io_uring: kill dead code in io_req_complete_post

Since commit 8f6c829491fe ("io_uring: remove struct io_tw_state::locked"),
io_req_complete_post() is only called from io-wq submit work, where the
request reference is guaranteed to be grabbed and won't drop to zero
in io_req_complete_post().

Kill the dead code, meantime add req_ref_put() to put the reference.

Cc: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1d8297e2046553153e763a52574f0e0f4d512f86.1712331455.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -928,7 +928,6 @@ bool io_req_post_cqe(struct io_kiocb *req, s32 res, u32 cflags)
 static void io_req_complete_post(struct io_kiocb *req, unsigned issue_flags)
 {
 	struct io_ring_ctx *ctx = req->ctx;
-	struct io_rsrc_node *rsrc_node = NULL;
 
 	/*
 	 * Handle special CQ sync cases via task_work. DEFER_TASKRUN requires
@@ -945,42 +944,10 @@ static void io_req_complete_post(struct io_kiocb *req, unsigned issue_flags)
 		if (!io_fill_cqe_req(ctx, req))
 			io_req_cqe_overflow(req);
 	}
-
-	/*
-	 * If we're the last reference to this request, add to our locked
-	 * free_list cache.
-	 */
-	if (req_ref_put_and_test(req)) {
-		if (req->flags & IO_REQ_LINK_FLAGS) {
-			if (req->flags & IO_DISARM_MASK)
-				io_disarm_next(req);
-			if (req->link) {
-				io_req_task_queue(req->link);
-				req->link = NULL;
-			}
-		}
-		io_put_kbuf_comp(req);
-		if (unlikely(req->flags & IO_REQ_CLEAN_FLAGS))
-			io_clean_op(req);
-		io_put_file(req);
-
-		rsrc_node = req->rsrc_node;
-		/*
-		 * Selected buffer deallocation in io_clean_op() assumes that
-		 * we don't hold ->completion_lock. Clean them here to avoid
-		 * deadlocks.
-		 */
-		io_put_task_remote(req->task);
-		wq_list_add_head(&req->comp_list, &ctx->locked_free_list);
-		ctx->locked_free_nr++;
-	}
 	io_cq_unlock_post(ctx);
 
-	if (rsrc_node) {
-		io_ring_submit_lock(ctx, issue_flags);
-		io_put_rsrc_node(ctx, rsrc_node);
-		io_ring_submit_unlock(ctx, issue_flags);
-	}
+	/* called from io-wq submit work only, the ref won't drop to zero */
+	req_ref_put(req);
 }
 
 void io_req_defer_failed(struct io_kiocb *req, s32 res)

io_uring/refs.h

@@ -33,6 +33,13 @@ static inline void req_ref_get(struct io_kiocb *req)
 	atomic_inc(&req->refs);
 }
 
+static inline void req_ref_put(struct io_kiocb *req)
+{
+	WARN_ON_ONCE(!(req->flags & REQ_F_REFCOUNT));
+	WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req));
+	atomic_dec(&req->refs);
+}
+
 static inline void __io_req_set_refcount(struct io_kiocb *req, int nr)
 {
 	if (!(req->flags & REQ_F_REFCOUNT)) {