[Devel] [PATCH VZ9 02/11] vhost: dynamically allocate vhost_worker

[Andrey Zhadchenko]

From: Mike Christie <michael.christie at oracle.com>

This patchset allows us to allocate multiple workers, so this has us
move from the vhost_worker that's embedded in the vhost_dev to
dynamically allocating it.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
Message-Id: <20230626232307.97930-3-michael.christie at oracle.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>

---------
Half of this commit is already present. Add the rest.

(cherry picked from ms commit c011bb669ddc)
https://virtuozzo.atlassian.net/browse/PSBM-152375
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
 drivers/vhost/vhost.c | 20 ++++++++++++--------
 drivers/vhost/vhost.h |  2 +-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 3421525c8e20..2dd032fbf642 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -235,21 +235,23 @@ void vhost_dev_flush(struct vhost_dev *dev)
 {
 	struct vhost_flush_struct flush;
 
-	if (dev->worker) {
-		init_completion(&flush.wait_event);
-		vhost_work_init(&flush.work, vhost_flush_work);
+	init_completion(&flush.wait_event);
+	vhost_work_init(&flush.work, vhost_flush_work);
 
-		vhost_work_queue(dev, &flush.work);
+	if (vhost_work_queue(dev, &flush.work))
 		wait_for_completion(&flush.wait_event);
-	}
 }
 EXPORT_SYMBOL_GPL(vhost_dev_flush);
 
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
+bool vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 {
 	if (!dev->worker)
-		return;
-
+		return false;
+	/*
+	 * vsock can queue while we do a VHOST_SET_OWNER, so we have a smp_wmb
+	 * when setting up the worker. We don't have a smp_rmb here because
+	 * test_and_set_bit gives us a mb already.
+	 */
 	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
 		/* We can only add the work to the list after we're
 		 * sure it was not in the list.
@@ -258,6 +260,8 @@ void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 		llist_add(&work->node, &dev->worker->work_list);
 		wake_up_process(dev->worker->task);
 	}
+
+	return true;
 }
 EXPORT_SYMBOL_GPL(vhost_work_queue);
 
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 2df99e657ec6..9ff8c0afcead 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -44,7 +44,7 @@ struct vhost_poll {
 };
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
-void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
+bool vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
 bool vhost_has_work(struct vhost_dev *dev);
 
 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
-- 
2.39.3