+ mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/hugetlb_vmemmap: remove vmemmap_wrprotect_hvo()
has been added to the -mm mm-new branch.  Its filename is
     mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Muchun Song <muchun.song@linux.dev>
Subject: mm/hugetlb_vmemmap: remove vmemmap_wrprotect_hvo()
Date: Mon, 19 Oct 2026 17:08:29 +0800

Shared vmemmap tail pages are now mapped read-only during initial
population, so already optimized HugeTLB bootmem folios no longer need a
separate write-protection pass.

Remove vmemmap_wrprotect_hvo() and skip these folios during boot-time
optimization.

Link: https://lore.kernel.org/20261019090830.1917657-4-songmuchun@bytedance.com
Signed-off-by: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <chleroy@kernel.org>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Qi Zheng <qi.zheng@linux.dev>
---

 include/linux/mm.h   |    2 --
 mm/hugetlb_vmemmap.c |   16 +++++-----------
 mm/sparse-vmemmap.c  |   23 -----------------------
 3 files changed, 5 insertions(+), 36 deletions(-)

--- a/include/linux/mm.h~mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo
+++ a/include/linux/mm.h
@@ -5363,8 +5363,6 @@ int vmemmap_populate_hugepages(unsigned
 			       int node, struct vmem_altmap *altmap);
 int vmemmap_populate(unsigned long start, unsigned long end, int node,
 		struct vmem_altmap *altmap);
-void vmemmap_wrprotect_hvo(unsigned long start, unsigned long end, int node,
-			  unsigned long headsize);
 void vmemmap_populate_print_last(void);
 #ifdef CONFIG_MEMORY_HOTPLUG
 void vmemmap_free(unsigned long start, unsigned long end,
--- a/mm/hugetlb_vmemmap.c~mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo
+++ a/mm/hugetlb_vmemmap.c
@@ -605,19 +605,13 @@ static void __hugetlb_vmemmap_optimize_f
 	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 + hugetlb_vmemmap_size(h);
-			vmemmap_wrprotect_hvo(spfn, epfn, folio_nid(folio),
-					HUGETLB_VMEMMAP_RESERVE_SIZE);
+		/*
+		 * Bootmem gigantic folios may already be marked optimized when
+		 * their vmemmap layout was prepared earlier, so skip them here.
+		 */
+		if (boot && folio_test_hugetlb_vmemmap_optimized(folio))
 			continue;
-		}
 
 		nr_to_optimize++;
 
--- a/mm/sparse-vmemmap.c~mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo
+++ a/mm/sparse-vmemmap.c
@@ -386,29 +386,6 @@ int __meminit vmemmap_populate_basepages
 	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);
-	}
-}
-
 void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
 				      unsigned long addr, unsigned long next)
 {
_

Patches currently in -mm which might be from muchun.song@linux.dev are

riscv-mm-fix-hotplug-page-table-destructor-handling.patch
riscv-mm-fix-missing-destructor-for-hotplug-pud-tables.patch
mm-fix-missing-page-table-destructor-in-pagetable_free.patch
arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch
mm-sparse-vmemmap-map-shared-vmemmap-tail-pages-as-read-only.patch
powerpc-mm-map-shared-vmemmap-tail-pages-as-read-only.patch
mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo.patch
mm-hugetlb_vmemmap-remove-hugetlb_vmemmap_optimize_bootmem_folios.patch