linux-kernel - [PATCH v6 5/8] selftests: ublk: kublk: lift queue initialization out of thread

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Message-Id: <20250507-ublk_task_per_io-v6-5-a2a298783c01@purestorage.com>
Date: Wed, 07 May 2025 15:49:39 -0600
From: Uday Shankar <ushankar@...estorage.com>
To: Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>, 
 Caleb Sander Mateos <csander@...estorage.com>, 
 Andrew Morton <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>, 
 Jonathan Corbet <corbet@....net>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org, 
 Uday Shankar <ushankar@...estorage.com>
Subject: [PATCH v6 5/8] selftests: ublk: kublk: lift queue initialization
 out of thread

Currently, each ublk server I/O handler thread initializes its own
queue. However, as we move towards decoupled ublk_queues and ublk server
threads, this model does not make sense anymore, as there will no longer
be a concept of a thread having "its own" queue. So lift queue
initialization out of the per-thread ublk_io_handler_fn and into a loop
in ublk_start_daemon (which runs once for each device).

There is a part of ublk_queue_init (ring initialization) which does
actually need to happen on the thread that will use the ring; that is
separated into a separate ublk_thread_init which is still called by each
I/O handler thread.

Signed-off-by: Uday Shankar <ushankar@...estorage.com>
---
 tools/testing/selftests/ublk/kublk.c | 58 ++++++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/ublk/kublk.c b/tools/testing/selftests/ublk/kublk.c
index 7b3af98546803134dd7f959c40408cefda7cd45c..3ad9e162816c3a10e9928f9d530908cda7595530 100644
--- a/tools/testing/selftests/ublk/kublk.c
+++ b/tools/testing/selftests/ublk/kublk.c
@@ -388,6 +388,17 @@ static void ublk_queue_deinit(struct ublk_queue *q)
 	int i;
 	int nr_ios = q->q_depth;
 
+	if (q->io_cmd_buf)
+		munmap(q->io_cmd_buf, ublk_queue_cmd_buf_sz(q));
+
+	for (i = 0; i < nr_ios; i++)
+		free(q->ios[i].buf_addr);
+}
+
+static void ublk_thread_deinit(struct ublk_queue *q)
+{
+	q->tid = 0;
+
 	io_uring_unregister_buffers(&q->ring);
 
 	io_uring_unregister_ring_fd(&q->ring);
@@ -397,28 +408,20 @@ static void ublk_queue_deinit(struct ublk_queue *q)
 		close(q->ring.ring_fd);
 		q->ring.ring_fd = -1;
 	}
-
-	if (q->io_cmd_buf)
-		munmap(q->io_cmd_buf, ublk_queue_cmd_buf_sz(q));
-
-	for (i = 0; i < nr_ios; i++)
-		free(q->ios[i].buf_addr);
 }
 
 static int ublk_queue_init(struct ublk_queue *q)
 {
 	struct ublk_dev *dev = q->dev;
 	int depth = dev->dev_info.queue_depth;
-	int i, ret = -1;
+	int i;
 	int cmd_buf_size, io_buf_size;
 	unsigned long off;
-	int ring_depth = dev->tgt.sq_depth, cq_depth = dev->tgt.cq_depth;
 
 	q->tgt_ops = dev->tgt.ops;
 	q->state = 0;
 	q->q_depth = depth;
 	q->cmd_inflight = 0;
-	q->tid = gettid();
 
 	if (dev->dev_info.flags & UBLK_F_SUPPORT_ZERO_COPY) {
 		q->state |= UBLKSRV_NO_BUF;
@@ -452,6 +455,22 @@ static int ublk_queue_init(struct ublk_queue *q)
 		}
 	}
 
+	return 0;
+ fail:
+	ublk_queue_deinit(q);
+	ublk_err("ublk dev %d queue %d failed\n",
+			dev->dev_info.dev_id, q->q_id);
+	return -ENOMEM;
+}
+
+static int ublk_thread_init(struct ublk_queue *q)
+{
+	struct ublk_dev *dev = q->dev;
+	int ring_depth = dev->tgt.sq_depth, cq_depth = dev->tgt.cq_depth;
+	int ret;
+
+	q->tid = gettid();
+
 	ret = ublk_setup_ring(&q->ring, ring_depth, cq_depth,
 			IORING_SETUP_COOP_TASKRUN |
 			IORING_SETUP_SINGLE_ISSUER |
@@ -481,9 +500,9 @@ static int ublk_queue_init(struct ublk_queue *q)
 	}
 
 	return 0;
- fail:
-	ublk_queue_deinit(q);
-	ublk_err("ublk dev %d queue %d failed\n",
+fail:
+	ublk_thread_deinit(q);
+	ublk_err("ublk dev %d queue %d thread init failed\n",
 			dev->dev_info.dev_id, q->q_id);
 	return -ENOMEM;
 }
@@ -740,9 +759,9 @@ static void *ublk_io_handler_fn(void *data)
 	int dev_id = q->dev->dev_info.dev_id;
 	int ret;
 
-	ret = ublk_queue_init(q);
+	ret = ublk_thread_init(q);
 	if (ret) {
-		ublk_err("ublk dev %d queue %d init queue failed\n",
+		ublk_err("ublk dev %d queue %d thread init failed\n",
 				dev_id, q->q_id);
 		return NULL;
 	}
@@ -761,7 +780,7 @@ static void *ublk_io_handler_fn(void *data)
 	} while (1);
 
 	ublk_dbg(UBLK_DBG_QUEUE, "ublk dev %d queue %d exited\n", dev_id, q->q_id);
-	ublk_queue_deinit(q);
+	ublk_thread_deinit(q);
 	return NULL;
 }
 
@@ -830,6 +849,13 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev)
 		dev->q[i].dev = dev;
 		dev->q[i].q_id = i;
 
+		ret = ublk_queue_init(&dev->q[i]);
+		if (ret) {
+			ublk_err("ublk dev %d queue %d init queue failed\n",
+				 dinfo->dev_id, i);
+			goto fail;
+		}
+
 		qinfo[i].q = &dev->q[i];
 		qinfo[i].queue_sem = &queue_sem;
 		qinfo[i].affinity = &affinity_buf[i];
@@ -865,6 +891,8 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev)
 	for (i = 0; i < dinfo->nr_hw_queues; i++)
 		pthread_join(dev->q[i].thread, &thread_ret);
  fail:
+	for (i = 0; i < dinfo->nr_hw_queues; i++)
+		ublk_queue_deinit(&dev->q[i]);
 	ublk_dev_unprep(dev);
 	ublk_dbg(UBLK_DBG_DEV, "%s exit\n", __func__);
 

-- 
2.34.1