On Sat, Mar 08, 2025 at 06:16:17PM +0800, zoudongjie wrote:
> From: Zhu Yangyang <zhuyangyan...@huawei.com>
>
> The bdrv_drained_begin() function is a blocking function. In scenarios where
> network storage
> is used and network links fail, it may block for a long time.
> Therefore, we add a timeout parameter to control the duration of the block.
>
> Since bdrv_drained_begin() has been widely adopted, both bdrv_drained_begin()
> and bdrv_drained_begin_timeout() will be retained.
>
> Signed-off-by: Zhu Yangyang <zhuyangyan...@huawei.com>
> ---
> block/io.c | 55 ++++++++++++++++++++++++++++++-------
> include/block/aio-wait.h | 58 ++++++++++++++++++++++++++++++++++++++++
> include/block/block-io.h | 7 +++++
> util/aio-wait.c | 7 +++++
> 4 files changed, 117 insertions(+), 10 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index d369b994df..03b8b2dca7 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -255,6 +255,8 @@ typedef struct {
> bool begin;
> bool poll;
> BdrvChild *parent;
> + int ret;
> + int64_t timeout;
Please put the units (milliseconds) into the variable name here and
everywhere else in the patch to avoid confusion about units:
int64_t timeout_ms;
> } BdrvCoDrainData;
>
> /* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */
> @@ -283,6 +285,8 @@ static bool bdrv_drain_poll_top_level(BlockDriverState
> *bs,
> return bdrv_drain_poll(bs, ignore_parent, false);
> }
>
> +static int bdrv_do_drained_begin_timeout(BlockDriverState *bs,
> + BdrvChild *parent, bool poll, int64_t timeout);
> static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
> bool poll);
> static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent);
> @@ -296,7 +300,8 @@ static void bdrv_co_drain_bh_cb(void *opaque)
> if (bs) {
> bdrv_dec_in_flight(bs);
> if (data->begin) {
> - bdrv_do_drained_begin(bs, data->parent, data->poll);
> + data->ret = bdrv_do_drained_begin_timeout(
> + bs, data->parent, data->poll, data->timeout);
> } else {
> assert(!data->poll);
> bdrv_do_drained_end(bs, data->parent);
> @@ -310,10 +315,11 @@ static void bdrv_co_drain_bh_cb(void *opaque)
> aio_co_wake(co);
> }
>
> -static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
> - bool begin,
> - BdrvChild *parent,
> - bool poll)
> +static int coroutine_fn bdrv_co_yield_to_drain_timeout(BlockDriverState *bs,
> + bool begin,
> + BdrvChild *parent,
> + bool poll,
> + int64_t timeout)
> {
> BdrvCoDrainData data;
> Coroutine *self = qemu_coroutine_self();
> @@ -329,6 +335,8 @@ static void coroutine_fn
> bdrv_co_yield_to_drain(BlockDriverState *bs,
> .begin = begin,
> .parent = parent,
> .poll = poll,
> + .timeout = timeout,
> + .ret = 0
> };
>
> if (bs) {
> @@ -342,16 +350,25 @@ static void coroutine_fn
> bdrv_co_yield_to_drain(BlockDriverState *bs,
> /* If we are resumed from some other event (such as an aio completion or
> a
> * timer callback), it is a bug in the caller that should be fixed. */
> assert(data.done);
> + return data.ret;
> }
>
> -static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
> - bool poll)
> +static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
> + bool begin,
> + BdrvChild *parent,
> + bool poll)
> +{
> + bdrv_co_yield_to_drain_timeout(bs, begin, parent, poll, -1);
Is this safe on 32-bit platforms?
