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SubjectRe: [PATCH v5 10/13] xen/pvcalls: implement recvmsg
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On 10/19/2017 09:38 PM, Stefano Stabellini wrote:
> On Tue, 17 Oct 2017, Boris Ostrovsky wrote:
>>> +
>>> +int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>>> + int flags)
>>> +{
>>> + struct pvcalls_bedata *bedata;
>>> + int ret;
>>> + struct sock_mapping *map;
>>> +
>>> + if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
>>> + return -EOPNOTSUPP;
>>> +
>>> + pvcalls_enter();
>>> + if (!pvcalls_front_dev) {
>>> + pvcalls_exit();
>>> + return -ENOTCONN;
>>> + }
>>> + 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);
>>> +
>>> + while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
>>> + wait_event_interruptible(map->active.inflight_conn_req,
>>> + pvcalls_front_read_todo(map));
>>> + }
>>> + ret = __read_ring(map->active.ring, &map->active.data,
>>> + &msg->msg_iter, len, flags);
>>> +
>>> + if (ret > 0)
>>> + notify_remote_via_irq(map->active.irq);
>>> + if (ret == 0)
>>> + ret = -EAGAIN;
>> Why not 0? The manpage says:
>>
>> EAGAIN or EWOULDBLOCK
>> The socket is marked nonblocking and the receive
>> operation would block, or a receive timeout
>> had been set and the timeout expired before data was
>> received. POSIX.1 allows either error to
>> be returned for this case, and does not require these
>> constants to have the same value, so a
>> portable application should check for both possibilities.
>>
>>
>> I don't think either of these conditions is true here.
>>
>> (Again, should have noticed this earlier, sorry)
> In case the socket is MSG_DONTWAIT, then we should return -EAGAIN here.
> However, it is true that if the socket is not MSG_DONTWAIT, then
> returning 0 would make more sense.
>
> So I'll do:
>
> if (ret == 0)
> ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;

Sure. With that

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

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