[PATCH 3/4] io-wq: allow lookup of existing io_wq with given id

[Jens Axboe <axboe@kernel.dk>]

If the id and user/creds match, return an existing io_wq if we can safely
grab a reference to it.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io-wq.c | 37 ++++++++++++++++++++++++++++++++++++-
 fs/io-wq.h | 11 ++++++++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 51b3677d6fbd..08ef69b498f6 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -1024,7 +1024,7 @@ void io_wq_flush(struct io_wq *wq)
 	}
 }
 
-struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
+static struct io_wq *__io_wq_create(unsigned bounded, struct io_wq_data *data)
 {
 	int ret = -ENOMEM, node;
 	struct io_wq *wq;
@@ -1106,6 +1106,36 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 	return ERR_PTR(ret);
 }
 
+static bool io_wq_match(struct io_wq *wq, struct io_wq_data *data)
+{
+	if (data->creds != wq->creds || data->user != wq->user)
+		return false;
+	if (data->get_work != wq->get_work || data->put_work != wq->put_work)
+		return false;
+	return refcount_inc_not_zero(&wq->use_refs);
+}
+
+/*
+ * Find and return io_wq with given id and grab a reference to it.
+ */
+struct io_wq *io_wq_create_id(unsigned bounded, struct io_wq_data *data,
+			      unsigned int id)
+{
+	if (id) {
+		struct io_wq *wq;
+
+		mutex_lock(&wq_lock);
+		wq = idr_find(&wq_idr, id);
+		if (wq && io_wq_match(wq, data)) {
+			mutex_unlock(&wq_lock);
+			return wq;
+		}
+		mutex_unlock(&wq_lock);
+	}
+
+	return __io_wq_create(bounded, data);
+}
+
 static bool io_wq_worker_wake(struct io_worker *worker, void *data)
 {
 	wake_up_process(worker->task);
@@ -1145,3 +1175,8 @@ void io_wq_destroy(struct io_wq *wq)
 		__io_wq_destroy(wq);
 	}
 }
+
+unsigned int io_wq_id(struct io_wq *wq)
+{
+	return wq->id;
+}
diff --git a/fs/io-wq.h b/fs/io-wq.h
index 1cd039af8813..dee7bb3b7cd4 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -97,8 +97,17 @@ struct io_wq_data {
 	put_work_fn *put_work;
 };
 
-struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data);
+struct io_wq *io_wq_create_id(unsigned bounded, struct io_wq_data *data,
+				unsigned int id);
+
+static inline struct io_wq *io_wq_create(unsigned bounded,
+					 struct io_wq_data *data)
+{
+	return io_wq_create_id(bounded, data, 0);
+}
+
 void io_wq_destroy(struct io_wq *wq);
+unsigned int io_wq_id(struct io_wq *wq);
 
 void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work);
 void io_wq_enqueue_hashed(struct io_wq *wq, struct io_wq_work *work, void *val);
-- 
2.25.0