Cc Andrew (original patch is here
http://lkml.kernel.org/r/20190104183726.GA6374@embeddedor)
On Fri 04-01-19 12:37:26, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct foo {
> int stuff;
> void *entry[];
> };
>
> instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
This looks indeed neater
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Thanks
> ---
> mm/memcontrol.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index af7f18b32389..ad256cf7da47 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3626,8 +3626,7 @@ static int __mem_cgroup_usage_register_event(struct
> mem_cgroup *memcg,
> size = thresholds->primary ? thresholds->primary->size + 1 : 1;
>
> /* Allocate memory for new array of thresholds */
> - new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
> - GFP_KERNEL);
> + new = kmalloc(struct_size(new, entries, size), GFP_KERNEL);
> if (!new) {
> ret = -ENOMEM;
> goto unlock;
> --
> 2.20.1
--
Michal Hocko
SUSE Labs
