target: use offset_in_page macro

Use offset_in_page macro instead of (addr & ~PAGE_MASK).

Signed-off-by: Geliang Tang <geliangtang@163.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 937cebf..d5477c0 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -194,7 +194,7 @@
 
 static inline void tcmu_flush_dcache_range(void *vaddr, size_t size)
 {
-	unsigned long offset = (unsigned long) vaddr & ~PAGE_MASK;
+	unsigned long offset = offset_in_page(vaddr);
 
 	size = round_up(size+offset, PAGE_SIZE);
 	vaddr -= offset;