Re: [RFC 2/8] mm/hugetlb: remove useless set_page_count()
From: Mike Kravetz <hidden>
Date: 2021-10-26 18:46:30
Also in:
linux-m68k, lkml
On 10/26/21 10:38 AM, Pasha Tatashin wrote:
prep_compound_gigantic_page() calls set_page_count(0, p), but it is not needed because page_ref_freeze(p, 1) already sets refcount to 0. Using, set_page_count() is dangerous, because it unconditionally resets refcount from the current value to unrestrained value, and therefore should be minimized. Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Thanks! My bad for not removing the set_page_count when adding the page_ref_freeze. FYI, there have been additional changes to this routine in Andrew's tree. Not really sure if we want/need the VM_BUG_ON_PAGE as that would only check if there was a 'bug' in page_ref_freeze. -- Mike Kravetz
quoted hunk ↗ jump to hunk
--- mm/hugetlb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 95dc7b83381f..7e3996c8b696 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c@@ -1707,7 +1707,7 @@ static bool prep_compound_gigantic_page(struct page *page, unsigned int order) pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n"); goto out_error; } - set_page_count(p, 0); + VM_BUG_ON_PAGE(page_count(p), p); set_compound_head(p, page); } atomic_set(compound_mapcount_ptr(page), -1);