Revert "mm, thp: Do not make pmd/pud dirty without a reason"

This reverts commit 152e93af.

It was a nice cleanup in theory, but as Nicolai Stange points out, we do
need to make the page dirty for the copy-on-write case even when we
didn't end up making it writable, since the dirty bit is what we use to
check that we've gone through a COW cycle.
Reported-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/huge_memory.c

@@ -474,13 +474,10 @@ static int __init setup_transparent_hugepage(char *str)
 }
 __setup("transparent_hugepage=", setup_transparent_hugepage);
 
-pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma, bool dirty)
+pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 {
-	if (likely(vma->vm_flags & VM_WRITE)) {
+	if (likely(vma->vm_flags & VM_WRITE))
 		pmd = pmd_mkwrite(pmd);
-		if (dirty)
-			pmd = pmd_mkdirty(pmd);
-	}
 	return pmd;
 }
 
@@ -602,7 +599,7 @@ static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
 		}
 
 		entry = mk_huge_pmd(page, vma->vm_page_prot);
-		entry = maybe_pmd_mkwrite(entry, vma, true);
+		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 		page_add_new_anon_rmap(page, vma, haddr, true);
 		mem_cgroup_commit_charge(page, memcg, false, true);
 		lru_cache_add_active_or_unevictable(page, vma);
@@ -744,8 +741,8 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 	if (pfn_t_devmap(pfn))
 		entry = pmd_mkdevmap(entry);
 	if (write) {
-		entry = pmd_mkyoung(entry);
-		entry = maybe_pmd_mkwrite(entry, vma, true);
+		entry = pmd_mkyoung(pmd_mkdirty(entry));
+		entry = maybe_pmd_mkwrite(entry, vma);
 	}
 
 	if (pgtable) {
@@ -791,14 +788,10 @@ int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
-static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma,
-		bool dirty)
+static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 {
-	if (likely(vma->vm_flags & VM_WRITE)) {
+	if (likely(vma->vm_flags & VM_WRITE))
 		pud = pud_mkwrite(pud);
-		if (dirty)
-			pud = pud_mkdirty(pud);
-	}
 	return pud;
 }
 
@@ -814,8 +807,8 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 	if (pfn_t_devmap(pfn))
 		entry = pud_mkdevmap(entry);
 	if (write) {
-		entry = pud_mkyoung(entry);
-		entry = maybe_pud_mkwrite(entry, vma, true);
+		entry = pud_mkyoung(pud_mkdirty(entry));
+		entry = maybe_pud_mkwrite(entry, vma);
 	}
 	set_pud_at(mm, addr, pud, entry);
 	update_mmu_cache_pud(vma, addr, pud);
@@ -1286,7 +1279,7 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
 	if (reuse_swap_page(page, NULL)) {
 		pmd_t entry;
 		entry = pmd_mkyoung(orig_pmd);
-		entry = maybe_pmd_mkwrite(entry, vma, true);
+		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 		if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
 			update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 		ret |= VM_FAULT_WRITE;
@@ -1356,7 +1349,7 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
 	} else {
 		pmd_t entry;
 		entry = mk_huge_pmd(new_page, vma->vm_page_prot);
-		entry = maybe_pmd_mkwrite(entry, vma, true);
+		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 		pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
 		page_add_new_anon_rmap(new_page, vma, haddr, true);
 		mem_cgroup_commit_charge(new_page, memcg, false, true);
@@ -2935,7 +2928,7 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
 	if (pmd_swp_soft_dirty(*pvmw->pmd))
 		pmde = pmd_mksoft_dirty(pmde);
 	if (is_write_migration_entry(entry))
-		pmde = maybe_pmd_mkwrite(pmde, vma, false);
+		pmde = maybe_pmd_mkwrite(pmde, vma);
 
 	flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
 	page_add_anon_rmap(new, vma, mmun_start, true);

mm/internal.h

@@ -328,8 +328,7 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
 	}
 }
 
-extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma,
-		bool dirty);
+extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
 
 /*
  * At what user virtual address is page expected in @vma?

mm/khugepaged.c

@@ -1057,7 +1057,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	pgtable = pmd_pgtable(_pmd);
 
 	_pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
-	_pmd = maybe_pmd_mkwrite(_pmd, vma, false);
+	_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
 
 	/*
 	 * spin_lock() below is not the equivalent of smp_wmb(), so

mm/memory.c

@@ -3335,7 +3335,7 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page)
 
 	entry = mk_huge_pmd(page, vma->vm_page_prot);
 	if (write)
-		entry = maybe_pmd_mkwrite(entry, vma, true);
+		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 
 	add_mm_counter(vma->vm_mm, MM_FILEPAGES, HPAGE_PMD_NR);
 	page_add_file_rmap(page, true);

mm/migrate.c

@@ -2068,7 +2068,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 	}
 
 	entry = mk_huge_pmd(new_page, vma->vm_page_prot);
-	entry = maybe_pmd_mkwrite(entry, vma, false);
+	entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 
 	/*
 	 * Clear the old entry under pagetable lock and establish the new PTE.