io_uring: use original request task for inflight tracking

In prior kernels, we did file assignment always at prep time. This meant
that req->task == current. But after deferring that assignment and then
pushing the inflight tracking back in, we've got the inflight tracking
using current when it should in fact now be using req->task.

Fixup that error introduced by adding the inflight tracking back after
file assignments got modifed.

Fixes: 9cae36a0 ("io_uring: reinstate the inflight tracking")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1975,7 +1975,7 @@ static inline void io_req_track_inflight(struct io_kiocb *req)
 {
 	if (!(req->flags & REQ_F_INFLIGHT)) {
 		req->flags |= REQ_F_INFLIGHT;
-		atomic_inc(&current->io_uring->inflight_tracked);
+		atomic_inc(&req->task->io_uring->inflight_tracked);
 	}
 }