[PATCH v2 9/9] mm: hugetlb: allocate frozen pages in alloc_gigantic_folio()

Kefeng Wang
2025-09-02T12:49:36Z

The alloc_gigantic_folio() will allocate a folio by alloc_contig_range()
with refcount increated and then freeze it, convert to allocate a frozen
folio directly to remove the atomic operation about folio refcount, also
saving atomic operation during __update_and_free_hugetlb_folio too.

Rename some functions to make them more self-explanatory,

folio_alloc_gigantic -> folio_alloc_frozen_gigantic
cma_alloc/free_folio -> cma_alloc/free_frozen_folio
hugetlb_cma_alloc/free_folio -> hugetlb_cma_alloc/free_frozen_folio

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
include/linux/cma.h | 8 ++++----
include/linux/gfp.h | 14 ++++++-------
mm/cma.c | 22 +++++++++++++-------
mm/hugetlb.c | 50 +++++++++------------------------------------
mm/hugetlb_cma.c | 13 ++++++------
mm/hugetlb_cma.h | 10 ++++-----
6 files changed, 47 insertions(+), 70 deletions(-)

diff --git a/include/linux/cma.h b/include/linux/cma.h
index e5745d2aec55..cceec7b25bae 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -57,16 +57,16 @@ extern bool cma_intersects(struct cma *cma, unsigned long start, unsigned long e
extern void cma_reserve_pages_on_error(struct cma *cma);

#ifdef CONFIG_CMA
-struct folio *cma_alloc_folio(struct cma *cma, int order, gfp_t gfp);
-bool cma_free_folio(struct cma *cma, const struct folio *folio);
+struct folio *cma_alloc_frozen_folio(struct cma *cma, int order, gfp_t gfp);
+bool cma_free_frozen_folio(struct cma *cma, const struct folio *folio);
bool cma_validate_zones(struct cma *cma);
#else
-static inline struct folio *cma_alloc_folio(struct cma *cma, int order, gfp_t gfp)
+static inline struct folio *cma_alloc_frozen_folio(struct cma *cma, int order, gfp_t gfp)
{
return NULL;
}

-static inline bool cma_free_folio(struct cma *cma, const struct folio *folio)
+static inline bool cma_free_frozen_folio(struct cma *cma, const struct folio *folio)
{
return false;
}
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index d0047b85fe34..ceda042be704 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -447,26 +447,26 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages,
void free_contig_range(unsigned long pfn, unsigned long nr_pages);

#ifdef CONFIG_CONTIG_ALLOC
-static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp,
- int nid, nodemask_t *node)
+static inline struct folio *folio_alloc_frozen_gigantic_noprof(int order,
+ gfp_t gfp, int nid, nodemask_t *node)
{
struct page *page;

if (WARN_ON(!order || !(gfp & __GFP_COMP)))
return NULL;

- page = alloc_contig_pages_noprof(1 << order, gfp, nid, node);
+ page = alloc_contig_frozen_pages_noprof(1 << order, gfp, nid, node);

return page ? page_folio(page) : NULL;
}
#else
-static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp,
- int nid, nodemask_t *node)
+static inline struct folio *folio_alloc_frozen_gigantic_noprof(int order,
+ gfp_t gfp, int nid, nodemask_t *node)
{
return NULL;
}
#endif
-/* This should be paired with folio_put() rather than free_contig_range(). */
-#define folio_alloc_gigantic(...) alloc_hooks(folio_alloc_gigantic_noprof(__VA_ARGS__))
+/* This must be paired with free_frozen_pages() rather than free_contig_range(). */
+#define folio_alloc_frozen_gigantic(...) alloc_hooks(folio_alloc_frozen_gigantic_noprof(__VA_ARGS__))

#endif /* __LINUX_GFP_H */
diff --git a/mm/cma.c b/mm/cma.c
index b4413e382d5d..49d53879c1d0 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -924,20 +924,21 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
ACR_FLAGS_CMA);
}

