On Thu, 2020-10-01 at 09:56 -0500, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> struct uv_rtc_timer_head contains a one-element array cpu[1].
>
> Switch it to a flexible array and use the struct_size() helper to
> calculate the allocation size. Also, save some heap space in the
> process[3].
trivia:
> diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
[]
> @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void)
> struct uv_rtc_timer_head *head = blade_info[bid];
>
> if (!head) {
> - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) +
> - (uv_blade_nr_possible_cpus(bid) *
> - 2 * sizeof(u64)),
> + head = kmalloc_node(struct_size(head, cpu,
> + uv_blade_nr_possible_cpus(bid)),
> GFP_KERNEL, nid);
> if (!head) {
> uv_rtc_deallocate_timers();
Maybe save the value of uv_blade_nr_possible_cpus(bid)
to reduce duplication and make the sizeof_struct more
readable?
if (!head) {
int ncpus = uv_blade_nr_possible_cpus(bid);
head = kmalloc_node(struct_size(head, cpu, ncpus),
GFP_KERNEL, nid);
if (!head) {
uv_rtc_deallocate_timers();
return -ENOMEM;
}
spin_lock_init(&head->lock);
head->ncpus = ncpus;
head->next_cpu = -1;
blade_info[bid] = head;
}
