_event(qemu_get_aio_context(),
bdrv_co_drain_bh_cb, &data);
qemu_coroutine_yield();
/* If we are resumed from some other event (such as an aio completion or a
@ -357,6 +358,8 @@ static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
return;
}
GLOBAL_STATE_CODE();
/* Stop things in parent-to-child order */
if (qatomic_fetch_inc(&bs->quiesce_counter) == 0) {
aio_disable_external(bdrv_get_aio_context(bs));
@ -399,11 +402,14 @@ static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent)
{
int old_quiesce_counter;
IO_OR_GS_CODE();
if (qemu_in_coroutine()) {
bdrv_co_yield_to_drain(bs, false, parent, false);
return;
}
assert(bs->quiesce_counter > 0);
GLOBAL_STATE_CODE();
/* Re-enable things in child-to-parent order */
old_quiesce_counter = qatomic_fetch_dec(&bs->quiesce_counter);

72
include/block/block_int-common.h
View File

@ -363,6 +363,21 @@ struct BlockDriver {
void (*bdrv_attach_aio_context)(BlockDriverState *bs,
AioContext *new_context);
/**
* bdrv_drain_begin is called if implemented in the beginning of a
* drain operation to drain and stop any internal sources of requests in
* the driver.
* bdrv_drain_end is called if implemented at the end of the drain.
*
* They should be used by the driver to e.g. manage scheduled I/O
* requests, or toggle an internal state. After the end of the drain new
* requests will continue normally.
*
* Implementations of both functions must not call aio_poll().
*/
void (*bdrv_drain_begin)(BlockDriverState *bs);
void (*bdrv_drain_end)(BlockDriverState *bs);
/**
* Try to get @bs's logical and physical block size.
* On success, store them in @bsz and return zero.
@ -758,21 +773,6 @@ struct BlockDriver {
void coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_io_unplug)(
BlockDriverState *bs);
/**
* bdrv_drain_begin is called if implemented in the beginning of a
* drain operation to drain and stop any internal sources of requests in
* the driver.
* bdrv_drain_end is called if implemented at the end of the drain.
*
* They should be used by the driver to e.g. manage scheduled I/O
* requests, or toggle an internal state. After the end of the drain new
* requests will continue normally.
*
* Implementations of both functions must not call aio_poll().
*/
void (*bdrv_drain_begin)(BlockDriverState *bs);
void (*bdrv_drain_end)(BlockDriverState *bs);
bool (*bdrv_supports_persistent_dirty_bitmap)(BlockDriverState *bs);
bool coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_can_store_new_dirty_bitmap)(
@ -955,6 +955,27 @@ struct BdrvChildClass {
void GRAPH_WRLOCK_PTR (*attach)(BdrvChild *child);
void GRAPH_WRLOCK_PTR (*detach)(BdrvChild *child);
/*
* If this pair of functions is implemented, the parent doesn't issue new
* requests after returning from .drained_begin() until .drained_end() is
* called.
*
* These functions must not change the graph (and therefore also must not
* call aio_poll(), which could change the graph indirectly).
*
* Note that this can be nested. If drained_begin() was called twice, new
* I/O is allowed only after drained_end() was called twice, too.
*/
void (*drained_begin)(BdrvChild *child);
void (*drained_end)(BdrvChild *child);
/*
* Returns whether the parent has pending requests for the child. This
* callback is polled after .drained_begin() has been called until all
* activity on the child has stopped.
*/
bool (*drained_poll)(BdrvChild *child);
/*
* Notifies the parent that the filename of its child has changed (e.g.
* because the direct child was removed from the backing chain), so that it
@ -984,27 +1005,6 @@ struct BdrvChildClass {
const char *(*get_name)(BdrvChild *child);
AioContext *(*get_parent_aio_context)(BdrvChild *child);
/*
* If this pair of functions is implemented, the parent doesn't issue new
* requests after returning from .drained_begin() until .drained_end() is
* called.
*
* These functions must not change the graph (and therefore also must not
* call aio_poll(), which could change the graph indirectly).
*
* Note that this can be nested. If drained_begin() was called twice, new
* I/O is allowed only after drained_end() was called twice, too.
*/
void (*drained_begin)(BdrvChild *child);
void (*drained_end)(BdrvChild *child);
/*
* Returns whether the parent has pending requests for the child. This
* callback is polled after .drained_begin() has been called until all
* activity on the child has stopped.
*/
bool (*drained_poll)(BdrvChild *child);
};
extern const BdrvChildClass child_of_bds;

25
include/sysemu/block-backend-common.h
View File

@ -59,6 +59,19 @@ typedef struct BlockDevOps {
*/
bool (*is_medium_locked)(void *opaque);
/*
* Runs when the backend receives a drain request.
*/
void (*drained_begin)(void *opaque);
/*
* Runs when the backend's last drain request ends.
*/
void (*drained_end)(void *opaque);
/*
* Is the device still busy?
*/
bool (*drained_poll)(void *opaque);
/*
* I/O API functions. These functions are thread-safe.
*
@ -76,18 +89,6 @@ typedef struct BlockDevOps {
* Runs when the size changed (e.g. monitor command block_resize)
*/
void (*resize_cb)(void *opaque);
/*
* Runs when the backend receives a drain request.
*/
void (*drained_begin)(void *opaque);
/*
* Runs when the backend's last drain request ends.
*/
void (*drained_end)(void *opaque);
/*
* Is the device still busy?
*/
bool (*drained_poll)(void *opaque);
} BlockDevOps;
/*

14
tests/unit/test-bdrv-drain.c
View File

@ -483,19 +483,19 @@ struct test_iothread_data {
BlockDriverState *bs;
enum drain_type drain_type;
int *aio_ret;
bool co_done;
};
static void test_iothread_drain_entry(void *opaque)
static void coroutine_fn test_iothread_drain_co_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);
data->co_done = true;
aio_wait_kick();
}
static void test_iothread_aio_cb(void *opaque, int ret)
@ -531,6 +531,7 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
BlockDriverState *bs;
BDRVTestState *s;
BlockAIOCB *acb;
Coroutine *co;
int aio_ret;
struct test_iothread_data data;
@ -609,8 +610,9 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
}
break;
case 1:
aio_bh_schedule_oneshot(ctx_a, test_iothread_drain_entry, &data);
qemu_event_wait(&done_event);
co = qemu_coroutine_create(test_iothread_drain_co_entry, &data);
aio_co_enter(ctx_a, co);
AIO_WAIT_WHILE_UNLOCKED(NULL, !data.co_done);
break;
default:
g_assert_not_reached();