On 11/17/21 12:18, Mina Almasry wrote:
...
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
...
> @@ -288,11 +317,21 @@ static void __hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> struct hugetlb_cgroup *h_cg,
> struct page *page, bool rsvd)
> {
> + unsigned long *usage;
> +
I assume the use of a pointer is just to make the following WRITE_ONCE
look better? I prefer the suggestion by Muchun:
unsigned long usage = h_cg->nodeinfo[page_to_nid(page)]->usage[idx];
usage += nr_pages;
WRITE_ONCE(h_cg->nodeinfo[page_to_nid(page)]->usage[idx], usage);
I had to think for just a second 'why are we using/passing a pointer?'.
Not insisting we use Muchun's suggestion, it just caused me to think
a little more than necessary.
In any case, I would move the variable usage inside the
'if (!rsvd)' block.
> if (hugetlb_cgroup_disabled() || !h_cg)
> return;
>
> __set_hugetlb_cgroup(page, h_cg, rsvd);
> - return;
> + if (!rsvd) {
> + usage = &h_cg->nodeinfo[page_to_nid(page)]->usage[idx];
> + /*
> + * This write is not atomic due to fetching *usage and writing
> + * to it, but that's fine because we call this with
> + * hugetlb_lock held anyway.
> + */
> + WRITE_ONCE(*usage, *usage + nr_pages);
> + }
> }
>
> void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> @@ -316,6 +355,7 @@ static void __hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
> struct page *page, bool rsvd)
> {
> struct hugetlb_cgroup *h_cg;
> + unsigned long *usage;
Same here.
Otherwise, looks good to me.
--
Mike Kravetz
