[PATCH 10/11] vhost: move worker thread fields to new struct

Mike Christie
2023-03-10T22:06:32Z

This is just a prep patch. It moves the worker related fields to a new
vhost_worker struct and moves the code around to create some helpers that
will be used in the next patch.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
drivers/vhost/vhost.c | 98 ++++++++++++++++++++++++++++---------------
drivers/vhost/vhost.h | 11 +++--
2 files changed, 72 insertions(+), 37 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 43c9770b86e5..60282fe5c338 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -255,8 +255,8 @@ void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
* sure it was not in the list.
* test_and_set_bit() implies a memory barrier.
*/
- llist_add(&work->node, &dev->work_list);
- wake_up_process(dev->worker);
+ llist_add(&work->node, &dev->worker->work_list);
+ wake_up_process(dev->worker->task);
}
}
EXPORT_SYMBOL_GPL(vhost_work_queue);
@@ -264,7 +264,7 @@ EXPORT_SYMBOL_GPL(vhost_work_queue);
/* A lockless hint for busy polling code to exit the loop */
bool vhost_has_work(struct vhost_dev *dev)
{
- return !llist_empty(&dev->work_list);
+ return dev->worker && !llist_empty(&dev->worker->work_list);
}
EXPORT_SYMBOL_GPL(vhost_has_work);

@@ -335,7 +335,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,

static int vhost_worker(void *data)
{
- struct vhost_dev *dev = data;
+ struct vhost_worker *worker = data;
+ struct vhost_dev *dev = worker->dev;
struct vhost_work *work, *work_next;
struct llist_node *node;

@@ -350,7 +351,7 @@ static int vhost_worker(void *data)
break;
}

- node = llist_del_all(&dev->work_list);
+ node = llist_del_all(&worker->work_list);
if (!node)
schedule();

@@ -360,7 +361,7 @@ static int vhost_worker(void *data)
llist_for_each_entry_safe(work, work_next, node, node) {
clear_bit(VHOST_WORK_QUEUED, &work->flags);
__set_current_state(TASK_RUNNING);
- kcov_remote_start_common(dev->kcov_handle);
+ kcov_remote_start_common(worker->kcov_handle);
work->fn(work);
kcov_remote_stop();
if (need_resched())
@@ -479,7 +480,6 @@ void vhost_dev_init(struct vhost_dev *dev,
dev->byte_weight = byte_weight;
dev->use_worker = use_worker;
dev->msg_handler = msg_handler;
- init_llist_head(&dev->work_list);
init_waitqueue_head(&dev->wait);
INIT_LIST_HEAD(&dev->read_list);
INIT_LIST_HEAD(&dev->pending_list);
@@ -571,10 +571,60 @@ static void vhost_detach_mm(struct vhost_dev *dev)
dev->mm = NULL;
}

+static void vhost_worker_free(struct vhost_dev *dev)
+{
+ struct vhost_worker *worker = dev->worker;
+
+ if (!worker)
+ return;
+
+ dev->worker = NULL;
+ WARN_ON(!llist_empty(&worker->work_list));
+ kthread_stop(worker->task);
+ kfree(worker);
+}
+
+static int vhost_worker_create(struct vhost_dev *dev)
+{
+ struct vhost_worker *worker;
+ struct task_struct *task;
+ int ret;
+
+ worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
+ if (!worker)
+ return -ENOMEM;
+
+ dev->worker = worker;
+ worker->dev = dev;
+ worker->kcov_handle = kcov_common_handle();
+ init_llist_head(&worker->work_list);
+
+ task = kthread_create(vhost_worker, worker, "vhost-%d", current->pid);
+ if (IS_ERR(task)) {
+ ret = PTR_ERR(task);
+ goto free_worker;
+ }
+
+ worker->task = task;
+ wake_up_process(task); /* avoid contributing to loadavg */
+
+ ret = vhost_attach_cgroups(dev);
+ if (ret)
+ goto stop_worker;
+
+ return 0;
+
+stop_worker:
+ kthread_stop(worker->task);
+free_worker:
+ kfree(worker);
+ dev->worker = NULL;
+ return ret;
+}
+
/* Caller should have device mutex */
long vhost_dev_set_owner(struct vhost_dev *dev)
{
- struct task_struct *worker;
int err;

/* Is there an owner already? */
@@ -585,36 +635,21 @@ long vhost_dev_set_owner(struct vhost_dev *dev)

vhost_attach_mm(dev);

- dev->kcov_handle = kcov_common_handle();
if (dev->use_worker) {
- worker = kthread_create(vhost_worker, dev,
- "vhost-%d", current->pid);
- if (IS_ERR(worker)) {
- err = PTR_ERR(worker);
- goto err_worker;
- }
-
- dev->worker = worker;
- wake_up_process(worker); /* avoid contributing to loadavg */
-
- err = vhost_attach_cgroups(dev);
+ err = vhost_worker_create(dev);
if (err)
- goto err_cgroup;
+ goto err_worker;
}

err = vhost_dev_alloc_iovecs(dev);
if (err)
- goto err_cgroup;
+ goto err_iovecs;

return 0;
-err_cgroup:
- if (dev->worker) {
- kthread_stop(dev->worker);
- dev->worker = NULL;
- }
+err_iovecs:
+ vhost_worker_free(dev);
err_worker:
vhost_detach_mm(dev);
- dev->kcov_handle = 0;
err_mm:
return err;
}
@@ -705,12 +740,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
dev->iotlb = NULL;
vhost_clear_msg(dev);
wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
- WARN_ON(!llist_empty(&dev->work_list));
- if (dev->worker) {
- kthread_stop(dev->worker);
- dev->worker = NULL;
- dev->kcov_handle = 0;
- }
+ vhost_worker_free(dev);
vhost_detach_mm(dev);
}
EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 790b296271f1..3a98c4f06b5a 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -25,6 +25,13 @@ struct vhost_work {
unsigned long flags;
};

+struct vhost_worker {
+ struct task_struct *task;
+ struct llist_head work_list;
+ struct vhost_dev *dev;
+ u64 kcov_handle;
+};
+
/* Poll a file (eventfd or socket) */
/* Note: there's nothing vhost specific about this structure. */
struct vhost_poll {
@@ -147,8 +154,7 @@ struct vhost_dev {
struct vhost_virtqueue **vqs;
int nvqs;
struct eventfd_ctx *log_ctx;
- struct llist_head work_list;
- struct task_struct *worker;
+ struct vhost_worker *worker;
struct vhost_iotlb *umem;
struct vhost_iotlb *iotlb;
spinlock_t iotlb_lock;
@@ -158,7 +164,6 @@ struct vhost_dev {
int iov_limit;
int weight;
int byte_weight;
- u64 kcov_handle;
bool use_worker;
int (*msg_handler)(struct vhost_dev *dev, u32 asid,
struct vhost_iotlb_msg *msg);
--
2.25.1