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Subject[PATCH 1/2] pvcalls-front: introduce a per sock_mapping refcount
Date
Introduce a per sock_mapping refcount, in addition to the existing
global refcount. Thanks to the sock_mapping refcount, we can safely wait
for it to be 1 in pvcalls_front_release before freeing an active socket,
instead of waiting for the global refcount to be 1.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
---
drivers/xen/pvcalls-front.c | 190 ++++++++++++++++++--------------------------
1 file changed, 78 insertions(+), 112 deletions(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 4c789e6..164d3ad 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -60,6 +60,7 @@ struct sock_mapping {
bool active_socket;
struct list_head list;
struct socket *sock;
+ atomic_t refcount;
union {
struct {
int irq;
@@ -93,6 +94,33 @@ struct sock_mapping {
};
};

+static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
+{
+ struct sock_mapping *map = NULL;
+
+ if (!pvcalls_front_dev || &pvcalls_front_dev->dev == NULL)
+ return ERR_PTR(-ENOTCONN);
+
+ pvcalls_enter();
+ map = (struct sock_mapping *) sock->sk->sk_send_head;
+ if (map == NULL) {
+ pvcalls_exit()
+ return ERR_PTR(-ENOTSOCK);
+ }
+
+ atomic_inc(&map->refcount);
+ return map;
+}
+
+static inline void pvcalls_exit_sock(struct socket *sock)
+{
+ struct sock_mapping *map = NULL;
+
+ map = (struct sock_mapping *) sock->sk->sk_send_head;
+ atomic_dec(&map->refcount);
+ pvcalls_exit();
+}
+
static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
{
*req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
@@ -369,31 +397,23 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
return -EOPNOTSUPP;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
- return -ENOTCONN;
- }
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
+ return PTR_ERR(map);

bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *)sock->sk->sk_send_head;
- if (!map) {
- pvcalls_exit();
- return -ENOTSOCK;
- }
-
spin_lock(&bedata->socket_lock);
ret = get_request(bedata, &req_id);
if (ret < 0) {
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}
ret = create_active(map, &evtchn);
if (ret < 0) {
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}

@@ -423,7 +443,7 @@ int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
smp_rmb();
ret = bedata->rsp[req_id].ret;
bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}

@@ -488,23 +508,15 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
return -EOPNOTSUPP;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
- return -ENOTCONN;
- }
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (!map) {
- pvcalls_exit();
- return -ENOTSOCK;
- }
-
mutex_lock(&map->active.out_mutex);
if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
mutex_unlock(&map->active.out_mutex);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EAGAIN;
}
if (len > INT_MAX)
@@ -526,7 +538,7 @@ int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
tot_sent = sent;

mutex_unlock(&map->active.out_mutex);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return tot_sent;
}

@@ -591,19 +603,11 @@ int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
return -EOPNOTSUPP;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
- return -ENOTCONN;
- }
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (!map) {
- pvcalls_exit();
- return -ENOTSOCK;
- }
-
mutex_lock(&map->active.in_mutex);
if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
@@ -623,7 +627,7 @@ int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
ret = 0;

mutex_unlock(&map->active.in_mutex);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}

@@ -637,24 +641,16 @@ int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
return -EOPNOTSUPP;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
- return -ENOTCONN;
- }
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (map == NULL) {
- pvcalls_exit();
- return -ENOTSOCK;
- }
-
spin_lock(&bedata->socket_lock);
ret = get_request(bedata, &req_id);
if (ret < 0) {
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}
req = RING_GET_REQUEST(&bedata->ring, req_id);
@@ -684,7 +680,7 @@ int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;

map->passive.status = PVCALLS_STATUS_BIND;
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return 0;
}

@@ -695,21 +691,13 @@ int pvcalls_front_listen(struct socket *sock, int backlog)
struct xen_pvcalls_request *req;
int notify, req_id, ret;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
- return -ENOTCONN;
- }
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (!map) {
- pvcalls_exit();
- return -ENOTSOCK;
- }
-
if (map->passive.status != PVCALLS_STATUS_BIND) {
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EOPNOTSUPP;
}

