On Tue, Apr 08, 2025 at 08:49:54PM -0600, Caleb Sander Mateos wrote: > The ublk driver calls blk_mq_tag_to_rq() in several places. > blk_mq_tag_to_rq() tolerates an invalid tag for the tagset, checking it > against the number of tags and returning NULL if it is out of bounds. > But all the calls from the ublk driver have already verified the tag > against the ublk queue's queue depth. In ublk_commit_completion(), > ublk_handle_need_get_data(), and case UBLK_IO_COMMIT_AND_FETCH_REQ, the > tag has already been checked in __ublk_ch_uring_cmd(). In > ublk_abort_queue(), the loop bounds the tag by the queue depth. In > __ublk_check_and_get_req(), the tag has already been checked in > __ublk_ch_uring_cmd(), in the case of ublk_register_io_buf(), or in > ublk_check_and_get_req(). > > So just index the tagset's rqs array directly in the ublk driver. > Convert the tags to unsigned, as blk_mq_tag_to_rq() does. Poking directly into block layer internals feels like a really bad idea. If this is important enough we'll need a non-checking helper in the core code, but as with all these kinds of micro-optimizations it better have a really good justification.
