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SubjectRe: [PATCH 1/2] pvcalls-front: introduce a per sock_mapping refcount
On Mon, 12 Feb 2018, Juergen Gross wrote:
> 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@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)
>
> Did you mean:
> if (!pvcalls_front_dev || !pvcalls_front_dev->dev)

I actually meant:

if (!pvcalls_front_dev || dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)


> > + return ERR_PTR(-ENOTCONN);
> > +
> > + pvcalls_enter();
> > + map = (struct sock_mapping *) sock->sk->sk_send_head;
>
> Style: no blank after the cast, please (multiple times).

OK, I'll fix them all


> > + 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;
> }

Sounds good.

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