[Devel] [PATCH RH8] aio: ioctl(VE_AIO_IOC_WAIT_ACTIVE) in-flight reqs counting fix

[Pavel Tikhomirov]

Probably s/reqs_avail_batch/reqs_avail/ for better readability as in 
this context batch-es are used to migrate from per-cpu counter to global 
counter, but you don't change counters here.

On 4/23/21 1:57 PM, Alexander Mikhalitsyn wrote:
> We have to take into account percpu part of reqs_available
> counter on struct kioctx.
> 
> Fixes: f5d1279 ("ve/aio: Add a handle to checkpoint/restore AIO context")
> 
> https://jira.sw.ru/browse/PSBM-128710
> 

Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>

> Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
> ---
>   fs/aio.c | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/aio.c b/fs/aio.c
> index 7c547247b056..4ae0cac0f3ff 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1898,9 +1898,19 @@ static bool has_reqs_active(struct kioctx *ctx)
>   {
>   	unsigned long flags;
>   	unsigned nr;
> +	int cpu;
> +	unsigned reqs_avail_batch = 0;
>   
>   	spin_lock_irqsave(&ctx->completion_lock, flags);
> -	nr = (ctx->nr_events - 1) - atomic_read(&ctx->reqs_available);
> +	/*
> +	 * See get_reqs_available()/put_reqs_available() about
> +	 * how reqs_available distributed between atomic
> +	 * ctx->reqs_available and percpu ctx->cpu reqs_available.
> +	 */
> +	for_each_possible_cpu(cpu)
> +		reqs_avail_batch += per_cpu_ptr(ctx->cpu, cpu)->reqs_available;
> +	nr = ctx->nr_events - 1;
> +	nr -= atomic_read(&ctx->reqs_available) + reqs_avail_batch;
>   	nr -= ctx->completed_events;
>   	spin_unlock_irqrestore(&ctx->completion_lock, flags);
>   
> 

-- 
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.