linux-kernel - [PATCH 1/2] io-wq: allow grabbing existing io-wq

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Message-Id: <404c434402d7a41a80f1e4f6bb7dc3ef9123f493.1580169415.git.asml.silence@gmail.com>
Date:   Tue, 28 Jan 2020 03:06:51 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] io-wq: allow grabbing existing io-wq

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

Reported-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io-wq.c | 10 ++++++++++
 fs/io-wq.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index b45d585cdcc8..36d05503b982 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -1110,6 +1110,16 @@ 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->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);
+}
+
 static bool io_wq_worker_wake(struct io_worker *worker, void *data)
 {
 	wake_up_process(worker->task);
diff --git a/fs/io-wq.h b/fs/io-wq.h
index 167316ad447e..c42602c58c56 100644
--- a/fs/io-wq.h
+++ b/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);
-- 
2.24.0