Re: [PATCH v2 5/6] mm: hugetlb: fix a race between isolating and freeing page
From: Michal Hocko <mhocko@suse.com>
Date: 2021-01-06 17:11:52
Also in:
lkml
On Wed 06-01-21 16:47:38, Muchun Song wrote:
There is a race between isolate_huge_page() and __free_huge_page().
CPU0: CPU1:
if (PageHuge(page))
put_page(page)
__free_huge_page(page)
spin_lock(&hugetlb_lock)
update_and_free_page(page)
set_compound_page_dtor(page,
NULL_COMPOUND_DTOR)
spin_unlock(&hugetlb_lock)
isolate_huge_page(page)
// trigger BUG_ON
VM_BUG_ON_PAGE(!PageHead(page), page)
spin_lock(&hugetlb_lock)
page_huge_active(page)
// trigger BUG_ON
VM_BUG_ON_PAGE(!PageHuge(page), page)
spin_unlock(&hugetlb_lock)
When we isolate a HugeTLB page on CPU0. Meanwhile, we free it to the
buddy allocator on CPU1. Then, we can trigger a BUG_ON on CPU0. Because
it is already freed to the buddy allocator.
Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Signed-off-by: Muchun Song <redacted>
Reviewed-by: Mike Kravetz <redacted>Acked-by: Michal Hocko <mhocko@suse.com> Thanks!
quoted hunk ↗ jump to hunk
--- mm/hugetlb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bf02e81e3953..67200dd25b1d 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c@@ -5587,9 +5587,9 @@ bool isolate_huge_page(struct page *page, struct list_head *list) { bool ret = true; - VM_BUG_ON_PAGE(!PageHead(page), page); spin_lock(&hugetlb_lock); - if (!page_huge_active(page) || !get_page_unless_zero(page)) { + if (!PageHeadHuge(page) || !page_huge_active(page) || + !get_page_unless_zero(page)) { ret = false; goto unlock; }-- 2.11.0
-- Michal Hocko SUSE Labs