On Sat, Oct 16, 2021 at 07:37:35PM -0600, Jens Axboe wrote:

If we don't use an IO scheduler or have shared tags, then we don't need
to call into this external function at all. This saves ~2% for such
a setup.

This looks correct, although the call chain gets a little confusing
now.  How much difference is this over basically inlining the
whole old blk_mq_get_driver_tag?