Christoph Hellwig [off-list ref] wrote:

quoted

+		size_t offset = offset_in_folio(folio, start + __off);	\
+		if (xas_retry(&xas, folio))			\
 			continue;				\
+		if (WARN_ON(xa_is_value(folio)))		\
 			break;					\
+		if (WARN_ON(folio_test_hugetlb(folio)))		\
 			break;					\
+		while (offset < folio_size(folio)) {		\

Nit: I'd be tempted to use a for loop on offset here.

A while-loop makes more sense here.  The adjustment you need for offset
(ie. len) is overwritten after offset is altered at the end of the loop:

+			offset += len;				\
+			len = PAGE_SIZE;			\
 		}						\

So you'd have to move both of these into the for-incrementor expression, in
addition to moving in the initialiser expression, making the thing less
readable.

David