> +}
> +
> +static int bdrv_do_drained_begin_timeout(BlockDriverState *bs,
> + BdrvChild *parent, bool poll, int64_t timeout_ms)
> {
> IO_OR_GS_CODE();
>
> if (qemu_in_coroutine()) {
> - bdrv_co_yield_to_drain(bs, true, parent, poll);
> - return;
> + return bdrv_co_yield_to_drain_timeout(bs, true, parent, poll,
> + timeout_ms);
> }
>
> GLOBAL_STATE_CODE();
> @@ -375,8 +392,20 @@ static void bdrv_do_drained_begin(BlockDriverState *bs,
> BdrvChild *parent,
> * nodes.
> */
> if (poll) {
> - BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
> + if (timeout_ms < 0) {
> + BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
> + } else {
> + return BDRV_POLL_WHILE_TIMEOUT(
> + bs, bdrv_drain_poll_top_level(bs, parent), timeout_ms);
> + }
Any reason to handle timeout_ms < 0 here instead of in
BDRV_POLL_WHILE_TIMEOUT()? It would be more consistent to support -1 in
BDRV_POLL_WHILE_TIMEOUT() so that you don't need to remember which
functions/macros support timeout_ms=-1 and which dont.
> }
> + return 0;
> +}
> +
> +static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
> + bool poll)
> +{
> + bdrv_do_drained_begin_timeout(bs, parent, poll, -1);
> }
>
> void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, BdrvChild *parent)
> @@ -390,6 +419,12 @@ bdrv_drained_begin(BlockDriverState *bs)
> IO_OR_GS_CODE();
> bdrv_do_drained_begin(bs, NULL, true);
> }
> +int coroutine_mixed_fn
> +bdrv_drained_begin_timeout(BlockDriverState *bs, int64_t timeout_ms)
> +{
> + IO_OR_GS_CODE();
> + return bdrv_do_drained_begin_timeout(bs, NULL, true, timeout_ms);
> +}
>
> /**
> * This function does not poll, nor must any of its recursively called
> diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
> index cf5e8bde1c..efbcb9777a 100644
> --- a/include/block/aio-wait.h
> +++ b/include/block/aio-wait.h
> @@ -28,6 +28,8 @@
> #include "block/aio.h"
> #include "qemu/main-loop.h"
>
> +#define AIO_WAIT_INTERVAL 10 /* ms */
> +
> /**
> * AioWait:
> *
> @@ -56,6 +58,11 @@ typedef struct {
> unsigned num_waiters;
> } AioWait;
>
> +typedef struct {
> + struct QEMUTimer *timer;
struct is not necessary since QEMUTimer is a typedef:
QEMUTimer *timer;
Also, can this be a struct field instead of a pointer by using
aio_timer_init_ms() instead of aio_timer_new()?
> + int64_t interval;
> +} AioWaitTimer;
> +
> extern AioWait global_aio_wait;
>
> /**
> @@ -99,6 +106,55 @@ extern AioWait global_aio_wait;
> qatomic_dec(&wait_->num_waiters); \
> waited_; })
>
> +/**
> + * AIO_WAIT_WHILE_TIMEOUT:
> + *
> + * Refer to the implementation of AIO_WAIT_WHILE_INTERNAL,
> + * the timeout parameter is added.
> + */
> +#define AIO_WAIT_WHILE_TIMEOUT(ctx, cond, timeout) ({ \
> + int ret_ = 0; \
> + AioWait *wait_ = &global_aio_wait; \
> + AioContext *ctx_ = (ctx); \
> + int64_t start_ = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); \
> + int64_t deadline_ = start_ + (timeout); \
> + /* Ensure that the aio_poll exits periodically to check timeout. */ \
> + AioWaitTimer *s_ = g_malloc0(sizeof(AioWaitTimer)); \
Can this be allocated on the stack instead of the heap?
