io-wq: allow grabbing existing io-wq

mainline inclusion
from mainline-5.6-rc1
commit eba6f5a3
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

Export a helper to attach to an existing io-wq, rather than setting up
a new one. This is doable now that we have reference counted io_wq's.
Reported-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

fs/io-wq.c

@@ -1115,6 +1115,14 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 	return ERR_PTR(ret);
 }
 
+bool io_wq_get(struct io_wq *wq, struct io_wq_data *data)
+{
+	if (data->get_work != wq->get_work || data->put_work != wq->put_work)
+		return false;
+
+	return refcount_inc_not_zero(&wq->use_refs);
+}
+
 static bool io_wq_worker_wake(struct io_worker *worker, void *data)
 {
 	wake_up_process(worker->task);

fs/io-wq.h

@@ -99,6 +99,7 @@ struct io_wq_data {
 };
 
 struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data);
+bool io_wq_get(struct io_wq *wq, struct io_wq_data *data);
 void io_wq_destroy(struct io_wq *wq);
 
 void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work);