linux-kernel - Re: [PATCH v5 1/1] KVM: trigger uevents when creating or destroying a VM

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Date:   Mon, 17 Jul 2017 17:53:51 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Claudio Imbrenda <imbrenda@...ux.vnet.ibm.com>, kvm@...r.kernel.org
Cc:     borntraeger@...ibm.com, pbonzini@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/1] KVM: trigger uevents when creating or destroying a
 VM


> +	add_uevent_var(env, "CREATED=%llu", created);
> +	add_uevent_var(env, "COUNT=%llu", active);

I like that much better.

> +
> +	if (type == KVM_EVENT_CREATE_VM)
> +		add_uevent_var(env, "EVENT=create");
> +	else if (type == KVM_EVENT_DESTROY_VM)
> +		add_uevent_var(env, "EVENT=destroy");
> +
> +	if (kvm->debugfs_dentry) {
> +		char p[ITOA_MAX_LEN];

I'd move this also to the top of the function. Or move tmp and pathbuf
in here, so you could also move them to this place.

> +
> +		snprintf(p, sizeof(p), "%s", kvm->debugfs_dentry->d_name.name);

Probably just me, but I prefer ARRAY_SIZE() instead of sizeof() for any
kind of array sizes.

> +		tmp = strchrnul(p + 1, '-');> +		*tmp = '\0';
> +		add_uevent_var(env, "PID=%s", p);
> +		pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
> +		if (pathbuf) {
> +			/* sizeof counts the final '\0' */
> +			int len = sizeof("STATS_PATH=") - 1;
> +			const char *pvar = "STATS_PATH=";

Can't you avoid that? See next paragraph.


> +
> +			tmp = dentry_path_raw(kvm->debugfs_dentry,
> +					      pathbuf + len,
> +					      PATH_MAX - len);
> +			if (!IS_ERR(tmp)) {

Why not

tmp = dentry_path_raw(kvm->debugfs_dentry, pathbuf, PATH_MAX);
if (!IS_ERR(tmp)) {
	add_uevent_var(env, "STATS_PATH=s", tmp);
}

and avoid len / pvar / memcpy? And keep internal env size checking
consistent.

(are my tired eyes missing something? :) )


> +				memcpy(tmp - len, pvar, len);
> +				env->envp[env->envp_idx++] = tmp - len;
> +			}
> +		}
> +	}
> +	/* no need for checks, since we are adding at most only 5 keys */
> +	env->envp[env->envp_idx++] = NULL;
> +	kobject_uevent_env(&kvm_dev.this_device->kobj, KOBJ_CHANGE, env->envp);
> +	kfree(env);
> +	kfree(pathbuf);
> +}
> +
>  static int kvm_init_debug(void)
>  {
>  	int r = -EEXIST;
> 


-- 

Thanks,

David