Re: [PATCH v2] fs/splice: don't block splice_direct_to_actor() after data was read

[Christian Brauner]

> +		/*
> +		 * After at least one byte was read from the input
> +		 * file, don't wait for blocking I/O in the following
> +		 * loop iterations; instead of blocking for arbitrary
> +		 * amounts of time in the kernel, let userspace decide
> +		 * how to proceed.  This avoids excessive latency if
> +		 * the output is being consumed faster than the input
> +		 * file can fill it (e.g. sendfile() from a slow hard
> +		 * disk to a fast network).
> +		 */
> +		flags |= SPLICE_F_NOWAIT;
> +

Hm, so the thing that is worrysome about this change is that this may
cause regressions afaict as this is a pretty significant change from
current behavior.