> + s_->interval = AIO_WAIT_INTERVAL; \
> + /* Increment wait_->num_waiters before evaluating cond. */ \
> + qatomic_inc(&wait_->num_waiters); \
> + /* Paired with smp_mb in aio_wait_kick(). */ \
> + smp_mb__after_rmw(); \
> + if (ctx_ && in_aio_context_home_thread(ctx_)) { \
> + s_->timer = aio_timer_new(ctx_, QEMU_CLOCK_REALTIME, \
> + SCALE_MS, aio_wait_timer_retry, s_); \
> + aio_wait_timer_retry(s_); \
> + while ((cond)) { \
> + aio_poll(ctx_, true); \
> + if (qemu_clock_get_ms(QEMU_CLOCK_REALTIME) > deadline_) { \
> + ret_ = -ETIMEDOUT; \
> + break; \
> + } \
> + } \
What is the purpose of interval?
I expected the timer's callback function to be an empty function that is
called when the deadline expires. The while loop here would use
timer_pending() to check for expiry instead of explicitly checking
against the deadline.
> + } else { \
> + s_->timer = aio_timer_new(qemu_get_aio_context(), \
> + QEMU_CLOCK_REALTIME, SCALE_MS, aio_wait_timer_retry, s_); \
> + aio_wait_timer_retry(s_); \
> + while ((cond)) { \
> + assert(qemu_get_current_aio_context() == \
> + qemu_get_aio_context()); \
> + aio_poll(qemu_get_aio_context(), true); \
> + if (qemu_clock_get_ms(QEMU_CLOCK_REALTIME) > deadline_) { \
> + ret_ = -ETIMEDOUT; \
> + break; \
> + } \
> + } \
> + } \
> + qatomic_dec(&wait_->num_waiters); \
> + timer_free(s_->timer); \
This will need to be timer_del() when the QEMUTimer is moved onto the
stack.
> + g_free(s_); \
> + ret_; })
> +
> #define AIO_WAIT_WHILE(ctx, cond) \
> AIO_WAIT_WHILE_INTERNAL(ctx, cond)
>
> @@ -149,4 +205,6 @@ static inline bool in_aio_context_home_thread(AioContext
> *ctx)
> }
> }
>
> +void aio_wait_timer_retry(void *opaque);
> +
> #endif /* QEMU_AIO_WAIT_H */
> diff --git a/include/block/block-io.h b/include/block/block-io.h
> index b49e0537dd..84f92d2b09 100644
> --- a/include/block/block-io.h
> +++ b/include/block/block-io.h
> @@ -354,6 +354,11 @@ bdrv_co_copy_range(BdrvChild *src, int64_t src_offset,
> AIO_WAIT_WHILE(bdrv_get_aio_context(bs_), \
> cond); })
>
> +#define BDRV_POLL_WHILE_TIMEOUT(bs, cond, timeout) ({ \
> + BlockDriverState *bs_ = (bs); \
> + AIO_WAIT_WHILE_TIMEOUT(bdrv_get_aio_context(bs_), \
> + cond, timeout); })
> +
> void bdrv_drain(BlockDriverState *bs);
>
> int co_wrapper_mixed_bdrv_rdlock
> @@ -431,6 +436,8 @@ bdrv_drain_poll(BlockDriverState *bs, BdrvChild
> *ignore_parent,
> */
> void bdrv_drained_begin(BlockDriverState *bs);
>
> +int bdrv_drained_begin_timeout(BlockDriverState *bs, int64_t timeout_ms);
> +
> /**
> * bdrv_do_drained_begin_quiesce:
> *
> diff --git a/util/aio-wait.c b/util/aio-wait.c
> index b5336cf5fd..9aed165529 100644
> --- a/util/aio-wait.c
> +++ b/util/aio-wait.c
> @@ -84,3 +84,10 @@ void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb,
> void *opaque)
> aio_bh_schedule_oneshot(ctx, aio_wait_bh, &data);
> AIO_WAIT_WHILE_UNLOCKED(NULL, !data.done);
> }
> +
> +void aio_wait_timer_retry(void *opaque)
> +{
> + AioWaitTimer *s = opaque;
> +
> + timer_mod(s->timer, qemu_clock_get_ms(QEMU_CLOCK_REALTIME) +
> s->interval);
> +}
> --
> 2.33.0
>
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