io_uring: refactor io_submit_flush_completions

Don't init req_batch before we actually need it. Also, add a small clean
up for req declaration.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ad85512e12bd3a20d521e9782750300970e5afc8.1624739600.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

fs/io_uring.c

@@ -2132,22 +2132,22 @@ static void io_submit_flush_completions(struct io_ring_ctx *ctx)
 {
 	struct io_comp_state *cs = &ctx->submit_state.comp;
 	int i, nr = cs->nr;
-	struct io_kiocb *req;
 	struct req_batch rb;
 
-	io_init_req_batch(&rb);
 	spin_lock_irq(&ctx->completion_lock);
 	for (i = 0; i < nr; i++) {
-		req = cs->reqs[i];
+		struct io_kiocb *req = cs->reqs[i];
+
 		__io_cqring_fill_event(ctx, req->user_data, req->result,
 					req->compl.cflags);
 	}
 	io_commit_cqring(ctx);
 	spin_unlock_irq(&ctx->completion_lock);
-
 	io_cqring_ev_posted(ctx);
+
+	io_init_req_batch(&rb);
 	for (i = 0; i < nr; i++) {
-		req = cs->reqs[i];
+		struct io_kiocb *req = cs->reqs[i];
 
 		/* submission and completion refs */
 		if (req_ref_sub_and_test(req, 2))