Re: [PATCH 1/2] pvcalls-front: introduce a per sock_mapping refcount

From: Juergen Gross
Date: Mon Feb 12 2018 - 08:15:03 EST

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On 05/02/18 23:51, Stefano Stabellini wrote:
> 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@xxxxxxxxxxx>
> ---
> 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)

Did you mean:
if (!pvcalls_front_dev || !pvcalls_front_dev->dev)

> + return ERR_PTR(-ENOTCONN);
> +
> + pvcalls_enter();
> + map = (struct sock_mapping *) sock->sk->sk_send_head;

Style: no blank after the cast, please (multiple times).

> + 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;

Hmm, what about:

if (IS_ERR(map)) {
if (PTR_ERR(map) == -ENOTCONN)
return -EIO;
else
return 0;
}

Juergen

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