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SubjectRe: [RFC v1 08/14] bus1: implement peer management context
On Fri, Oct 28, 2016 at 3:05 PM, Richard Weinberger
<richard.weinberger@gmail.com> wrote:
> On Wed, Oct 26, 2016 at 9:18 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
>> + /* initialize constant fields */
>> + peer->id = atomic64_inc_return(&peer_ids);
>> + peer->flags = 0;
>> + peer->cred = get_cred(current_cred());
>> + peer->pid_ns = get_pid_ns(task_active_pid_ns(current));
>> + peer->user = user;
>> + peer->debugdir = NULL;
>> + init_waitqueue_head(&peer->waitq);
>> + bus1_active_init(&peer->active);
>> +
>> + /* initialize data section */
>> + mutex_init(&peer->data.lock);
>> +
>> + /* initialize peer-private section */
>> + mutex_init(&peer->local.lock);
>> +
>> + if (!IS_ERR_OR_NULL(bus1_debugdir)) {
>
> How can bus1_debugdir contain an error code? AFACT it is either a
> valid dentry or NULL.

If debugfs is not enabled it will be ERR_PTR(-ENODEV).

>> + char idstr[22];
>> +
>> + snprintf(idstr, sizeof(idstr), "peer-%llx", peer->id);
>> +
>> + peer->debugdir = debugfs_create_dir(idstr, bus1_debugdir);
>> + if (!peer->debugdir) {
>> + pr_err("cannot create debugfs dir for peer %llx\n",
>> + peer->id);
>> + } else if (!IS_ERR_OR_NULL(peer->debugdir)) {
>> + bus1_debugfs_create_atomic_x("active", S_IRUGO,
>> + peer->debugdir,
>> + &peer->active.count);
>> + }
>> + }
>> +
>> + bus1_active_activate(&peer->active);
>
> This is a no-nop since bus1_active_init() set ->count to BUS1_ACTIVE_NEW.

bus1_active_activate() changes count from BUS1_ACTIVE_NEW to 0.

>> + return peer;
>> +}
>> +
>> +static int bus1_peer_disconnect(struct bus1_peer *peer)
>> +{
>> + bus1_active_deactivate(&peer->active);
>> + bus1_active_drain(&peer->active, &peer->waitq);
>> +
>> + if (!bus1_active_cleanup(&peer->active, &peer->waitq,
>> + NULL, NULL))
>> + return -ESHUTDOWN;
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * bus1_peer_free() - destroy peer
>> + * @peer: peer to destroy, or NULL
>> + *
>> + * Destroy a peer object that was previously allocated via bus1_peer_new().
>> + * This synchronously waits for any outstanding operations on this peer to
>> + * finish, then releases all linked resources and deallocates the peer in an
>> + * rcu-delayed manner.
>> + *
>> + * If NULL is passed, this is a no-op.
>> + *
>> + * Return: NULL is returned.
>
> What about making the function of type void?

We are consistently returning the type being freed so we can do

foo->bar = bar_free(bar);

Just a matter of style though.

>> +struct bus1_peer *bus1_peer_free(struct bus1_peer *peer)
>> +{
>> + if (!peer)
>> + return NULL;
>> +
>> + /* disconnect from environment */
>> + bus1_peer_disconnect(peer);
>> +
>> + /* deinitialize peer-private section */
>> + mutex_destroy(&peer->local.lock);
>> +
>> + /* deinitialize data section */
>> + mutex_destroy(&peer->data.lock);
>> +
>> + /* deinitialize constant fields */
>> + debugfs_remove_recursive(peer->debugdir);
>> + bus1_active_deinit(&peer->active);
>> + peer->user = bus1_user_unref(peer->user);
>> + put_pid_ns(peer->pid_ns);
>> + put_cred(peer->cred);
>> + kfree_rcu(peer, rcu);
>> +
>> + return NULL;
>> +}
>
> --
> Thanks,
> //richard

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