[PATCH RFC 12/30] mm: Pass zap_flags into unmap_mapping_pages()

[Peter Xu <peterx@redhat.com>]

Give unmap_mapping_pages() more power by allowing to specify a zap flag so that
it can pass in more information than "whether we'd also like to zap cow pages".
With the new flag, we can remove the even_cow parameter because even_cow==false
equals to zap_flags==ZAP_FLAG_CHECK_MAPPING, while even_cow==true means a none
zap flag to pass in (though in most cases we have had even_cow==false).

No functional change intended.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 fs/dax.c           | 10 ++++++----
 include/linux/mm.h |  4 ++--
 mm/khugepaged.c    |  3 ++-
 mm/memory.c        | 15 ++++++++-------
 mm/truncate.c      | 11 +++++++----
 5 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 5b47834f2e1b..6a123c2bfc59 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -517,7 +517,7 @@ static void *grab_mapping_entry(struct xa_state *xas,
 			xas_unlock_irq(xas);
 			unmap_mapping_pages(mapping,
 					xas->xa_index & ~PG_PMD_COLOUR,
-					PG_PMD_NR, false);
+					PG_PMD_NR, ZAP_FLAG_CHECK_MAPPING);
 			xas_reset(xas);
 			xas_lock_irq(xas);
 		}
@@ -612,7 +612,8 @@ struct page *dax_layout_busy_page_range(struct address_space *mapping,
 	 * guaranteed to either see new references or prevent new
 	 * references from being established.
 	 */
-	unmap_mapping_pages(mapping, start_idx, end_idx - start_idx + 1, 0);
+	unmap_mapping_pages(mapping, start_idx, end_idx - start_idx + 1,
+			    ZAP_FLAG_CHECK_MAPPING);
 
 	xas_lock_irq(&xas);
 	xas_for_each(&xas, entry, end_idx) {
@@ -743,9 +744,10 @@ static void *dax_insert_entry(struct xa_state *xas,
 		/* we are replacing a zero page with block mapping */
 		if (dax_is_pmd_entry(entry))
 			unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
-					PG_PMD_NR, false);
+					PG_PMD_NR, ZAP_FLAG_CHECK_MAPPING);
 		else /* pte entry */
-			unmap_mapping_pages(mapping, index, 1, false);
+			unmap_mapping_pages(mapping, index, 1,
+					    ZAP_FLAG_CHECK_MAPPING);
 	}
 
 	xas_reset(xas);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0b1d04404275..57bb3d680844 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1710,7 +1710,7 @@ extern int fixup_user_fault(struct mm_struct *mm,
 			    unsigned long address, unsigned int fault_flags,
 			    bool *unlocked);
 void unmap_mapping_pages(struct address_space *mapping,
-		pgoff_t start, pgoff_t nr, bool even_cows);
+		pgoff_t start, pgoff_t nr, unsigned long zap_flags);
 void unmap_mapping_range(struct address_space *mapping,
 		loff_t const holebegin, loff_t const holelen, int even_cows);
 #else
@@ -1730,7 +1730,7 @@ static inline int fixup_user_fault(struct mm_struct *mm, unsigned long address,
 	return -EFAULT;
 }
 static inline void unmap_mapping_pages(struct address_space *mapping,
-		pgoff_t start, pgoff_t nr, bool even_cows) { }
+		pgoff_t start, pgoff_t nr, unsigned long zap_flags) { }
 static inline void unmap_mapping_range(struct address_space *mapping,
 		loff_t const holebegin, loff_t const holelen, int even_cows) { }
 #endif
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 20807163a25f..981d7abb09ef 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1817,7 +1817,8 @@ static void collapse_file(struct mm_struct *mm,
 		}
 
 		if (page_mapped(page))
-			unmap_mapping_pages(mapping, index, 1, false);
+			unmap_mapping_pages(mapping, index, 1,
+					    ZAP_FLAG_CHECK_MAPPING);
 
 		xas_lock_irq(&xas);
 		xas_set(&xas, index);
diff --git a/mm/memory.c b/mm/memory.c
index 873b2515e187..afe09fccdee1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3156,7 +3156,10 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
  * @mapping: The address space containing pages to be unmapped.
  * @start: Index of first page to be unmapped.
  * @nr: Number of pages to be unmapped.  0 to unmap to end of file.
- * @even_cows: Whether to unmap even private COWed pages.
+ * @zap_flags: Zap flags for the process.  E.g., when ZAP_FLAG_CHECK_MAPPING is
+ *   passed into it, we will only zap the pages that are in the same mapping
+ *   specified in the @mapping parameter; otherwise we will not check mapping,
+ *   IOW cow pages will be zapped too.
  *
  * Unmap the pages in this address space from any userspace process which
  * has them mmaped.  Generally, you want to remove COWed pages as well when
@@ -3164,17 +3167,14 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
  * cache.
  */
 void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
-		pgoff_t nr, bool even_cows)
+		pgoff_t nr, unsigned long zap_flags)
 {
 	pgoff_t	first_index = start, last_index = start + nr - 1;
 	struct zap_details details = {
 		.zap_mapping = mapping,
-		.zap_flags = ZAP_FLAG_SKIP_SWAP,
+		.zap_flags = zap_flags | ZAP_FLAG_SKIP_SWAP,
 	};
 
-	if (!even_cows)
-		details.zap_flags |= ZAP_FLAG_CHECK_MAPPING;
-
 	if (last_index < first_index)
 		last_index = ULONG_MAX;
 
@@ -3216,7 +3216,8 @@ void unmap_mapping_range(struct address_space *mapping,
 			hlen = ULONG_MAX - hba + 1;
 	}
 
-	unmap_mapping_pages(mapping, hba, hlen, even_cows);
+	unmap_mapping_pages(mapping, hba, hlen, even_cows ?
+			    0 : ZAP_FLAG_CHECK_MAPPING);
 }
 EXPORT_SYMBOL(unmap_mapping_range);
 
diff --git a/mm/truncate.c b/mm/truncate.c
index 960edf5803ca..dac66749e400 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -178,7 +178,8 @@ truncate_cleanup_page(struct address_space *mapping, struct page *page)
 {
 	if (page_mapped(page)) {
 		unsigned int nr = thp_nr_pages(page);
-		unmap_mapping_pages(mapping, page->index, nr, false);
+		unmap_mapping_pages(mapping, page->index, nr,
+				    ZAP_FLAG_CHECK_MAPPING);
 	}
 
 	if (page_has_private(page))
@@ -750,14 +751,15 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 					 * Zap the rest of the file in one hit.
 					 */
 					unmap_mapping_pages(mapping, index,
-						(1 + end - index), false);
+							    (1 + end - index),
+							    ZAP_FLAG_CHECK_MAPPING);
 					did_range_unmap = 1;
 				} else {
 					/*
 					 * Just zap this page
 					 */
 					unmap_mapping_pages(mapping, index,
-								1, false);
+							    1, ZAP_FLAG_CHECK_MAPPING);
 				}
 			}
 			BUG_ON(page_mapped(page));
@@ -783,7 +785,8 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	 * get remapped later.
 	 */
 	if (dax_mapping(mapping)) {
-		unmap_mapping_pages(mapping, start, end - start + 1, false);
+		unmap_mapping_pages(mapping, start, end - start + 1,
+				    ZAP_FLAG_CHECK_MAPPING);
 	}
 out:
 	cleancache_invalidate_inode(mapping);
-- 
2.26.2