[PATCH 3/4] mm/hugetlb_vmemmap: remove vmemmap_wrprotect_hvo()

[Muchun Song]

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.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/linux/mm.h   |  2 --
 mm/hugetlb_vmemmap.c | 18 ++++++------------
 mm/sparse-vmemmap.c  | 23 -----------------------
 3 files changed, 6 insertions(+), 37 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 35f5fc43861a..6f5affe54946 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5359,8 +5359,6 @@ int vmemmap_populate_hugepages(unsigned long start, unsigned long end,
 			       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,
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 0057fa2a16a8..3d72346c2ca2 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -603,19 +603,13 @@ static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,
 	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++;
 
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index ba0496daf4de..0af4b9e791b2 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -386,29 +386,6 @@ 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);
-	}
-}
-
 void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
 				      unsigned long addr, unsigned long next)
 {
-- 
2.54.0