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Subject[PATCH RFC tip/core/rcu 19/30] vhost: add __rcu annotations
Date
From: Arnd Bergmann <arnd@relay.de.ibm.com>

Also add rcu_dreference_protected() for code paths where locks are held.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
---
drivers/vhost/net.c | 15 +++++++++++----
drivers/vhost/vhost.c | 29 +++++++++++++++++++++++------
drivers/vhost/vhost.h | 11 ++++++++---
3 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index df5b6b9..e044dd0 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -110,7 +110,9 @@ static void handle_tx(struct vhost_net *net)
size_t len, total_len = 0;
int err, wmem;
size_t hdr_size;
- struct socket *sock = rcu_dereference(vq->private_data);
+ struct socket *sock;
+
+ sock = rcu_dereference_check(vq->private_data, in_vhost_workqueue());
if (!sock)
return;

@@ -364,7 +366,10 @@ static void vhost_net_disable_vq(struct vhost_net *n,
static void vhost_net_enable_vq(struct vhost_net *n,
struct vhost_virtqueue *vq)
{
- struct socket *sock = vq->private_data;
+ struct socket *sock;
+
+ sock = rcu_dereference_protected(vq->private_data,
+ lockdep_is_held(&vq->mutex));
if (!sock)
return;
if (vq == n->vqs + VHOST_NET_VQ_TX) {
@@ -380,7 +385,8 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n,
struct socket *sock;

mutex_lock(&vq->mutex);
- sock = vq->private_data;
+ sock = rcu_dereference_protected(vq->private_data,
+ lockdep_is_held(&vq->mutex));
vhost_net_disable_vq(n, vq);
rcu_assign_pointer(vq->private_data, NULL);
mutex_unlock(&vq->mutex);
@@ -518,7 +524,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
}

/* start polling new socket */
- oldsock = vq->private_data;
+ oldsock = rcu_dereference_protected(vq->private_data,
+ lockdep_is_held(&vq->mutex));
if (sock == oldsock)
goto done;

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 3b83382..aa7603a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -39,6 +39,13 @@ enum {

static struct workqueue_struct *vhost_workqueue;

+#ifdef CONFIG_PROVE_RCU
+int in_vhost_workqueue(void)
+{
+ return in_workqueue_context(vhost_workqueue);
+}
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
{
@@ -180,7 +187,7 @@ long vhost_dev_reset_owner(struct vhost_dev *dev)
vhost_dev_cleanup(dev);

memory->nregions = 0;
- dev->memory = memory;
+ RCU_INIT_POINTER(dev->memory, memory);
return 0;
}

@@ -212,8 +219,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
fput(dev->log_file);
dev->log_file = NULL;
/* No one will access memory at this point */
- kfree(dev->memory);
- dev->memory = NULL;
+ kfree(rcu_dereference_protected(dev->memory,
+ lockdep_is_held(&dev->mutex)));
+ RCU_INIT_POINTER(dev->memory, NULL);
if (dev->mm)
mmput(dev->mm);
dev->mm = NULL;
@@ -294,14 +302,22 @@ static int vq_access_ok(unsigned int num,
/* Caller should have device mutex but not vq mutex */
int vhost_log_access_ok(struct vhost_dev *dev)
{
- return memory_access_ok(dev, dev->memory, 1);
+ struct vhost_memory *mp;
+
+ mp = rcu_dereference_protected(dev->memory,
+ lockdep_is_held(&dev->mutex));
+ return memory_access_ok(dev, mp, 1);
}

/* Verify access for write logging. */
/* Caller should have vq mutex and device mutex */
static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
{
- return vq_memory_access_ok(log_base, vq->dev->memory,
+ struct vhost_memory *mp;
+
+ mp = rcu_dereference_protected(vq->dev->memory,
+ lockdep_is_held(&vq->mutex));
+ return vq_memory_access_ok(log_base, mp,
vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
(!vq->log_used || log_access_ok(log_base, vq->log_addr,
sizeof *vq->used +
@@ -341,7 +357,8 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
kfree(newmem);
return -EFAULT;
}
- oldmem = d->memory;
+ oldmem = rcu_dereference_protected(d->memory,
+ lockdep_is_held(&d->mutex));
rcu_assign_pointer(d->memory, newmem);
synchronize_rcu();
kfree(oldmem);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 44591ba..48fb0ff 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -92,7 +92,7 @@ struct vhost_virtqueue {
* work item execution acts instead of rcu_read_lock() and the end of
* work item execution acts instead of rcu_read_lock().
* Writers use virtqueue mutex. */
- void *private_data;
+ void __rcu *private_data;
/* Log write descriptors */
void __user *log_base;
struct vhost_log log[VHOST_NET_MAX_SG];
@@ -102,7 +102,7 @@ struct vhost_dev {
/* Readers use RCU to access memory table pointer
* log base pointer and features.
* Writers use mutex below.*/
- struct vhost_memory *memory;
+ struct vhost_memory __rcu *memory;
struct mm_struct *mm;
struct mutex mutex;
unsigned acked_features;
@@ -112,6 +112,7 @@ struct vhost_dev {
struct eventfd_ctx *log_ctx;
};

+int in_vhost_workqueue(void);
long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nvqs);
long vhost_dev_check_owner(struct vhost_dev *);
long vhost_dev_reset_owner(struct vhost_dev *);
@@ -154,7 +155,11 @@ enum {

static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
{
- unsigned acked_features = rcu_dereference(dev->acked_features);
+ unsigned acked_features;
+
+ acked_features =
+ rcu_dereference_index_check(dev->acked_features,
+ lockdep_is_held(&dev->mutex));
return acked_features & (1 << bit);
}

--
1.7.0.6


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