io-wq: fix bug of creating io-wokers unconditionally

The former patch to add check between nr_workers and max_workers has a
bug, which will cause unconditionally creating io-workers. That's
because the result of the check doesn't affect the call of
create_io_worker(), fix it by bringing in a boolean value for it.

Fixes: 2169827 ("io-wq: fix lack of acct->nr_workers < acct->max_workers judgement")
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20210808135434.68667-2-haoxu@linux.alibaba.com
[axboe: drop hunk that isn't strictly needed]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Hao Xu

fs/io-wq.c

@@ -282,16 +282,24 @@ static void create_worker_cb(struct callback_head *cb)
 	struct io_wq *wq;
 	struct io_wqe *wqe;
 	struct io_wqe_acct *acct;
+	bool do_create = false;
 
 	cwd = container_of(cb, struct create_worker_data, work);
 	wqe = cwd->wqe;
 	wq = wqe->wq;
 	acct = &wqe->acct[cwd->index];
 	raw_spin_lock_irq(&wqe->lock);
-	if (acct->nr_workers < acct->max_workers)
+	if (acct->nr_workers < acct->max_workers) {
 		acct->nr_workers++;
+		do_create = true;
+	}
 	raw_spin_unlock_irq(&wqe->lock);
-	create_io_worker(wq, cwd->wqe, cwd->index);
+	if (do_create) {
+		create_io_worker(wq, cwd->wqe, cwd->index);
+	} else {
+		atomic_dec(&acct->nr_running);
+		io_worker_ref_put(wq);
+	}
 	kfree(cwd);
 }