-struct folio *cma_alloc_folio(struct cma *cma, int order, gfp_t gfp)
+struct folio *cma_alloc_frozen_folio(struct cma *cma, int order, gfp_t gfp)
{
struct page *page;

if (WARN_ON(!order || !(gfp & __GFP_COMP)))
return NULL;

- page = __cma_alloc(cma, 1 << order, order, gfp, ACR_FLAGS_CMA);
+ page = __cma_alloc(cma, 1 << order, order, gfp,
+ ACR_FLAGS_CMA | ACR_FLAGS_FROZEN);

return page ? page_folio(page) : NULL;
}

static bool __cma_release(struct cma *cma, const struct page *pages,
- unsigned long count)
+ unsigned long count, bool frozen_page)
{
unsigned long pfn, end;
int r;
@@ -960,7 +961,14 @@ static bool __cma_release(struct cma *cma, const struct page *pages,
if (r == cma->nranges)
return false;

- free_contig_range(pfn, count);
+ if (frozen_page) {
+ struct page *head_page = compound_head((struct page *)pages);
+
+ free_frozen_pages(head_page, compound_order(head_page));
+ } else {
+ free_contig_range(pfn, count);
+ }
+
cma_clear_bitmap(cma, cmr, pfn, count);
cma_sysfs_account_release_pages(cma, count);
trace_cma_release(cma->name, pfn, pages, count);
@@ -981,15 +989,15 @@ static bool __cma_release(struct cma *cma, const struct page *pages,
bool cma_release(struct cma *cma, const struct page *pages,
unsigned long count)
{
- return __cma_release(cma, pages, count);
+ return __cma_release(cma, pages, count, false);
}

-bool cma_free_folio(struct cma *cma, const struct folio *folio)
+bool cma_free_frozen_folio(struct cma *cma, const struct folio *folio)
{
if (WARN_ON(!folio_test_large(folio)))
return false;

- return __cma_release(cma, &folio->page, folio_nr_pages(folio));
+ return __cma_release(cma, &folio->page, folio_nr_pages(folio), true);
}

int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4e8709d7deee..1d801bf65916 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -125,16 +125,6 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
unsigned long start, unsigned long end, bool take_locks);
static struct resv_map *vma_resv_map(struct vm_area_struct *vma);

-static void hugetlb_free_folio(struct folio *folio)
-{
- if (folio_test_hugetlb_cma(folio)) {
- hugetlb_cma_free_folio(folio);
- return;
- }
-
- folio_put(folio);
-}
-
static inline bool subpool_is_free(struct hugepage_subpool *spool)
{
if (spool->count)
@@ -1472,43 +1462,20 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
nr_nodes--)

#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-#ifdef CONFIG_CONTIG_ALLOC
static struct folio *alloc_gigantic_folio(int order, gfp_t gfp_mask,
int nid, nodemask_t *nodemask)
{
struct folio *folio;
- bool retried = false;
-
-retry:
- folio = hugetlb_cma_alloc_folio(order, gfp_mask, nid, nodemask);
- if (!folio) {
- if (hugetlb_cma_exclusive_alloc())
- return NULL;
-
- folio = folio_alloc_gigantic(order, gfp_mask, nid, nodemask);
- if (!folio)
- return NULL;
- }

- if (folio_ref_freeze(folio, 1))
+ folio = hugetlb_cma_alloc_frozen_folio(order, gfp_mask, nid, nodemask);
+ if (folio)
return folio;

- pr_warn("HugeTLB: unexpected refcount on PFN %lu\n", folio_pfn(folio));
- hugetlb_free_folio(folio);
- if (!retried) {
- retried = true;
- goto retry;
- }
- return NULL;
-}
+ if (hugetlb_cma_exclusive_alloc())
+ return NULL;

-#else /* !CONFIG_CONTIG_ALLOC */
-static struct folio *alloc_gigantic_folio(int order, gfp_t gfp_mask, int nid,
- nodemask_t *nodemask)
-{
- return NULL;
+ return folio_alloc_frozen_gigantic(order, gfp_mask, nid, nodemask);
}
-#endif /* CONFIG_CONTIG_ALLOC */

