[PATCH v2 49/69] mm/hugetlb_vmemmap: Remove vmemmap_wrprotect_hvo()

[Muchun Song]

Shared vmemmap tail pages are now mapped read-only when their PTEs are
installed, so HugeTLB bootmem optimization no longer needs a separate
write-protect pass afterwards.

Remove vmemmap_wrprotect_hvo() and the bootmem-specific HugeTLB wrapper,
and let bootmem folios use the normal hugetlb_vmemmap_optimize_folios()
path.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/linux/mm.h   |  2 --
 mm/hugetlb.c         |  2 +-
 mm/hugetlb_vmemmap.c | 45 +++++++++-----------------------------------
 mm/hugetlb_vmemmap.h |  6 ------
 mm/sparse-vmemmap.c  | 23 ----------------------
 5 files changed, 10 insertions(+), 68 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 86d7cecb834e..5e38c9a16a0a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4863,8 +4863,6 @@ 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);
 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 74770c1648fc..54ef7d12c585 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3202,7 +3202,7 @@ 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 d24143dd6051..fce772e95adc 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -595,31 +595,22 @@ 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 + hugetlb_vmemmap_size(h);
-			vmemmap_wrprotect_hvo(spfn, epfn, folio_nid(folio),
-					OPTIMIZED_FOLIO_VMEMMAP_SIZE);
+
+		/*
+		 * Bootmem gigantic folios may already be marked optimized when
+		 * their vmemmap layout was prepared earlier, so skip them here.
+		 */
+		if (folio_test_hugetlb_vmemmap_optimized(folio))
 			continue;
-		}
 
 		nr_to_optimize++;
 
@@ -636,14 +627,7 @@ static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,
 	}
 
 	if (!nr_to_optimize)
-		/*
-		 * All pre-HVO folios, nothing left to do. It's ok if
-		 * there is a mix of pre-HVO and not yet HVO-ed folios
-		 * here, as __hugetlb_vmemmap_optimize_folio() will
-		 * skip any folios that already have the optimized flag
-		 * set, see vmemmap_should_optimize_folio().
-		 */
-		goto out;
+		return;
 
 	flush_tlb_all();
 
@@ -668,21 +652,10 @@ static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,
 		}
 	}
 
-out:
 	flush_tlb_all();
 	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 0d8c88997066..2b0a85e09602 100644
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h
@@ -17,7 +17,6 @@ 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)
@@ -59,11 +58,6 @@ 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 5d5cd5f73365..ce1cf5cdf613 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -265,29 +265,6 @@ 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 __ref *vmemmap_shared_tail_page(unsigned int order, struct zone *zone)
 {
 	void *addr;
-- 
2.54.0