Pull core block fix from Jens Axboe:
"Jan reported a problem this morning with a crash in blk-mq, and after
looking over the recent changes, it's obvious that the blk-mq-tag
waitqueue handling change is buggy. We could end up _not_ doing
finish_wait() before switching to a new waitqueue, thus corrupting the
wait task list"
* 'for-linus' of git://git.kernel.dk/linux-block:
Revert "blk-mq: Micro-optimize bt_get()"