Virtualization - May 2022 - [PATCH V3 4/8] vhost_test: remove vhost_test_flush_vq()

The following patches made over linus's/mst's tree are Andrey
Ryabinin's
flush cleanups and some from me. They reduce the number of flush calls
and remove some bogus ones where we don't even have a worker running
anymore or they were based on outdated or incorrect assumptions.

V3:
- Fix test.c flush use.

V2:
- Added patch to rename vhost_work_dev_flush to just vhost_dev_flush
to handle review comment from Jason about the naming not being so
great.

From: Andrey Ryabinin <arbn at yandex-team.com>

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 at yandex-team.com>
[merge vhost_poll_flush removal from Stefano Garzarella]
Signed-off-by: Mike Christie <michael.christie at oracle.com>
Reviewed-by: Chaitanya Kulkarni <kch at nvidia.com>
Acked-by: Jason Wang <jasowang at redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
---
 drivers/vhost/net.c   |  4 ++--
 drivers/vhost/test.c  |  2 +-
 drivers/vhost/vhost.c | 12 ++----------
 drivers/vhost/vhost.h |  1 -
 drivers/vhost/vsock.c |  2 +-
 5 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 792ab5f23647..4e55ad8c942a 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1376,8 +1376,8 @@ 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 05740cba1cd8..f0ac9e35f5d6 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 d02173fb290c..1d84a2818c6f 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);
-
 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);
 		}
 	}
 }
@@ -1719,7 +1711,7 @@ 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/vhost.h b/drivers/vhost/vhost.h
index 638bb640d6b4..aeb8e1ad1496 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -44,7 +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);
 
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index e6c9d41db1de..a4c8ae92a0fb 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -709,7 +709,7 @@ 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);
 }
 
-- 
2.25.1

When vhost_work_dev_flush returns all work queued at that time will have
completed. There is then no need to flush after every vhost_poll_stop
call, and we can move the flush call to after the loop that stops the
pollers.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
Acked-by: Jason Wang <jasowang at redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
---
 drivers/vhost/vhost.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1d84a2818c6f..9f8de04bb673 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -653,11 +653,11 @@ void vhost_dev_stop(struct vhost_dev *dev)
 	int i;
 
 	for (i = 0; i < dev->nvqs; ++i) {
-		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
+		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick)
 			vhost_poll_stop(&dev->vqs[i]->poll);
-			vhost_work_dev_flush(dev->vqs[i]->poll.dev);
-		}
 	}
+
+	vhost_work_dev_flush(dev);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_stop);
 
-- 
2.25.1

From: Andrey Ryabinin <arbn at yandex-team.com>

vhost_net_flush_vq() calls vhost_work_dev_flush() twice passing
vhost_dev pointer obtained via 'n->poll[index].dev' and
'n->vqs[index].vq.poll.dev'. This is actually the same pointer,
initialized in vhost_net_open()/vhost_dev_init()/vhost_poll_init()

Remove vhost_net_flush_vq() and call vhost_work_dev_flush() directly.
Do the flushes only once instead of several flush calls in a row
which seems rather useless.

Signed-off-by: Andrey Ryabinin <arbn at yandex-team.com>
[drop vhost_dev forward declaration in vhost.h]
Signed-off-by: Mike Christie <michael.christie at oracle.com>
Acked-by: Jason Wang <jasowang at redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
---
 drivers/vhost/net.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 4e55ad8c942a..047b7b05109a 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1374,16 +1374,9 @@ static void vhost_net_stop(struct vhost_net *n, struct
socket **tx_sock,
 	*rx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_RX].vq);
 }
 
-static void vhost_net_flush_vq(struct vhost_net *n, int index)
-{
-	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)
 {
-	vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
-	vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
+	vhost_work_dev_flush(&n->dev);
 	if (n->vqs[VHOST_NET_VQ_TX].ubufs) {
 		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
 		n->tx_flush = true;
@@ -1573,7 +1566,7 @@ static long vhost_net_set_backend(struct vhost_net *n,
unsigned index, int fd)
 	}
 
 	if (oldsock) {
-		vhost_net_flush_vq(n, index);
+		vhost_work_dev_flush(&n->dev);
 		sockfd_put(oldsock);
 	}
 
-- 
2.25.1

From: Andrey Ryabinin <arbn at yandex-team.com>

vhost_test_flush_vq() just a simple wrapper around vhost_work_dev_flush()
which seems have no value. It's just easier to call vhost_work_dev_flush()
directly. Besides there is no point in obtaining vhost_dev pointer
via 'n->vqs[index].poll.dev' while we can just use &n->dev.
It's the same pointers, see vhost_test_open()/vhost_dev_init().

