mm/munlock: rmap call mlock_vma_page() munlock_vma_page()

Add vma argument to mlock_vma_page() and munlock_vma_page(), make them
inline functions which check (vma->vm_flags & VM_LOCKED) before calling
mlock_page() and munlock_page() in mm/mlock.c.

Add bool compound to mlock_vma_page() and munlock_vma_page(): this is
because we have understandable difficulty in accounting pte maps of THPs,
and if passed a PageHead page, mlock_page() and munlock_page() cannot
tell whether it's a pmd map to be counted or a pte map to be ignored.

Add vma arg to page_add_file_rmap() and page_remove_rmap(), like the
others, and use that to call mlock_vma_page() at the end of the page
adds, and munlock_vma_page() at the end of page_remove_rmap() (end or
beginning? unimportant, but end was easier for assertions in testing).

No page lock is required (although almost all adds happen to hold it):
delete the "Serialize with page migration" BUG_ON(!PageLocked(page))s.
Certainly page lock did serialize with page migration, but I'm having
difficulty explaining why that was ever important.

Mlock accounting on THPs has been hard to define, differed between anon
and file, involved PageDoubleMap in some places and not others, required
clear_page_mlock() at some points.  Keep it simple now: just count the
pmds and ignore the ptes, there is no reason for ptes to undo pmd mlocks.

page_add_new_anon_rmap() callers unchanged: they have long been calling
lru_cache_add_inactive_or_unevictable(), which does its own VM_LOCKED
handling (it also checks for not VM_SPECIAL: I think that's overcautious,
and inconsistent with other checks, that mmap_region() already prevents
VM_LOCKED on VM_SPECIAL; but haven't quite convinced myself to change it).

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

1 files changed, 15 insertions, 30 deletions

diff --git a/mm/memory.c b/mm/memory.c
index c125c4969913..53bd9e5f2e33 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -735,9 +735,6 @@ static void restore_exclusive_pte(struct vm_area_struct *vma,
 
 	set_pte_at(vma->vm_mm, address, ptep, pte);
 
-	if (vma->vm_flags & VM_LOCKED)
-		mlock_vma_page(page);
-
 	/*
 	 * No need to invalidate - it was non-present before. However
 	 * secondary CPUs may have mappings that need invalidating.
@@ -1377,7 +1374,7 @@ again:
 					mark_page_accessed(page);
 			}
 			rss[mm_counter(page)]--;
-			page_remove_rmap(page, false);
+			page_remove_rmap(page, vma, false);
 			if (unlikely(page_mapcount(page) < 0))
 				print_bad_pte(vma, addr, ptent, page);
 			if (unlikely(__tlb_remove_page(tlb, page))) {
@@ -1397,10 +1394,8 @@ again:
 				continue;
 			pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 			rss[mm_counter(page)]--;
-
 			if (is_device_private_entry(entry))
-				page_remove_rmap(page, false);
-
+				page_remove_rmap(page, vma, false);
 			put_page(page);
 			continue;
 		}
@@ -1753,16 +1748,16 @@ static int validate_page_before_insert(struct page *page)
 	return 0;
 }
 
-static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
+static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
 			unsigned long addr, struct page *page, pgprot_t prot)
 {
 	if (!pte_none(*pte))
 		return -EBUSY;
 	/* Ok, finally just insert the thing.. */
 	get_page(page);
-	inc_mm_counter_fast(mm, mm_counter_file(page));
-	page_add_file_rmap(page, false);
-	set_pte_at(mm, addr, pte, mk_pte(page, prot));
+	inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
+	page_add_file_rmap(page, vma, false);
+	set_pte_at(vma->vm_mm, addr, pte, mk_pte(page, prot));
 	return 0;
 }
 
@@ -1776,7 +1771,6 @@ static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 			struct page *page, pgprot_t prot)
 {
-	struct mm_struct *mm = vma->vm_mm;
 	int retval;
 	pte_t *pte;
 	spinlock_t *ptl;
@@ -1785,17 +1779,17 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 	if (retval)
 		goto out;
 	retval = -ENOMEM;
-	pte = get_locked_pte(mm, addr, &ptl);
+	pte = get_locked_pte(vma->vm_mm, addr, &ptl);
 	if (!pte)
 		goto out;
-	retval = insert_page_into_pte_locked(mm, pte, addr, page, prot);
+	retval = insert_page_into_pte_locked(vma, pte, addr, page, prot);
 	pte_unmap_unlock(pte, ptl);
 out:
 	return retval;
 }
 
 #ifdef pte_index
-static int insert_page_in_batch_locked(struct mm_struct *mm, pte_t *pte,
+static int insert_page_in_batch_locked(struct vm_area_struct *vma, pte_t *pte,
 			unsigned long addr, struct page *page, pgprot_t prot)
 {
 	int err;
@@ -1805,7 +1799,7 @@ static int insert_page_in_batch_locked(struct mm_struct *mm, pte_t *pte,
 	err = validate_page_before_insert(page);
 	if (err)
 		return err;
-	return insert_page_into_pte_locked(mm, pte, addr, page, prot);
+	return insert_page_into_pte_locked(vma, pte, addr, page, prot);
 }
 
 /* insert_pages() amortizes the cost of spinlock operations
@@ -1842,7 +1836,7 @@ more:
 
 		start_pte = pte_offset_map_lock(mm, pmd, addr, &pte_lock);
 		for (pte = start_pte; pte_idx < batch_size; ++pte, ++pte_idx) {
-			int err = insert_page_in_batch_locked(mm, pte,
+			int err = insert_page_in_batch_locked(vma, pte,
 				addr, pages[curr_page_idx], prot);
 			if (unlikely(err)) {
 				pte_unmap_unlock(start_pte, pte_lock);
@@ -3098,7 +3092,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 			 * mapcount is visible. So transitively, TLBs to
 			 * old page will be flushed before it can be reused.
 			 */
-			page_remove_rmap(old_page, false);
+			page_remove_rmap(old_page, vma, false);
 		}
 
 		/* Free the old page.. */
@@ -3118,16 +3112,6 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 	 */
 	mmu_notifier_invalidate_range_only_end(&range);
 	if (old_page) {
-		/*
-		 * Don't let another task, with possibly unlocked vma,
-		 * keep the mlocked page.
-		 */
-		if (page_copied && (vma->vm_flags & VM_LOCKED)) {
-			lock_page(old_page);	/* LRU manipulation */
-			if (PageMlocked(old_page))
-				munlock_vma_page(old_page);
-			unlock_page(old_page);
-		}
 		if (page_copied)
 			free_swap_cache(old_page);
 		put_page(old_page);
@@ -3947,7 +3931,8 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 
 	add_mm_counter(vma->vm_mm, mm_counter_file(page), HPAGE_PMD_NR);
-	page_add_file_rmap(page, true);
+	page_add_file_rmap(page, vma, true);
+
 	/*
 	 * deposit and withdraw with pmd lock held
 	 */
@@ -3996,7 +3981,7 @@ void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
 		lru_cache_add_inactive_or_unevictable(page, vma);
 	} else {
 		inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
-		page_add_file_rmap(page, false);
+		page_add_file_rmap(page, vma, false);
 	}
 	set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
 }