[v8] vhost: Add support of kthread API

[PATCH v8 3/8] vhost: Add the cgroup related function

Posted by Cindy Lu 8 months, 3 weeks ago

Add back the previously removed cgroup function to support the kthread
The biggest change for this part is in vhost_attach_cgroups() and
vhost_attach_task_to_cgroups().

The old function was remove in
commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 drivers/vhost/vhost.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9500e85b42ce..20571bd6f7bd 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -22,6 +22,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/kthread.h>
+#include <linux/cgroup.h>
 #include <linux/module.h>
 #include <linux/sort.h>
 #include <linux/sched/mm.h>
@@ -620,6 +621,46 @@ long vhost_dev_check_owner(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
 
+struct vhost_attach_cgroups_struct {
+	struct vhost_work work;
+	struct task_struct *owner;
+	int ret;
+};
+
+static void vhost_attach_cgroups_work(struct vhost_work *work)
+{
+	struct vhost_attach_cgroups_struct *s;
+
+	s = container_of(work, struct vhost_attach_cgroups_struct, work);
+	s->ret = cgroup_attach_task_all(s->owner, current);
+}
+
+static int vhost_attach_task_to_cgroups(struct vhost_worker *worker)
+{
+	struct vhost_attach_cgroups_struct attach;
+	int saved_cnt;
+
+	attach.owner = current;
+
+	vhost_work_init(&attach.work, vhost_attach_cgroups_work);
+	vhost_worker_queue(worker, &attach.work);
+
+	mutex_lock(&worker->mutex);
+
+	/*
+	 * Bypass attachment_cnt check in __vhost_worker_flush:
+	 * Temporarily change it to INT_MAX to bypass the check
+	 */
+	saved_cnt = worker->attachment_cnt;
+	worker->attachment_cnt = INT_MAX;
+	__vhost_worker_flush(worker);
+	worker->attachment_cnt = saved_cnt;
+
+	mutex_unlock(&worker->mutex);
+
+	return attach.ret;
+}
+
 /* Caller should have device mutex */
 bool vhost_dev_has_owner(struct vhost_dev *dev)
 {
-- 
2.45.0

Re: [PATCH v8 3/8] vhost: Add the cgroup related function

Posted by Markus Elfring 8 months, 2 weeks ago

…
> +++ b/drivers/vhost/vhost.c
…
> +static int vhost_attach_task_to_cgroups(struct vhost_worker *worker)
> +{
…
> +	vhost_worker_queue(worker, &attach.work);
> +
> +	mutex_lock(&worker->mutex);
…
> +	mutex_unlock(&worker->mutex);
> +
> +	return attach.ret;
> +}
…

Under which circumstances would you become interested to apply a statement
like “guard(mutex)(&worker->mutex);”?
https://elixir.bootlin.com/linux/v6.14-rc6/source/include/linux/mutex.h#L201

Regards,
Markus

Re: [PATCH v8 3/8] vhost: Add the cgroup related function

Posted by Stefano Garzarella 8 months, 3 weeks ago

On Fri, Mar 28, 2025 at 06:02:47PM +0800, Cindy Lu wrote:
>Add back the previously removed cgroup function to support the kthread

nit: Missing . at the end

>The biggest change for this part is in vhost_attach_cgroups() and
>vhost_attach_task_to_cgroups().
>
>The old function was remove in

nit: s/remove/removed

>commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
>
>Signed-off-by: Cindy Lu <lulu@redhat.com>
>---
> drivers/vhost/vhost.c | 41 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 41 insertions(+)

As I mentioned, this patch also has unused functions, but LGTM.

Thanks,
Stefano

>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index 9500e85b42ce..20571bd6f7bd 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -22,6 +22,7 @@
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> #include <linux/kthread.h>
>+#include <linux/cgroup.h>
> #include <linux/module.h>
> #include <linux/sort.h>
> #include <linux/sched/mm.h>
>@@ -620,6 +621,46 @@ long vhost_dev_check_owner(struct vhost_dev *dev)
> }
> EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
>
>+struct vhost_attach_cgroups_struct {
>+	struct vhost_work work;
>+	struct task_struct *owner;
>+	int ret;
>+};
>+
>+static void vhost_attach_cgroups_work(struct vhost_work *work)
>+{
>+	struct vhost_attach_cgroups_struct *s;
>+
>+	s = container_of(work, struct vhost_attach_cgroups_struct, work);
>+	s->ret = cgroup_attach_task_all(s->owner, current);
>+}
>+
>+static int vhost_attach_task_to_cgroups(struct vhost_worker *worker)
>+{
>+	struct vhost_attach_cgroups_struct attach;
>+	int saved_cnt;
>+
>+	attach.owner = current;
>+
>+	vhost_work_init(&attach.work, vhost_attach_cgroups_work);
>+	vhost_worker_queue(worker, &attach.work);
>+
>+	mutex_lock(&worker->mutex);
>+
>+	/*
>+	 * Bypass attachment_cnt check in __vhost_worker_flush:
>+	 * Temporarily change it to INT_MAX to bypass the check
>+	 */
>+	saved_cnt = worker->attachment_cnt;
>+	worker->attachment_cnt = INT_MAX;
>+	__vhost_worker_flush(worker);
>+	worker->attachment_cnt = saved_cnt;
>+
>+	mutex_unlock(&worker->mutex);
>+
>+	return attach.ret;
>+}
>+
> /* Caller should have device mutex */
> bool vhost_dev_has_owner(struct vhost_dev *dev)
> {
>-- 
>2.45.0
>