Signed-off-by: Andrey Ryabinin <arbn at yandex-team.com>
Signed-off-by: Mike Christie <michael.christie at oracle.com>
Reviewed-by: Chaitanya Kulkarni <kch at nvidia.com>
Acked-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/test.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index f0ac9e35f5d6..de39151366c5 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -144,14 +144,9 @@ static void vhost_test_stop(struct vhost_test *n, void
**privatep)
 	*privatep = vhost_test_stop_vq(n, n->vqs + VHOST_TEST_VQ);
 }
 
-static void vhost_test_flush_vq(struct vhost_test *n, int index)
-{
-	vhost_work_dev_flush(n->vqs[index].poll.dev);
-}
-
 static void vhost_test_flush(struct vhost_test *n)
 {
-	vhost_test_flush_vq(n, VHOST_TEST_VQ);
+	vhost_work_dev_flush(&n->dev);
 }
 
 static int vhost_test_release(struct inode *inode, struct file *f)
@@ -210,7 +205,7 @@ static long vhost_test_run(struct vhost_test *n, int test)
 			goto err;
 
 		if (oldpriv) {
-			vhost_test_flush_vq(n, index);
+			vhost_test_flush(n);
 		}
 	}
 
@@ -303,7 +298,7 @@ static long vhost_test_set_backend(struct vhost_test *n,
unsigned index, int fd)
 	mutex_unlock(&vq->mutex);
 
 	if (enable) {
-		vhost_test_flush_vq(n, index);
+		vhost_test_flush(n);
 	}
 
 	mutex_unlock(&n->dev.mutex);
-- 
2.25.1

From: Andrey Ryabinin <arbn at yandex-team.com>

vhost_vsock_flush() calls vhost_work_dev_flush(vsock->vqs[i].poll.dev)
before vhost_work_dev_flush(&vsock->dev). This seems pointless
as vsock->vqs[i].poll.dev is the same as &vsock->dev and several
flushes
in a row doesn't do anything useful, one is just enough.

Signed-off-by: Andrey Ryabinin <arbn at yandex-team.com>
Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
Signed-off-by: Mike Christie <michael.christie at oracle.com>
Acked-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/vsock.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index a4c8ae92a0fb..96be63697117 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -705,11 +705,6 @@ static int vhost_vsock_dev_open(struct inode *inode, struct
file *file)
 
 static void vhost_vsock_flush(struct vhost_vsock *vsock)
 {
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++)
-		if (vsock->vqs[i].handle_kick)
-			vhost_work_dev_flush(vsock->vqs[i].poll.dev);
 	vhost_work_dev_flush(&vsock->dev);
 }
 
-- 
2.25.1

The flush after vhost_dev_cleanup is not needed because:

1. It doesn't do anything. vhost_dev_cleanup will stop the worker thread
so the flush call will just return since the worker has not device.

2. It's not needed for the re-queue case. vhost_scsi_evt_handle_kick grabs
the mutex and if the backend is NULL will return without queueing a work.
vhost_scsi_clear_endpoint will set the backend to NULL under the vq->mutex
then drops the mutex and does a flush. So we know when
vhost_scsi_clear_endpoint has dropped the mutex after clearing the backend
no evt related work will be able to requeue. The flush would then make sure
any queued evts are run and return.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
Acked-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/scsi.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 532e204f2b1b..94535c813ef7 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1827,8 +1827,6 @@ static int vhost_scsi_release(struct inode *inode, struct
file *f)
 	vhost_scsi_clear_endpoint(vs, &t);
 	vhost_dev_stop(&vs->dev);
 	vhost_dev_cleanup(&vs->dev);
-	/* Jobs can re-queue themselves in evt kick handler. Do extra flush. */
-	vhost_scsi_flush(vs);
 	kfree(vs->dev.vqs);
 	kvfree(vs);
 	return 0;
-- 
2.25.1

The flush after vhost_dev_cleanup is not needed because:

1. It doesn't do anything. vhost_dev_cleanup will stop the worker thread
so the flush call will just return since the worker has not device.

2. It's not needed. The comment about jobs re-queueing themselves does
not look correct because handle_vq does not requeue work.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
Acked-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/test.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index de39151366c5..6c139f18bc54 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -158,9 +158,6 @@ static int vhost_test_release(struct inode *inode, struct
file *f)
 	vhost_test_flush(n);
 	vhost_dev_stop(&n->dev);
 	vhost_dev_cleanup(&n->dev);
-	/* We do an extra flush before freeing memory,
-	 * since jobs can re-queue themselves. */
-	vhost_test_flush(n);
 	kfree(n->dev.vqs);
 	kfree(n);
 	return 0;
-- 
2.25.1

This patch renames vhost_work_dev_flush to just vhost_dev_flush to
relfect that it flushes everything on the device and that drivers
don't know/care that polls are based on vhost_works. Drivers just
flush the entire device and polls, and works for vhost-scsi
management TMFs and IO net virtqueues, etc all are flushed.