#else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
static struct folio *alloc_gigantic_folio(int order, gfp_t gfp_mask, int nid,
@@ -1641,9 +1608,12 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
if (unlikely(folio_test_hwpoison(folio)))
folio_clear_hugetlb_hwpoison(folio);

- folio_ref_unfreeze(folio, 1);
+ VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);

- hugetlb_free_folio(folio);
+ if (folio_test_hugetlb_cma(folio))
+ hugetlb_cma_free_frozen_folio(folio);
+ else
+ free_frozen_pages(&folio->page, folio_order(folio));
}

/*
diff --git a/mm/hugetlb_cma.c b/mm/hugetlb_cma.c
index e8e4dc7182d5..24738a1d6098 100644
--- a/mm/hugetlb_cma.c
+++ b/mm/hugetlb_cma.c
@@ -18,29 +18,28 @@ static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
static bool hugetlb_cma_only;
static unsigned long hugetlb_cma_size __initdata;

-void hugetlb_cma_free_folio(struct folio *folio)
+void hugetlb_cma_free_frozen_folio(struct folio *folio)
{
int nid = folio_nid(folio);

- WARN_ON_ONCE(!cma_free_folio(hugetlb_cma[nid], folio));
+ WARN_ON_ONCE(!cma_free_frozen_folio(hugetlb_cma[nid], folio));
}

-
-struct folio *hugetlb_cma_alloc_folio(int order, gfp_t gfp_mask,
- int nid, nodemask_t *nodemask)
+struct folio *hugetlb_cma_alloc_frozen_folio(int order, gfp_t gfp_mask,
+ int nid, nodemask_t *nodemask)
{
int node;
struct folio *folio = NULL;

if (hugetlb_cma[nid])
- folio = cma_alloc_folio(hugetlb_cma[nid], order, gfp_mask);
+ folio = cma_alloc_frozen_folio(hugetlb_cma[nid], order, gfp_mask);

if (!folio && !(gfp_mask & __GFP_THISNODE)) {
for_each_node_mask(node, *nodemask) {
if (node == nid || !hugetlb_cma[node])
continue;

- folio = cma_alloc_folio(hugetlb_cma[node], order, gfp_mask);
+ folio = cma_alloc_frozen_folio(hugetlb_cma[node], order, gfp_mask);
if (folio)
break;
}
diff --git a/mm/hugetlb_cma.h b/mm/hugetlb_cma.h
index 2c2ec8a7e134..71db3544816e 100644
--- a/mm/hugetlb_cma.h
+++ b/mm/hugetlb_cma.h
@@ -3,8 +3,8 @@
#define _LINUX_HUGETLB_CMA_H

#ifdef CONFIG_CMA
-void hugetlb_cma_free_folio(struct folio *folio);
-struct folio *hugetlb_cma_alloc_folio(int order, gfp_t gfp_mask,
+void hugetlb_cma_free_frozen_folio(struct folio *folio);
+struct folio *hugetlb_cma_alloc_frozen_folio(int order, gfp_t gfp_mask,
int nid, nodemask_t *nodemask);
struct huge_bootmem_page *hugetlb_cma_alloc_bootmem(struct hstate *h, int *nid,
bool node_exact);
@@ -14,12 +14,12 @@ unsigned long hugetlb_cma_total_size(void);
void hugetlb_cma_validate_params(void);
bool hugetlb_early_cma(struct hstate *h);
#else
-static inline void hugetlb_cma_free_folio(struct folio *folio)
+static inline void hugetlb_cma_free_frozen_folio(struct folio *folio)
{
}

-static inline struct folio *hugetlb_cma_alloc_folio(int order, gfp_t gfp_mask,
- int nid, nodemask_t *nodemask)
+static inline struct folio *hugetlb_cma_alloc_frozen_folio(int order,
+ gfp_t gfp_mask, int nid, nodemask_t *nodemask)
{
return NULL;
}
--
2.27.0