From 7216db147f571746e584614ed313892a26cba8ef Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Date: Tue, 4 Jun 2024 12:00:45 -0400
Subject: [PATCH] Revert "mm/madvise: optimize lazyfreeing with mTHP in
 madvise_free"

This reverts commit dce7d10be4bbd31412c4bedd3a8bb2d25b96e025.
---
 mm/madvise.c | 85 +++++++++++++++++++++++++---------------------------
 1 file changed, 41 insertions(+), 44 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index a77893462b92..284abcf07eb4 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -643,7 +643,6 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 				unsigned long end, struct mm_walk *walk)
 
 {
-	const cydp_t cydp_flags = CYDP_CLEAR_YOUNG | CYDP_CLEAR_DIRTY;
 	struct mmu_gather *tlb = walk->private;
 	struct mm_struct *mm = tlb->mm;
 	struct vm_area_struct *vma = walk->vma;
@@ -698,57 +697,44 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 			continue;
 
 		/*
-		 * If we encounter a large folio, only split it if it is not
-		 * fully mapped within the range we are operating on. Otherwise
-		 * leave it as is so that it can be marked as lazyfree. If we
-		 * fail to split a folio, leave it in place and advance to the
-		 * next pte in the range.
+		 * If pmd isn't transhuge but the folio is large and
+		 * is owned by only this process, split it and
+		 * deactivate all pages.
 		 */
 		if (folio_test_large(folio)) {
-			bool any_young, any_dirty;
-
-			nr = madvise_folio_pte_batch(addr, end, folio, pte,
-						     ptent, &any_young, &any_dirty);
-
-			if (nr < folio_nr_pages(folio)) {
-				int err;
-
-				if (folio_likely_mapped_shared(folio))
-					continue;
-				if (!folio_trylock(folio))
-					continue;
-				folio_get(folio);
-				arch_leave_lazy_mmu_mode();
-				pte_unmap_unlock(start_pte, ptl);
-				start_pte = NULL;
-				err = split_folio(folio);
-				folio_unlock(folio);
-				folio_put(folio);
-				pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
-				start_pte = pte;
-				if (!start_pte)
-					break;
-				arch_enter_lazy_mmu_mode();
-				if (!err)
-					nr = 0;
-				continue;
-			}
+			int err;
 
-			if (any_young)
-				ptent = pte_mkyoung(ptent);
-			if (any_dirty)
-				ptent = pte_mkdirty(ptent);
+			if (folio_likely_mapped_shared(folio))
+				break;
+			if (!folio_trylock(folio))
+				break;
+			folio_get(folio);
+			arch_leave_lazy_mmu_mode();
+			pte_unmap_unlock(start_pte, ptl);
+			start_pte = NULL;
+			err = split_folio(folio);
+			folio_unlock(folio);
+			folio_put(folio);
+			if (err)
+				break;
+			start_pte = pte =
+				pte_offset_map_lock(mm, pmd, addr, &ptl);
+			if (!start_pte)
+				break;
+			arch_enter_lazy_mmu_mode();
+			pte--;
+			addr -= PAGE_SIZE;
+			continue;
 		}
 
 		if (folio_test_swapcache(folio) || folio_test_dirty(folio)) {
 			if (!folio_trylock(folio))
 				continue;
 			/*
-			 * If we have a large folio at this point, we know it is
-			 * fully mapped so if its mapcount is the same as its
-			 * number of pages, it must be exclusive.
+			 * If folio is shared with others, we mustn't clear
+			 * the folio's dirty flag.
 			 */
-			if (folio_mapcount(folio) != folio_nr_pages(folio)) {
+			if (folio_mapcount(folio) != 1) {
 				folio_unlock(folio);
 				continue;
 			}
@@ -764,8 +750,19 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 		}
 
 		if (pte_young(ptent) || pte_dirty(ptent)) {
-			clear_young_dirty_ptes(vma, addr, pte, nr, cydp_flags);
-			tlb_remove_tlb_entries(tlb, pte, nr, addr);
+			/*
+			 * Some of architecture(ex, PPC) don't update TLB
+			 * with set_pte_at and tlb_remove_tlb_entry so for
+			 * the portability, remap the pte with old|clean
+			 * after pte clearing.
+			 */
+			ptent = ptep_get_and_clear_full(mm, addr, pte,
+							tlb->fullmm);
+
+			ptent = pte_mkold(ptent);
+			ptent = pte_mkclean(ptent);
+			set_pte_at(mm, addr, pte, ptent);
+			tlb_remove_tlb_entry(tlb, pte, addr);
 		}
 		folio_mark_lazyfree(folio);
 	}
-- 
2.49.0