On Wed, Sep 15, 2021 at 11:46 AM Jens Axboe [off-list ref] wrote:

   The usual tests
do end up hitting the -EAGAIN path quite easily for certain device
types, but not the short read/write.

No way to do something like "read in file to make sure it's cached,
then invalidate caches from position X with POSIX_FADV_DONTNEED, then
do a read that crosses that cached/uncached boundary"?

To at least verify that "partly synchronous, but partly punted to async" case?

Or were you talking about some other situation?

            Linus