On Tue 13-04-21 12:47:43, Oscar Salvador wrote:
> Currently, the clearing of the flag is done under the lock, but this
> is unnecessary as we just allocated the page and we did not give it
> away yet, so no one should be messing with it.
>
> Also, this helps making clear that here the lock is only protecting the
> counter.
While moving the flag clearing is ok I am wondering why do we need that
in the first place. I think it is just a leftover from 6c0371490140
("hugetlb: convert PageHugeFreed to HPageFreed flag"). Prior to that a tail
page as been used to keep track of the state but now all happens in the
head page and the flag uses page->private which is always initialized
when allocated by the allocator (post_alloc_hook).
Or do we need it for giga pages which are not allocated by the page
allocator? If yes then moving it to prep_compound_gigantic_page would be
better.
So should we just drop it here?
> Signed-off-by: Oscar Salvador <osalva...@suse.de>
> ---
> mm/hugetlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 54d81d5947ed..e40d5fe5c63c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1490,10 +1490,10 @@ static void prep_new_huge_page(struct hstate *h,
> struct page *page, int nid)
> hugetlb_set_page_subpool(page, NULL);
> set_hugetlb_cgroup(page, NULL);
> set_hugetlb_cgroup_rsvd(page, NULL);
> + ClearHPageFreed(page);
> spin_lock_irq(&hugetlb_lock);
> h->nr_huge_pages++;
> h->nr_huge_pages_node[nid]++;
> - ClearHPageFreed(page);
> spin_unlock_irq(&hugetlb_lock);
> }
>
> --
> 2.16.3
--
Michal Hocko
SUSE Labs
