Commit 099ada2c authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring/rw: add write support for IOCB_DIO_CALLER_COMP 



If the filesystem dio handler understands IOCB_DIO_CALLER_COMP, we'll
get a kiocb->ki_complete() callback with kiocb->dio_complete set. In
that case, rather than complete the IO directly through task_work, queue
up an intermediate task_work handler that first processes this callback
and then immediately completes the request.

For XFS, this avoids a punt through a workqueue, which is a lot less
efficient and adds latency to lower queue depth (or sync) O_DIRECT
writes.

Only do this for non-polled IO, as polled IO doesn't need this kind
of deferral as it always completes within the task itself. This then
avoids a check for deferral in the polled IO completion handler.

Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9cf3516c

io_uring/rw.c

+24 −3
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
	} else {

		rw->kiocb.ki_ioprio = get_current_ioprio();

	}

	rw->kiocb.dio_complete = NULL;



	rw->addr = READ_ONCE(sqe->addr);

	rw->len = READ_ONCE(sqe->len);
@@ -285,6 +286,15 @@ static inline int io_fixup_rw_res(struct io_kiocb *req, long res) 


void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts)

{

	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);

	struct kiocb *kiocb = &rw->kiocb;



	if ((kiocb->ki_flags & IOCB_DIO_CALLER_COMP) && kiocb->dio_complete) {

		long res = kiocb->dio_complete(rw->kiocb.private);



		io_req_set_res(req, io_fixup_rw_res(req, res), 0);

	}



	io_req_io_end(req);



	if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) {
@@ -300,9 +310,11 @@ static void io_complete_rw(struct kiocb *kiocb, long res) 
	struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);

	struct io_kiocb *req = cmd_to_io_kiocb(rw);



	if (!kiocb->dio_complete || !(kiocb->ki_flags & IOCB_DIO_CALLER_COMP)) {

		if (__io_complete_rw_common(req, res))

			return;

		io_req_set_res(req, io_fixup_rw_res(req, res), 0);

	}

	req->io_task_work.func = io_req_rw_complete;

	__io_req_task_work_add(req, IOU_F_TWQ_LAZY_WAKE);

}
@@ -916,6 +928,15 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags) 
	}

	kiocb->ki_flags |= IOCB_WRITE;



	/*

	 * For non-polled IO, set IOCB_DIO_CALLER_COMP, stating that our handler

	 * groks deferring the completion to task context. This isn't

	 * necessary and useful for polled IO as that can always complete

	 * directly.

	 */

	if (!(kiocb->ki_flags & IOCB_HIPRI))

		kiocb->ki_flags |= IOCB_DIO_CALLER_COMP;



	if (likely(req->file->f_op->write_iter))

		ret2 = call_write_iter(req->file, kiocb, &s->iter);

	else if (req->file->f_op->write)