mm: add unmap_mapping_pages()

Several users of unmap_mapping_range() would prefer to express their
range in pages rather than bytes.  Unfortuately, on a 32-bit kernel, you
have to remember to cast your page number to a 64-bit type before
shifting it, and four places in the current tree didn't remember to do
that.  That's a sign of a bad interface.

Conveniently, unmap_mapping_range() actually converts from bytes into
pages, so hoist the guts of unmap_mapping_range() into a new function
unmap_mapping_pages() and convert the callers which want to use pages.

Link: http://lkml.kernel.org/r/20171206142627.GD32044@bombadil.infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reported-by: "zhangyi (F)" <yi.zhang@huawei.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 39 insertions, 37 deletions

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index ea4ff259b671..1cd18e4347fe 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1399,8 +1399,7 @@ static void collapse_shmem(struct mm_struct *mm,
 		}
 
 		if (page_mapped(page))
-			unmap_mapping_range(mapping, index << PAGE_SHIFT,
-					PAGE_SIZE, 0);
+			unmap_mapping_pages(mapping, index, 1, false);
 
 		spin_lock_irq(&mapping->tree_lock);
 
diff --git a/mm/memory.c b/mm/memory.c
index 82a0577933aa..a6e5d6ac5d24 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2799,8 +2799,37 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
 }
 
 /**
+ * unmap_mapping_pages() - Unmap pages from processes.
+ * @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.
+ *
+ * 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
+ * a file is being truncated, but not when invalidating pages from the page
+ * cache.
+ */
+void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
+		pgoff_t nr, bool even_cows)
+{
+	struct zap_details details = { };
+
+	details.check_mapping = even_cows ? NULL : mapping;
+	details.first_index = start;
+	details.last_index = start + nr - 1;
+	if (details.last_index < details.first_index)
+		details.last_index = ULONG_MAX;
+
+	i_mmap_lock_write(mapping);
+	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
+		unmap_mapping_range_tree(&mapping->i_mmap, &details);
+	i_mmap_unlock_write(mapping);
+}
+
+/**
  * unmap_mapping_range - unmap the portion of all mmaps in the specified
- * address_space corresponding to the specified page range in the underlying
+ * address_space corresponding to the specified byte range in the underlying
  * file.
  *
  * @mapping: the address space containing mmaps to be unmapped.
@@ -2818,7 +2847,6 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
 void unmap_mapping_range(struct address_space *mapping,
 		loff_t const holebegin, loff_t const holelen, int even_cows)
 {
-	struct zap_details details = { };
 	pgoff_t hba = holebegin >> PAGE_SHIFT;
 	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
 
@@ -2830,16 +2858,7 @@ void unmap_mapping_range(struct address_space *mapping,
 			hlen = ULONG_MAX - hba + 1;
 	}
 
-	details.check_mapping = even_cows ? NULL : mapping;
-	details.first_index = hba;
-	details.last_index = hba + hlen - 1;
-	if (details.last_index < details.first_index)
-		details.last_index = ULONG_MAX;
-
-	i_mmap_lock_write(mapping);
-	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
-		unmap_mapping_range_tree(&mapping->i_mmap, &details);
-	i_mmap_unlock_write(mapping);
+	unmap_mapping_pages(mapping, hba, hlen, even_cows);
 }
 EXPORT_SYMBOL(unmap_mapping_range);
 
diff --git a/mm/nommu.c b/mm/nommu.c
index 17c00d93de2e..4b9864b17cb0 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1788,13 +1788,6 @@ unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
 	return -ENOMEM;
 }
 
-void unmap_mapping_range(struct address_space *mapping,
-			 loff_t const holebegin, loff_t const holelen,
-			 int even_cows)
-{
-}
-EXPORT_SYMBOL(unmap_mapping_range);
-
 int filemap_fault(struct vm_fault *vmf)
 {
 	BUG();
diff --git a/mm/truncate.c b/mm/truncate.c
index e4b4cf0f4070..c34e2fd4f583 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -179,12 +179,8 @@ static void
 truncate_cleanup_page(struct address_space *mapping, struct page *page)
 {
 	if (page_mapped(page)) {
-		loff_t holelen;
-
-		holelen = PageTransHuge(page) ? HPAGE_PMD_SIZE : PAGE_SIZE;
-		unmap_mapping_range(mapping,
-				   (loff_t)page->index << PAGE_SHIFT,
-				   holelen, 0);
+		pgoff_t nr = PageTransHuge(page) ? HPAGE_PMD_NR : 1;
+		unmap_mapping_pages(mapping, page->index, nr, false);
 	}
 
 	if (page_has_private(page))
@@ -715,19 +711,15 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 					/*
 					 * Zap the rest of the file in one hit.
 					 */
-					unmap_mapping_range(mapping,
-					   (loff_t)index << PAGE_SHIFT,
-					   (loff_t)(1 + end - index)
-							 << PAGE_SHIFT,
-							 0);
+					unmap_mapping_pages(mapping, index,
+						(1 + end - index), false);
 					did_range_unmap = 1;
 				} else {
 					/*
 					 * Just zap this page
 					 */
-					unmap_mapping_range(mapping,
-					   (loff_t)index << PAGE_SHIFT,
-					   PAGE_SIZE, 0);
+					unmap_mapping_pages(mapping, index,
+								1, false);
 				}
 			}
 			BUG_ON(page_mapped(page));
@@ -753,8 +745,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	 * get remapped later.
 	 */
 	if (dax_mapping(mapping)) {
-		unmap_mapping_range(mapping, (loff_t)start << PAGE_SHIFT,
-				    (loff_t)(end - start + 1) << PAGE_SHIFT, 0);
+		unmap_mapping_pages(mapping, start, end - start + 1, false);
 	}
 out:
 	cleancache_invalidate_inode(mapping);