@@ -717,7 +705,7 @@ int pvcalls_front_listen(struct socket *sock, int backlog)
ret = get_request(bedata, &req_id);
if (ret < 0) {
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}
req = RING_GET_REQUEST(&bedata->ring, req_id);
@@ -741,7 +729,7 @@ int pvcalls_front_listen(struct socket *sock, int backlog)
bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;

map->passive.status = PVCALLS_STATUS_LISTEN;
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}

@@ -753,21 +741,13 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
struct xen_pvcalls_request *req;
int notify, req_id, ret, evtchn, nonblock;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
- return -ENOTCONN;
- }
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (!map) {
- pvcalls_exit();
- return -ENOTSOCK;
- }
-
if (map->passive.status != PVCALLS_STATUS_LISTEN) {
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EINVAL;
}

@@ -785,13 +765,13 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
goto received;
}
if (nonblock) {
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EAGAIN;
}
if (wait_event_interruptible(map->passive.inflight_accept_req,
!test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
(void *)&map->passive.flags))) {
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EINTR;
}
}
@@ -802,7 +782,7 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
(void *)&map->passive.flags);
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}
map2 = kzalloc(sizeof(*map2), GFP_ATOMIC);
@@ -810,7 +790,7 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
(void *)&map->passive.flags);
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -ENOMEM;
}
ret = create_active(map2, &evtchn);
@@ -819,7 +799,7 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
(void *)&map->passive.flags);
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}
list_add_tail(&map2->list, &bedata->socket_mappings);
@@ -841,13 +821,13 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
/* We could check if we have received a response before returning. */
if (nonblock) {
WRITE_ONCE(map->passive.inflight_req_id, req_id);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EAGAIN;
}

if (wait_event_interruptible(bedata->inflight_req,
READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -EINTR;
}
/* read req_id, then the content */
@@ -862,7 +842,7 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
(void *)&map->passive.flags);
pvcalls_front_free_map(bedata, map2);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return -ENOMEM;
}
newsock->sk->sk_send_head = (void *)map2;
@@ -874,7 +854,7 @@ int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
wake_up(&map->passive.inflight_accept_req);

- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}

@@ -965,23 +945,16 @@ unsigned int pvcalls_front_poll(struct file *file, struct socket *sock,
struct sock_mapping *map;
int ret;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map))
return POLLNVAL;
- }
bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (!map) {
- pvcalls_exit();
- return POLLNVAL;
- }
if (map->active_socket)
ret = pvcalls_front_poll_active(file, bedata, map, wait);
else
ret = pvcalls_front_poll_passive(file, bedata, map, wait);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}

@@ -995,25 +968,18 @@ int pvcalls_front_release(struct socket *sock)
if (sock->sk == NULL)
return 0;

- pvcalls_enter();
- if (!pvcalls_front_dev) {
- pvcalls_exit();
+ map = pvcalls_enter_sock(sock);
+ if (IS_ERR(map) && PTR_ERR(map) == -ENOTCONN)
return -EIO;
- }
-
- bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
-
- map = (struct sock_mapping *) sock->sk->sk_send_head;
- if (map == NULL) {
- pvcalls_exit();
+ if (IS_ERR(map) && PTR_ERR(map) == -ENOTSOCK)
return 0;
- }
+ bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

spin_lock(&bedata->socket_lock);
ret = get_request(bedata, &req_id);
if (ret < 0) {
spin_unlock(&bedata->socket_lock);
- pvcalls_exit();
+ pvcalls_exit_sock(sock);
return ret;
}
sock->sk->sk_send_head = NULL;
@@ -1043,10 +1009,10 @@ int pvcalls_front_release(struct socket *sock)
/*
* We need to make sure that sendmsg/recvmsg on this socket have
* not started before we've cleared sk_send_head here. The
- * easiest (though not optimal) way to guarantee this is to see
- * that no pvcall (other than us) is in progress.
+ * easiest way to guarantee this is to see that no pvcalls
+ * (other than us) is in progress on this socket.
*/
- while (atomic_read(&pvcalls_refcount) > 1)
+ while (atomic_read(&map->refcount) > 1)
cpu_relax();

pvcalls_front_free_map(bedata, map);
--
1.9.1
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