On Fri, Mar 21, 2025 at 03:09:16PM +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 | 58 +++++++++++++++++++++++++++++++++-------
> include/block/aio-wait.h | 49 +++++++++++++++++++++++++++++++++
> include/block/block-io.h | 22 ++++++++++++++-
> util/aio-wait.c | 5 ++++
> 4 files changed, 123 insertions(+), 11 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index 1ba8d1aeea..912b76c4a4 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -255,6 +255,8 @@ typedef struct {
> bool begin;
> bool poll;
> BdrvChild *parent;
> + uint64_t timeout_ns;
> + int ret;
> } BdrvCoDrainData;
>
> /* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */
> @@ -283,6 +285,10 @@ 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,
> + uint64_t timeout_ns);
> static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
> bool poll);
> static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent);
> @@ -296,7 +302,9 @@ 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_ns);
> } else {
> assert(!data->poll);
> bdrv_do_drained_end(bs, data->parent);
> @@ -310,10 +318,11 @@ 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,
> + uint64_t timeout_ns)
> {
> BdrvCoDrainData data;
> Coroutine *self = qemu_coroutine_self();
> @@ -329,6 +338,8 @@ static void coroutine_fn
> bdrv_co_yield_to_drain(BlockDriverState *bs,
> .begin = begin,
> .parent = parent,
> .poll = poll,
> + .timeout_ns = timeout_ns,
> + .ret = 0
> };
>
> if (bs) {
> @@ -342,16 +353,27 @@ 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, 0);
> +}
> +
> +static int bdrv_do_drained_begin_timeout(BlockDriverState *bs,
> + BdrvChild *parent,
> + bool poll,
> + uint64_t timeout_ns)
> {
> 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_ns);
> }
>
> GLOBAL_STATE_CODE();
> @@ -375,8 +397,17 @@ static void bdrv_do_drained_begin(BlockDriverState *bs,
> BdrvChild *parent,
> * nodes.
> */
> if (poll) {
> - BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
> + return BDRV_POLL_WHILE_TIMEOUT(bs,
> + bdrv_drain_poll_top_level(bs, parent),
> + timeout_ns);
> }
> + return 0;
> +}
> +
> +static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
> + bool poll)
> +{
> + bdrv_do_drained_begin_timeout(bs, parent, poll, 0);
> }
>
> void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, BdrvChild *parent)
> @@ -391,6 +422,13 @@ bdrv_drained_begin(BlockDriverState *bs)
> bdrv_do_drained_begin(bs, NULL, true);
> }
>
> +int coroutine_mixed_fn
> +bdrv_drained_begin_timeout(BlockDriverState *bs, uint64_t timeout_ns)
> +{
> + IO_OR_GS_CODE();
> + return bdrv_do_drained_begin_timeout(bs, NULL, true, timeout_ns);
> +}
> +
> /**
> * This function does not poll, nor must any of its recursively called
> * functions.
> diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
> index cf5e8bde1c..24c31df620 100644
> --- a/include/block/aio-wait.h
> +++ b/include/block/aio-wait.h
> @@ -99,6 +99,53 @@ 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.
> + * @timeout_ns: maximum duration to wait, in nanoseconds, except the value
> + * is unsigned, 0 means infinite.
> + */
> +#define AIO_WAIT_WHILE_TIMEOUT(ctx, cond, timeout_ns) ({ \
> + int ret_ = 0; \
> + uint64_t timeout_ = (timeout_ns); \
> + AioWait *wait_ = &global_aio_wait; \
> + AioContext *ctx_ = (ctx); \
> + AioContext *current_ctx_ = NULL; \
> + QEMUTimer timer_; \
> + /* 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_)) { \
> + current_ctx_ = ctx_; \
> + } else { \
> + assert(qemu_get_current_aio_context() == \
> + qemu_get_aio_context()); \
> + current_ctx_ = qemu_get_aio_context(); \
> + } \
> + if (timeout_ > 0) { \
> + timer_init_full(&timer_, ¤t_ctx_->tlg, \
> + QEMU_CLOCK_REALTIME, \
> + SCALE_NS, 0, aio_wait_timer_cb, NULL); \
> + timer_mod_ns(&timer_, \
> + qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + \
> + timeout_); \
> + } \
> + while ((cond)) { \
> + aio_poll(current_ctx_, true); \
> + if (timeout_ > 0 && !timer_pending(&timer_)) { \
> + ret_ = -ETIMEDOUT; \
> + break; \
> + } \
> + } \
> + if (timeout_ > 0) { \
> + timer_del(&timer_); \
> + } \
> + qatomic_dec(&wait_->num_waiters); \
> + ret_; })
> +
> #define AIO_WAIT_WHILE(ctx, cond) \
> AIO_WAIT_WHILE_INTERNAL(ctx, cond)
It would be nice to unify AIO_WAIT_WHILE_INTERNAL() and
AIO_WAIT_WHILE_TIMEOUT(). I don't see any caller that uses the waited_
return value from AIO_WAIT_WHILE_INTERNAL(), so I think it's possible to
replace AIO_WAIT_WHILE_INTERNAL() with AIO_WAIT_WHILE_TIMEOUT(.., ..., 0).
>
> @@ -149,4 +196,6 @@ static inline bool in_aio_context_home_thread(AioContext
> *ctx)
> }
> }
>
> +void aio_wait_timer_cb(void *opaque);
> +
> #endif /* QEMU_AIO_WAIT_H */
> diff --git a/include/block/block-io.h b/include/block/block-io.h
> index b49e0537dd..844e9cf350 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_ns) ({ \
> + BlockDriverState *bs_ = (bs); \
> + AIO_WAIT_WHILE_TIMEOUT(bdrv_get_aio_context(bs_), \
> + cond, timeout_ns); })
> +
> void bdrv_drain(BlockDriverState *bs);
>
> int co_wrapper_mixed_bdrv_rdlock
> @@ -432,7 +437,22 @@ bdrv_drain_poll(BlockDriverState *bs, BdrvChild
> *ignore_parent,
> void bdrv_drained_begin(BlockDriverState *bs);
>
> /**
> - * bdrv_do_drained_begin_quiesce:
> + * bdrv_drained_begin_timeout:
> + *
> + * Added timeout parameter for bdrv_drained_begin() to make a time limited.
> + *
> + * @timeout_ns: maximum duration to wait; 0 means infinite, equal to call
> + * bdrv_drained_begin().
> + *
> + * Returns: 0 if succeeded; -ETIMEDOUT when a timeout occurs.
> + *
> + * Note: when the timeout fails, we've already begin aquiesced section, so we
> + * still need to call bdrv_drained_end() to end the quiescent section.
> + */
> +int bdrv_drained_begin_timeout(BlockDriverState *bs, uint64_t timeout_ns);
> +
> +/**
> + * bdrv_do_drained_badegin_quiesce:
> *
> * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already
> * running requests to complete.
> diff --git a/util/aio-wait.c b/util/aio-wait.c
> index b5336cf5fd..64c3714fb8 100644
> --- a/util/aio-wait.c
> +++ b/util/aio-wait.c
> @@ -84,3 +84,8 @@ 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_cb(void *opaque)
> +{
> + /* The point is to make AIO_WAIT_WHILE_TIMEOUT()'s aio_poll() return */
> +}
> --
> 2.33.0
>
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