[PATCH RFC v2 17/18] mm: add free_frozen_pages_hint and put_page_hint APIs

Michael S. Tsirkin
2026-04-20T12:51:18Z

Add free_frozen_pages_hint(page, order, hints) to free a page
while marking it as pre-zeroed when PGHINT_ZEROED is set.
The PG_zeroed flag is set after __free_pages_prepare so it
survives on the free list.

Add __folio_put_hint(), folio_put_hint(), and put_page_hint()
wrappers for the put_page path.

These APIs are intended for balloon drivers during deflation
when the host has zeroed the pages.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Assisted-by: Claude:claude-opus-4-6
Assisted-by: cursor-agent:GPT-5.4-xhigh
---
include/linux/gfp.h | 2 ++
include/linux/mm.h | 12 ++++++++++++
mm/page_alloc.c | 21 +++++++++++++++------
mm/swap.c | 19 +++++++++++++++++++
4 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 14433a20e60c..b226d5e1930e 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -404,6 +404,8 @@ __meminit void *alloc_pages_exact_nid_noprof(int nid, size_t size, gfp_t gfp_mas
extern void __free_pages(struct page *page, unsigned int order);
extern void free_pages_nolock(struct page *page, unsigned int order);
extern void free_pages(unsigned long addr, unsigned int order);
+void free_frozen_pages_hint(struct page *page, unsigned int order,
+ pghint_t hints);

#define __free_page(page) __free_pages((page), 0)
#define free_page(addr) free_pages((addr), 0)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index abb4963c1f06..f4e28c55e2c9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1640,6 +1640,7 @@ static inline struct folio *virt_to_folio(const void *x)
}

void __folio_put(struct folio *folio);
+void __folio_put_hint(struct folio *folio, pghint_t hints);

void split_page(struct page *page, unsigned int order);
void folio_copy(struct folio *dst, struct folio *src);
@@ -1817,6 +1818,17 @@ static inline void folio_put(struct folio *folio)
__folio_put(folio);
}

+static inline void folio_put_hint(struct folio *folio, pghint_t hints)
+{
+ if (folio_put_testzero(folio))
+ __folio_put_hint(folio, hints);
+}
+
+static inline void put_page_hint(struct page *page, pghint_t hints)
+{
+ folio_put_hint(page_folio(page), hints);
+}
+
/**
* folio_put_refs - Reduce the reference count on a folio.
* @folio: The folio.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a4cfd645599a..f04813db3015 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3000,7 +3000,7 @@ static bool free_frozen_page_commit(struct zone *zone,
* Free a pcp page
*/
static void __free_frozen_pages(struct page *page, unsigned int order,
- fpi_t fpi_flags)
+ fpi_t fpi_flags, pghint_t hints)
{
unsigned long UP_flags;
struct per_cpu_pages *pcp;
@@ -3016,6 +3016,9 @@ static void __free_frozen_pages(struct page *page, unsigned int order,
if (!__free_pages_prepare(page, order, fpi_flags))
return;

+ if (hints & PGHINT_ZEROED)
+ __SetPageZeroed(page);
+
/*
* We only track unmovable, reclaimable and movable on pcp lists.
* Place ISOLATE pages on the isolated list because they are being
@@ -3051,12 +3054,18 @@ static void __free_frozen_pages(struct page *page, unsigned int order,

void free_frozen_pages(struct page *page, unsigned int order)
{
- __free_frozen_pages(page, order, FPI_NONE);
+ __free_frozen_pages(page, order, FPI_NONE, 0);
+}
+
+void free_frozen_pages_hint(struct page *page, unsigned int order,
+ pghint_t hints)
+{
+ __free_frozen_pages(page, order, FPI_NONE, hints);
}

void free_frozen_pages_nolock(struct page *page, unsigned int order)
{
- __free_frozen_pages(page, order, FPI_TRYLOCK);
+ __free_frozen_pages(page, order, FPI_TRYLOCK, 0);
}

/*
@@ -5385,7 +5394,7 @@ static void ___free_pages(struct page *page, unsigned int order,
struct alloc_tag *tag = pgalloc_tag_get(page);

if (put_page_testzero(page))
- __free_frozen_pages(page, order, fpi_flags);
+ __free_frozen_pages(page, order, fpi_flags, 0);
else if (!head) {
pgalloc_tag_sub_pages(tag, (1 << order) - 1);
while (order-- > 0) {
@@ -5396,7 +5405,7 @@ static void ___free_pages(struct page *page, unsigned int order,
*/
clear_page_tag_ref(page + (1 << order));
__free_frozen_pages(page + (1 << order), order,
- fpi_flags);
+ fpi_flags, 0);
}
}
}
@@ -7879,7 +7888,7 @@ struct page *alloc_frozen_pages_nolock_noprof(gfp_t gfp_flags, int nid, unsigned

if (memcg_kmem_online() && page && (gfp_flags & __GFP_ACCOUNT) &&
unlikely(__memcg_kmem_charge_page(page, alloc_gfp, order) != 0)) {
- __free_frozen_pages(page, order, FPI_TRYLOCK);
+ __free_frozen_pages(page, order, FPI_TRYLOCK, 0);
page = NULL;
}
trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);
diff --git a/mm/swap.c b/mm/swap.c
index bb19ccbece46..1dfd232d3944 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -113,6 +113,25 @@ void __folio_put(struct folio *folio)
}
EXPORT_SYMBOL(__folio_put);

+void __folio_put_hint(struct folio *folio, pghint_t hints)
+{
+ if (unlikely(folio_is_zone_device(folio))) {
+ free_zone_device_folio(folio);
+ return;
+ }
+
+ if (folio_test_hugetlb(folio)) {
+ free_huge_folio(folio);
+ return;
+ }
+
+ page_cache_release(folio);
+ folio_unqueue_deferred_split(folio);
+ mem_cgroup_uncharge(folio);
+ free_frozen_pages_hint(&folio->page, folio_order(folio), hints);
+}
+EXPORT_SYMBOL(__folio_put_hint);
+
typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);

static void lru_add(struct lruvec *lruvec, struct folio *folio)
--
MST