diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index b691b89..726d437 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2061,7 +2061,7 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
 			struct page **pagep, void **fsdata)
 {
 	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
-	loff_t offset = pos & (PAGE_CACHE_SIZE - 1);
+	loff_t offset_of_page_start = pos & PAGE_MASK;
 
 	cFYI(1, ("write_begin from %lld len %d", (long long)pos, len));
 
@@ -2081,7 +2081,7 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
 		int rc;
 
 		/* might as well read a page, it is fast enough */
-		rc = cifs_readpage_worker(file, *pagep, &offset);
+		rc = cifs_readpage_worker(file, *pagep, &offset_of_page_start);
 
 		/* we do not need to pass errors back
 		   e.g. if we do not have read access to the file