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Message-Id: <1358351078-58915-3-git-send-email-jasowang@redhat.com>
Date: Wed, 16 Jan 2013 23:44:37 +0800
From: Jason Wang <jasowang@...hat.com>
To: davem@...emloft.net, mst@...hat.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Jason Wang <jasowang@...hat.com>
Subject: [PATCH V6 2/3] vhost_net: handle polling errors when setting backend
Currently, the polling errors were ignored, which can lead following issues:
- vhost remove itself unconditionally from waitqueue when stopping the poll,
this may crash the kernel since the previous attempt of starting may fail to
add itself to the waitqueue
- userspace may think the backend were successfully set even when the polling
failed.
Solve this by:
- check poll->wqh before trying to remove from waitqueue
- report polling errors in vhost_poll_start(), tx_poll_start(), the return value
will be checked and returned when userspace want to set the backend
After this fix, there still could be a polling failure after backend is set, it
will addressed by the next patch.
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
drivers/vhost/net.c | 27 ++++++++++++++++++---------
drivers/vhost/vhost.c | 18 +++++++++++++++---
drivers/vhost/vhost.h | 2 +-
3 files changed, 34 insertions(+), 13 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index d10ad6f..959b1cd 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -165,12 +165,16 @@ static void tx_poll_stop(struct vhost_net *net)
}
/* Caller must have TX VQ lock */
-static void tx_poll_start(struct vhost_net *net, struct socket *sock)
+static int tx_poll_start(struct vhost_net *net, struct socket *sock)
{
+ int ret;
+
if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))
- return;
- vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
- net->tx_poll_state = VHOST_NET_POLL_STARTED;
+ return 0;
+ ret = vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
+ if (!ret)
+ net->tx_poll_state = VHOST_NET_POLL_STARTED;
+ return ret;
}
/* In case of DMA done not in order in lower device driver for some reason.
@@ -642,20 +646,23 @@ static void vhost_net_disable_vq(struct vhost_net *n,
vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);
}
-static void vhost_net_enable_vq(struct vhost_net *n,
+static int vhost_net_enable_vq(struct vhost_net *n,
struct vhost_virtqueue *vq)
{
struct socket *sock;
+ int ret;
sock = rcu_dereference_protected(vq->private_data,
lockdep_is_held(&vq->mutex));
if (!sock)
- return;
+ return 0;
if (vq == n->vqs + VHOST_NET_VQ_TX) {
n->tx_poll_state = VHOST_NET_POLL_STOPPED;
- tx_poll_start(n, sock);
+ ret = tx_poll_start(n, sock);
} else
- vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
+ ret = vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
+
+ return ret;
}
static struct socket *vhost_net_stop_vq(struct vhost_net *n,
@@ -833,7 +840,9 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
r = vhost_init_used(vq);
if (r)
goto err_used;
- vhost_net_enable_vq(n, vq);
+ r = vhost_net_enable_vq(n, vq);
+ if (r)
+ goto err_used;
oldubufs = vq->ubufs;
vq->ubufs = ubufs;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 34389f7..9759249 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -77,26 +77,38 @@ void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
init_poll_funcptr(&poll->table, vhost_poll_func);
poll->mask = mask;
poll->dev = dev;
+ poll->wqh = NULL;
vhost_work_init(&poll->work, fn);
}
/* Start polling a file. We add ourselves to file's wait queue. The caller must
* keep a reference to a file until after vhost_poll_stop is called. */
-void vhost_poll_start(struct vhost_poll *poll, struct file *file)
+int vhost_poll_start(struct vhost_poll *poll, struct file *file)
{
unsigned long mask;
+ int ret = 0;
mask = file->f_op->poll(file, &poll->table);
if (mask)
vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
+ if (mask & POLLERR) {
+ if (poll->wqh)
+ remove_wait_queue(poll->wqh, &poll->wait);
+ ret = -EINVAL;
+ }
+
+ return ret;
}
/* Stop polling a file. After this function returns, it becomes safe to drop the
* file reference. You must also flush afterwards. */
void vhost_poll_stop(struct vhost_poll *poll)
{
- remove_wait_queue(poll->wqh, &poll->wait);
+ if (poll->wqh) {
+ remove_wait_queue(poll->wqh, &poll->wait);
+ poll->wqh = NULL;
+ }
}
static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
@@ -792,7 +804,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
fput(filep);
if (pollstart && vq->handle_kick)
- vhost_poll_start(&vq->poll, vq->kick);
+ r = vhost_poll_start(&vq->poll, vq->kick);
mutex_unlock(&vq->mutex);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 2639c58..17261e2 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -42,7 +42,7 @@ void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
unsigned long mask, struct vhost_dev *dev);
-void vhost_poll_start(struct vhost_poll *poll, struct file *file);
+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);
--
1.7.1
--
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