linux-kernel - Re: [PATCH 1/6] vhost: get rid of vhost_poll

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Message-ID: <20211116143323.g7c27u2ho4vpp4cp@steredhat>
Date:   Tue, 16 Nov 2021 15:33:23 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Andrey Ryabinin <arbn@...dex-team.com>,
        Mike Christie <michael.christie@...cle.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] vhost: get rid of vhost_poll_flush() wrapper

On Mon, Nov 15, 2021 at 06:29:58PM +0300, Andrey Ryabinin wrote:
>vhost_poll_flush() is a simple wrapper around vhost_work_dev_flush().
>It gives wrong impression that we are doing some work over vhost_poll,
>while in fact it flushes vhost_poll->dev.
>It only complicate understanding of the code and leads to mistakes
>like flushing the same vhost_dev several times in a row.
>
>Just remove vhost_poll_flush() and call vhost_work_dev_flush() directly.
>
>Signed-off-by: Andrey Ryabinin <arbn@...dex-team.com>
>---
> drivers/vhost/net.c   |  4 ++--
> drivers/vhost/test.c  |  2 +-
> drivers/vhost/vhost.c | 12 ++----------
> drivers/vhost/vsock.c |  2 +-
> 4 files changed, 6 insertions(+), 14 deletions(-)

Adding Mike since these changes could be relevant for "[PATCH V4 00/12] 
vhost: multiple worker support" [1] series.

>
>diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>index 28ef323882fb..11221f6d11b8 100644
>--- a/drivers/vhost/net.c
>+++ b/drivers/vhost/net.c
>@@ -1375,8 +1375,8 @@ static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
>
> static void vhost_net_flush_vq(struct vhost_net *n, int index)
> {
>-	vhost_poll_flush(n->poll + index);
>-	vhost_poll_flush(&n->vqs[index].vq.poll);
>+	vhost_work_dev_flush(n->poll[index].dev);
>+	vhost_work_dev_flush(n->vqs[index].vq.poll.dev);
> }
>
> static void vhost_net_flush(struct vhost_net *n)
>diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
>index a09dedc79f68..1a8ab1d8cb1c 100644
>--- a/drivers/vhost/test.c
>+++ b/drivers/vhost/test.c
>@@ -146,7 +146,7 @@ static void vhost_test_stop(struct vhost_test *n, void **privatep)
>
> static void vhost_test_flush_vq(struct vhost_test *n, int index)
> {
>-	vhost_poll_flush(&n->vqs[index].poll);
>+	vhost_work_dev_flush(n->vqs[index].poll.dev);
> }
>
> static void vhost_test_flush(struct vhost_test *n)
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index 59edb5a1ffe2..ca088481da0e 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -245,14 +245,6 @@ void vhost_work_dev_flush(struct vhost_dev *dev)
> }
> EXPORT_SYMBOL_GPL(vhost_work_dev_flush);
>
>-/* Flush any work that has been scheduled. When calling this, don't hold any
>- * locks that are also used by the callback. */
>-void vhost_poll_flush(struct vhost_poll *poll)
>-{
>-	vhost_work_dev_flush(poll->dev);
>-}
>-EXPORT_SYMBOL_GPL(vhost_poll_flush);
>-

We should remove also the declaration in vhost.h:

--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -45,7 +44,6 @@ void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
                      __poll_t mask, struct vhost_dev *dev);
  int vhost_poll_start(struct vhost_poll *poll, struct file *file);
  void vhost_poll_stop(struct vhost_poll *poll);
-void vhost_poll_flush(struct vhost_poll *poll);
  void vhost_poll_queue(struct vhost_poll *poll);
  void vhost_work_dev_flush(struct vhost_dev *dev);


> void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
> {
> 	if (!dev->worker)
>@@ -663,7 +655,7 @@ void vhost_dev_stop(struct vhost_dev *dev)
> 	for (i = 0; i < dev->nvqs; ++i) {
> 		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
> 			vhost_poll_stop(&dev->vqs[i]->poll);
>-			vhost_poll_flush(&dev->vqs[i]->poll);
>+			vhost_work_dev_flush(dev->vqs[i]->poll.dev);
> 		}
> 	}
> }
>@@ -1712,7 +1704,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
> 	mutex_unlock(&vq->mutex);
>
> 	if (pollstop && vq->handle_kick)
>-		vhost_poll_flush(&vq->poll);
>+		vhost_work_dev_flush(vq->poll.dev);
> 	return r;
> }
> EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 938aefbc75ec..b0361ebbd695 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -711,7 +711,7 @@ static void vhost_vsock_flush(struct vhost_vsock *vsock)
>
> 	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++)
> 		if (vsock->vqs[i].handle_kick)
>-			vhost_poll_flush(&vsock->vqs[i].poll);
>+			vhost_work_dev_flush(vsock->vqs[i].poll.dev);
> 	vhost_work_dev_flush(&vsock->dev);
> }
>
>-- 
>2.32.0
>

The rest LGTM.

Thanks,
Stefano

[1] 
https://lore.kernel.org/virtualization/20211104190502.7053-1-michael.christie@oracle.com/