linux-kernel - Re: [PATCH v5 3/6] vhost: Add the cgroup related function

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Message-ID: <CACGkMEu29fZxNoyLOytScwFqFSFP+o3-ETSgG8u4Kgq_yEt6Gw@mail.gmail.com>
Date: Thu, 2 Jan 2025 11:29:06 +0800
From: Jason Wang <jasowang@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: mst@...hat.com, michael.christie@...cle.com, sgarzare@...hat.com, 
	linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v5 3/6] vhost: Add the cgroup related function

On Mon, Dec 30, 2024 at 8:45 PM Cindy Lu <lulu@...hat.com> wrote:
>
> Reintroduce the previously removed functions vhost_attach_cgroups_work()
> and vhost_attach_cgroups() to support kthread mode. Rename
> vhost_attach_cgroups() to vhost_attach_task_to_cgroups(), and include
> the implementation of the old function vhost_dev_flush() in this
> new function.
>
> These function was removed in
> commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
>
> Signed-off-by: Cindy Lu <lulu@...hat.com>
> ---
>  drivers/vhost/vhost.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 1feba29abf95..812dfd218bc2 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 +621,38 @@ 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_flush_struct flush;
> +       struct vhost_attach_cgroups_struct attach;
> +
> +       attach.owner = current;
> +
> +       vhost_work_init(&attach.work, vhost_attach_cgroups_work);
> +       vhost_worker_queue(worker, &attach.work);
> +
> +       init_completion(&flush.wait_event);
> +       vhost_work_init(&flush.work, vhost_flush_work);
> +       vhost_worker_queue(worker, &flush.work);
> +       wait_for_completion(&flush.wait_event);
> +
> +       return attach.ret;
> +}

This seems to be inconsistent with what you said above which is

"""
> These function was removed in
> commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
"""

As 6e890c5d5021 had:

static int vhost_attach_cgroups(struct vhost_dev *dev)
{
        struct vhost_attach_cgroups_struct attach;

        attach.owner = current;
        vhost_work_init(&attach.work, vhost_attach_cgroups_work);
        vhost_work_queue(dev, &attach.work);
        vhost_dev_flush(dev);
        return attach.ret;
}

It seems current vhost_dev_flush() will still work or the open coding
of the flush logic needs to be explained.

Thanks

> +
>  /* Caller should have device mutex */
>  bool vhost_dev_has_owner(struct vhost_dev *dev)
>  {
> --
> 2.45.0
>