On 2025-02-20 06:05, David Hildenbrand wrote:
On 19.02.25 03:17, Luiz Capitulino wrote:
The page_ext_next() function assumes that page extension objects for a
page order allocation always reside in the same memory section, which
may not be true and could lead to crashes. Use the new page_ext
iteration API instead.
Fixes: cf54f310d0d3 ("mm/hugetlb: use __GFP_COMP for gigantic folios")
Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
---
mm/page_table_check.c | 39 ++++++++++++---------------------------
1 file changed, 12 insertions(+), 27 deletions(-)
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 509c6ef8de400..b52e04d31c809 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -62,24 +62,20 @@ static struct page_table_check *get_page_table_check(struct page_ext *page_ext)
*/
static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt)
{
+ struct page_ext_iter iter;
struct page_ext *page_ext;
struct page *page;
- unsigned long i;
bool anon;
if (!pfn_valid(pfn))
return;
page = pfn_to_page(pfn);
- page_ext = page_ext_get(page);
-
- if (!page_ext)
- return;
-
BUG_ON(PageSlab(page));
anon = PageAnon(page);
- for (i = 0; i < pgcnt; i++) {
+ rcu_read_lock();
+ for_each_page_ext(page, pgcnt, page_ext, iter) {
struct page_table_check *ptc = get_page_table_check(page_ext);
if (anon) {
@@ -89,9 +85,8 @@ static void page_table_check_clear(unsigned long pfn, unsigned long pgcnt)
BUG_ON(atomic_read(&ptc->anon_map_count));
BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0);
}
- page_ext = page_ext_next(page_ext);
}
- page_ext_put(page_ext);
+ rcu_read_unlock();
}
[...]
/*
@@ -140,24 +130,19 @@ static void page_table_check_set(unsigned long pfn, unsigned long pgcnt,
*/
void __page_table_check_zero(struct page *page, unsigned int order)
{
+ struct page_ext_iter iter;
struct page_ext *page_ext;
- unsigned long i;
BUG_ON(PageSlab(page));
- page_ext = page_ext_get(page);
-
- if (!page_ext)
- return;
-
- for (i = 0; i < (1ul << order); i++) {
+ rcu_read_lock();
+ for_each_page_ext_order(page, order, page_ext, iter) {
I would avoid introducing for_each_page_ext_order() and just pass "1 << order" as the page count.
OK, I'll drop it.
struct page_table_check *ptc = get_page_table_check(page_ext);
BUG_ON(atomic_read(&ptc->anon_map_count));
BUG_ON(atomic_read(&ptc->file_map_count));
- page_ext = page_ext_next(page_ext);
}
- page_ext_put(page_ext);
+ rcu_read_unlock();
}
void __page_table_check_pte_clear(struct mm_struct *mm, pte_t pte)
Apart from that, this looks very nice to me
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
