The patch titled
Subject: mm: page_table_check: use new iteration API
has been added to the -mm mm-unstable branch. Its filename is
mm-page_table_check-use-new-iteration-api.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_table_check-use-new-iteration-api.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Luiz Capitulino <luizcap@xxxxxxxxxx>
Subject: mm: page_table_check: use new iteration API
Date: Mon, 24 Feb 2025 16:59:07 -0500
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.
Link: https://lkml.kernel.org/r/30d246e83e73073451dc3d5fe189b733afbefd07.1740434344.git.luizcap@xxxxxxxxxx
Fixes: cf54f310d0d3 ("mm/hugetlb: use __GFP_COMP for gigantic folios")
Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_table_check.c | 39 ++++++++++++---------------------------
1 file changed, 12 insertions(+), 27 deletions(-)
--- a/mm/page_table_check.c~mm-page_table_check-use-new-iteration-api
+++ a/mm/page_table_check.c
@@ -62,24 +62,20 @@ static struct page_table_check *get_page
*/
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(unsig
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();
}
/*
@@ -102,24 +97,20 @@ static void page_table_check_clear(unsig
static void page_table_check_set(unsigned long pfn, unsigned long pgcnt,
bool rw)
{
+ 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) {
@@ -129,9 +120,8 @@ static void page_table_check_set(unsigne
BUG_ON(atomic_read(&ptc->anon_map_count));
BUG_ON(atomic_inc_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(unsigne
*/
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(page, 1 << order, page_ext, iter) {
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)
_
Patches currently in -mm which might be from luizcap@xxxxxxxxxx are
mm-page_ext-make-lookup_page_ext-public.patch
mm-page_ext-add-an-iteration-api-for-page-extensions.patch
mm-page_table_check-use-new-iteration-api.patch
mm-page_owner-use-new-iteration-api.patch
