[PATCH 40/49] mm/hugetlb_vmemmap: remove vmemmap_wrprotect_hvo() and related code

Muchun Song
2026-04-05T12:57:55Z

Since we have already remapped the shared tail pages as read-only in
vmemmap_pte_populate() right at the point of mapping establishment,
the separate pass of read-only mapping enforcement via
vmemmap_wrprotect_hvo() for HugeTLB bootmem folios is no longer
necessary.

Remove vmemmap_wrprotect_hvo() and the associated wrapper
hugetlb_vmemmap_optimize_bootmem_folios(), simplifying the code by
directly using hugetlb_vmemmap_optimize_folios() for bootmem folios
as well.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
include/linux/mm.h | 2 --
mm/hugetlb.c | 2 +-
mm/hugetlb_vmemmap.c | 31 ++++---------------------------
mm/hugetlb_vmemmap.h | 6 ------
mm/sparse-vmemmap.c | 23 -----------------------
5 files changed, 5 insertions(+), 59 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bceef0dc578b..c36001c9d571 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4877,8 +4877,6 @@ int vmemmap_populate_hugepages(unsigned long start, unsigned long end,
struct dev_pagemap *pgmap);
int vmemmap_populate(unsigned long start, unsigned long end, int node,
struct vmem_altmap *altmap, struct dev_pagemap *pgmap);
-void vmemmap_wrprotect_hvo(unsigned long start, unsigned long end, int node,
- unsigned long headsize);
void vmemmap_populate_print_last(void);
struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone);
#ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ce5a58aab5c3..84f095a23ef2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3226,7 +3226,7 @@ static void __init prep_and_add_bootmem_folios(struct hstate *h,
struct folio *folio, *tmp_f;

/* Send list for bulk vmemmap optimization processing */
- hugetlb_vmemmap_optimize_bootmem_folios(h, folio_list);
+ hugetlb_vmemmap_optimize_folios(h, folio_list);

list_for_each_entry_safe(folio, tmp_f, folio_list, lru) {
if (!folio_test_hugetlb_vmemmap_optimized(folio)) {
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 92c95ebdbb9a..d595ef759bc2 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -589,31 +589,18 @@ static int hugetlb_vmemmap_split_folio(const struct hstate *h, struct folio *fol
return vmemmap_remap_split(vmemmap_start, vmemmap_end);
}

-static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,
- struct list_head *folio_list,
- bool boot)
+void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list)
{
struct folio *folio;
- int nr_to_optimize;
+ unsigned long nr_to_optimize = 0;
LIST_HEAD(vmemmap_pages);
unsigned long flags = VMEMMAP_REMAP_NO_TLB_FLUSH;

- nr_to_optimize = 0;
list_for_each_entry(folio, folio_list, lru) {
int ret;
- unsigned long spfn, epfn;
-
- if (boot && folio_test_hugetlb_vmemmap_optimized(folio)) {
- /*
- * Already optimized by pre-HVO, just map the
- * mirrored tail page structs RO.
- */
- spfn = (unsigned long)&folio->page;
- epfn = spfn + pages_per_huge_page(h);
- vmemmap_wrprotect_hvo(spfn, epfn, folio_nid(folio),
- OPTIMIZED_FOLIO_VMEMMAP_SIZE);
+
+ if (folio_test_hugetlb_vmemmap_optimized(folio))
continue;
- }

nr_to_optimize++;

@@ -667,16 +654,6 @@ static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,
free_vmemmap_page_list(&vmemmap_pages);
}

-void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list)
-{
- __hugetlb_vmemmap_optimize_folios(h, folio_list, false);
-}
-
-void hugetlb_vmemmap_optimize_bootmem_folios(struct hstate *h, struct list_head *folio_list)
-{
- __hugetlb_vmemmap_optimize_folios(h, folio_list, true);
-}
-
void __init hugetlb_vmemmap_optimize_bootmem_page(struct huge_bootmem_page *m)
{
struct hstate *h = m->hstate;
diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
index ff8e4c6e9833..0022f9c5a101 100644
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h
@@ -19,7 +19,6 @@ long hugetlb_vmemmap_restore_folios(const struct hstate *h,
struct list_head *non_hvo_folios);
void hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct folio *folio);
void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list);
-void hugetlb_vmemmap_optimize_bootmem_folios(struct hstate *h, struct list_head *folio_list);
void hugetlb_vmemmap_optimize_bootmem_page(struct huge_bootmem_page *m);

static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
@@ -61,11 +60,6 @@ static inline void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list
{
}

-static inline void hugetlb_vmemmap_optimize_bootmem_folios(struct hstate *h,
- struct list_head *folio_list)
-{
-}
-
static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
{
return 0;
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 36e5bcb5ba9b..ba8c0c64f160 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -296,29 +296,6 @@ int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
return 0;
}

-/*
- * Write protect the mirrored tail page structs for HVO. This will be
- * called from the hugetlb code when gathering and initializing the
- * memblock allocated gigantic pages. The write protect can't be
- * done earlier, since it can't be guaranteed that the reserved
- * page structures will not be written to during initialization,
- * even if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
- *
- * The PTEs are known to exist, and nothing else should be touching
- * these pages. The caller is responsible for any TLB flushing.
- */
-void vmemmap_wrprotect_hvo(unsigned long addr, unsigned long end,
- int node, unsigned long headsize)
-{
- unsigned long maddr;
- pte_t *pte;
-
- for (maddr = addr + headsize; maddr < end; maddr += PAGE_SIZE) {
- pte = virt_to_kpte(maddr);
- ptep_set_wrprotect(&init_mm, maddr, pte);
- }
-}
-
struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone)
{
void *addr;
--
2.20.1