Signed-off-by: Mike Christie <michael.christie at oracle.com>
Acked-by: Jason Wang <jasowang at redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
---
 drivers/vhost/net.c   |  4 ++--
 drivers/vhost/scsi.c  |  2 +-
 drivers/vhost/test.c  |  2 +-
 drivers/vhost/vhost.c | 10 +++++-----
 drivers/vhost/vhost.h |  2 +-
 drivers/vhost/vsock.c |  2 +-
 6 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 047b7b05109a..0e4ff6a08f5f 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1376,7 +1376,7 @@ static void vhost_net_stop(struct vhost_net *n, struct
socket **tx_sock,
 
 static void vhost_net_flush(struct vhost_net *n)
 {
-	vhost_work_dev_flush(&n->dev);
+	vhost_dev_flush(&n->dev);
 	if (n->vqs[VHOST_NET_VQ_TX].ubufs) {
 		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
 		n->tx_flush = true;
@@ -1566,7 +1566,7 @@ static long vhost_net_set_backend(struct vhost_net *n,
unsigned index, int fd)
 	}
 
 	if (oldsock) {
-		vhost_work_dev_flush(&n->dev);
+		vhost_dev_flush(&n->dev);
 		sockfd_put(oldsock);
 	}
 
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 94535c813ef7..ffd9e6c2ffc1 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1436,7 +1436,7 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
 		kref_put(&old_inflight[i]->kref, vhost_scsi_done_inflight);
 
 	/* Flush both the vhost poll and vhost work */
-	vhost_work_dev_flush(&vs->dev);
+	vhost_dev_flush(&vs->dev);
 
 	/* Wait for all reqs issued before the flush to be finished */
 	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 6c139f18bc54..bc8e7fb1e635 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(struct vhost_test *n)
 {
-	vhost_work_dev_flush(&n->dev);
+	vhost_dev_flush(&n->dev);
 }
 
 static int vhost_test_release(struct inode *inode, struct file *f)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9f8de04bb673..716a80c61fa9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -231,7 +231,7 @@ void vhost_poll_stop(struct vhost_poll *poll)
 }
 EXPORT_SYMBOL_GPL(vhost_poll_stop);
 
-void vhost_work_dev_flush(struct vhost_dev *dev)
+void vhost_dev_flush(struct vhost_dev *dev)
 {
 	struct vhost_flush_struct flush;
 
@@ -243,7 +243,7 @@ void vhost_work_dev_flush(struct vhost_dev *dev)
 		wait_for_completion(&flush.wait_event);
 	}
 }
-EXPORT_SYMBOL_GPL(vhost_work_dev_flush);
+EXPORT_SYMBOL_GPL(vhost_dev_flush);
 
 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 {
@@ -530,7 +530,7 @@ static int vhost_attach_cgroups(struct vhost_dev *dev)
 	attach.owner = current;
 	vhost_work_init(&attach.work, vhost_attach_cgroups_work);
 	vhost_work_queue(dev, &attach.work);
-	vhost_work_dev_flush(dev);
+	vhost_dev_flush(dev);
 	return attach.ret;
 }
 
@@ -657,7 +657,7 @@ void vhost_dev_stop(struct vhost_dev *dev)
 			vhost_poll_stop(&dev->vqs[i]->poll);
 	}
 
-	vhost_work_dev_flush(dev);
+	vhost_dev_flush(dev);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_stop);
 
@@ -1711,7 +1711,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *arg
 	mutex_unlock(&vq->mutex);
 
 	if (pollstop && vq->handle_kick)
-		vhost_work_dev_flush(vq->poll.dev);
+		vhost_dev_flush(vq->poll.dev);
 	return r;
 }
 EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index aeb8e1ad1496..d02adf1b2bf8 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -45,7 +45,7 @@ void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t
fn,
 int vhost_poll_start(struct vhost_poll *poll, struct file *file);
 void vhost_poll_stop(struct vhost_poll *poll);
 void vhost_poll_queue(struct vhost_poll *poll);
-void vhost_work_dev_flush(struct vhost_dev *dev);
+void vhost_dev_flush(struct vhost_dev *dev);
 
 struct vhost_log {
 	u64 addr;
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 96be63697117..368330417bde 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -705,7 +705,7 @@ static int vhost_vsock_dev_open(struct inode *inode, struct
file *file)
 
 static void vhost_vsock_flush(struct vhost_vsock *vsock)
 {
-	vhost_work_dev_flush(&vsock->dev);
+	vhost_dev_flush(&vsock->dev);
 }
 
 static void vhost_vsock_reset_orphans(struct sock *sk)
-- 
2.25.1