filesystem-dax: Do not request kaddr and pfn when not required

Some functions within fs/dax don't need to get local pointer kaddr
or variable pfn from direct_access. Using NULL instead of having to
pass in useless pointer or variable that caller then just throw away.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

fs/dax.c

@@ -647,7 +647,6 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
 {
 	void *vto, *kaddr;
 	pgoff_t pgoff;
-	pfn_t pfn;
 	long rc;
 	int id;
 
@@ -656,7 +655,7 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
 		return rc;
 
 	id = dax_read_lock();
-	rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
+	rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, NULL);
 	if (rc < 0) {
 		dax_read_unlock(id);
 		return rc;
@@ -967,7 +966,6 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 {
 	const sector_t sector = dax_iomap_sector(iomap, pos);
 	pgoff_t pgoff;
-	void *kaddr;
 	int id, rc;
 	long length;
 
@@ -976,7 +974,7 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 		return rc;
 	id = dax_read_lock();
 	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
-				   &kaddr, pfnp);
+				   NULL, pfnp);
 	if (length < 0) {
 		rc = length;
 		goto out;
@@ -1052,15 +1050,13 @@ int __dax_zero_page_range(struct block_device *bdev,
 		pgoff_t pgoff;
 		long rc, id;
 		void *kaddr;
-		pfn_t pfn;
 
 		rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
 		if (rc)
 			return rc;
 
 		id = dax_read_lock();
-		rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
-				&pfn);
+		rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
 		if (rc < 0) {
 			dax_read_unlock(id);
 			return rc;
@@ -1116,7 +1112,6 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		ssize_t map_len;
 		pgoff_t pgoff;
 		void *kaddr;
-		pfn_t pfn;
 
 		if (fatal_signal_pending(current)) {
 			ret = -EINTR;
@@ -1128,7 +1123,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 			break;
 
 		map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
-				&kaddr, &pfn);
+				&kaddr, NULL);
 		if (map_len < 0) {
 			ret = map_len;
 			break;