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>

1 files changed, 6 insertions, 13 deletions

diff --git a/fs/dax.c b/fs/dax.c
index c2ebf10b70da..6ee6f7e24f5a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -44,6 +44,7 @@
 
 /* The 'colour' (ie low bits) within a PMD of a page offset.  */
 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
+#define PG_PMD_NR       (PMD_SIZE >> PAGE_SHIFT)
 
 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
@@ -375,8 +376,8 @@ restart:
                  * unmapped.
                  */
                 if (pmd_downgrade && dax_is_zero_entry(entry))
-                        unmap_mapping_range(mapping,
-                                (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+                        unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
+                                                        PG_PMD_NR, false);
 
                 err = radix_tree_preload(
                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
@@ -538,12 +539,10 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
         if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
                 /* we are replacing a zero page with block mapping */
                 if (dax_is_pmd_entry(entry))
-                        unmap_mapping_range(mapping,
-                                        (vmf->pgoff << PAGE_SHIFT) & PMD_MASK,
-                                        PMD_SIZE, 0);
+                        unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
+                                                        PG_PMD_NR, false);
                 else /* pte entry */
-                        unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
-                                        PAGE_SIZE, 0);
+                        unmap_mapping_pages(mapping, vmf->pgoff, 1, false);
         }
 
         spin_lock_irq(&mapping->tree_lock);
@@ -1269,12 +1268,6 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 }
 
 #ifdef CONFIG_FS_DAX_PMD
-/*
- * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
- * more often than one might expect in the below functions.
- */
-#define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
-
 static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
                 void *entry)
 {