The patch titled
Subject: mm: page_owner: use new iteration API
has been added to the -mm mm-unstable branch. Its filename is
mm-page_owner-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_owner-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_owner: use new iteration API
Date: Mon, 24 Feb 2025 16:59:08 -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/badc717329c288c58b7abf7513603aa3042c008c.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_owner.c | 61 +++++++++++++++++++++-------------------------
1 file changed, 29 insertions(+), 32 deletions(-)
--- a/mm/page_owner.c~mm-page_owner-use-new-iteration-api
+++ a/mm/page_owner.c
@@ -229,17 +229,19 @@ static void dec_stack_record_count(depot
handle);
}
-static inline void __update_page_owner_handle(struct page_ext *page_ext,
+static inline void __update_page_owner_handle(struct page *page,
depot_stack_handle_t handle,
unsigned short order,
gfp_t gfp_mask,
short last_migrate_reason, u64 ts_nsec,
pid_t pid, pid_t tgid, char *comm)
{
- int i;
+ struct page_ext_iter iter;
+ struct page_ext *page_ext;
struct page_owner *page_owner;
- for (i = 0; i < (1 << order); i++) {
+ rcu_read_lock();
+ for_each_page_ext(page, 1 << order, page_ext, iter) {
page_owner = get_page_owner(page_ext);
page_owner->handle = handle;
page_owner->order = order;
@@ -252,20 +254,22 @@ static inline void __update_page_owner_h
sizeof(page_owner->comm));
__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
- page_ext = page_ext_next(page_ext);
}
+ rcu_read_unlock();
}
-static inline void __update_page_owner_free_handle(struct page_ext *page_ext,
+static inline void __update_page_owner_free_handle(struct page *page,
depot_stack_handle_t handle,
unsigned short order,
pid_t pid, pid_t tgid,
u64 free_ts_nsec)
{
- int i;
+ struct page_ext_iter iter;
+ struct page_ext *page_ext;
struct page_owner *page_owner;
- for (i = 0; i < (1 << order); i++) {
+ rcu_read_lock();
+ for_each_page_ext(page, 1 << order, page_ext, iter) {
page_owner = get_page_owner(page_ext);
/* Only __reset_page_owner() wants to clear the bit */
if (handle) {
@@ -275,8 +279,8 @@ static inline void __update_page_owner_f
page_owner->free_ts_nsec = free_ts_nsec;
page_owner->free_pid = current->pid;
page_owner->free_tgid = current->tgid;
- page_ext = page_ext_next(page_ext);
}
+ rcu_read_unlock();
}
void __reset_page_owner(struct page *page, unsigned short order)
@@ -293,11 +297,11 @@ void __reset_page_owner(struct page *pag
page_owner = get_page_owner(page_ext);
alloc_handle = page_owner->handle;
+ page_ext_put(page_ext);
handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
- __update_page_owner_free_handle(page_ext, handle, order, current->pid,
+ __update_page_owner_free_handle(page, handle, order, current->pid,
current->tgid, free_ts_nsec);
- page_ext_put(page_ext);
if (alloc_handle != early_handle)
/*
@@ -313,19 +317,13 @@ void __reset_page_owner(struct page *pag
noinline void __set_page_owner(struct page *page, unsigned short order,
gfp_t gfp_mask)
{
- struct page_ext *page_ext;
u64 ts_nsec = local_clock();
depot_stack_handle_t handle;
handle = save_stack(gfp_mask);
-
- page_ext = page_ext_get(page);
- if (unlikely(!page_ext))
- return;
- __update_page_owner_handle(page_ext, handle, order, gfp_mask, -1,
+ __update_page_owner_handle(page, handle, order, gfp_mask, -1,
ts_nsec, current->pid, current->tgid,
current->comm);
- page_ext_put(page_ext);
inc_stack_record_count(handle, gfp_mask, 1 << order);
}
@@ -344,26 +342,24 @@ void __set_page_owner_migrate_reason(str
void __split_page_owner(struct page *page, int old_order, int new_order)
{
- int i;
- struct page_ext *page_ext = page_ext_get(page);
+ struct page_ext_iter iter;
+ struct page_ext *page_ext;
struct page_owner *page_owner;
- if (unlikely(!page_ext))
- return;
-
- for (i = 0; i < (1 << old_order); i++) {
+ rcu_read_lock();
+ for_each_page_ext(page, 1 << old_order, page_ext, iter) {
page_owner = get_page_owner(page_ext);
page_owner->order = new_order;
- page_ext = page_ext_next(page_ext);
}
- page_ext_put(page_ext);
+ rcu_read_unlock();
}
void __folio_copy_owner(struct folio *newfolio, struct folio *old)
{
- int i;
struct page_ext *old_ext;
struct page_ext *new_ext;
+ struct page_ext *page_ext;
+ struct page_ext_iter iter;
struct page_owner *old_page_owner;
struct page_owner *new_page_owner;
depot_stack_handle_t migrate_handle;
@@ -381,7 +377,7 @@ void __folio_copy_owner(struct folio *ne
old_page_owner = get_page_owner(old_ext);
new_page_owner = get_page_owner(new_ext);
migrate_handle = new_page_owner->handle;
- __update_page_owner_handle(new_ext, old_page_owner->handle,
+ __update_page_owner_handle(&newfolio->page, old_page_owner->handle,
old_page_owner->order, old_page_owner->gfp_mask,
old_page_owner->last_migrate_reason,
old_page_owner->ts_nsec, old_page_owner->pid,
@@ -391,7 +387,7 @@ void __folio_copy_owner(struct folio *ne
* will be freed after migration. Keep them until then as they may be
* useful.
*/
- __update_page_owner_free_handle(new_ext, 0, old_page_owner->order,
+ __update_page_owner_free_handle(&newfolio->page, 0, old_page_owner->order,
old_page_owner->free_pid,
old_page_owner->free_tgid,
old_page_owner->free_ts_nsec);
@@ -400,11 +396,12 @@ void __folio_copy_owner(struct folio *ne
* for the new one and the old folio otherwise there will be an imbalance
* when subtracting those pages from the stack.
*/
- for (i = 0; i < (1 << new_page_owner->order); i++) {
+ rcu_read_lock();
+ for_each_page_ext(&old->page, 1 << new_page_owner->order, page_ext, iter) {
+ old_page_owner = get_page_owner(page_ext);
old_page_owner->handle = migrate_handle;
- old_ext = page_ext_next(old_ext);
- old_page_owner = get_page_owner(old_ext);
}
+ rcu_read_unlock();
page_ext_put(new_ext);
page_ext_put(old_ext);
@@ -813,7 +810,7 @@ static void init_pages_in_zone(pg_data_t
goto ext_put_continue;
/* Found early allocated page */
- __update_page_owner_handle(page_ext, early_handle, 0, 0,
+ __update_page_owner_handle(page, early_handle, 0, 0,
-1, local_clock(), current->pid,
current->tgid, current->comm);
count++;
_
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
