[XFS] Export pagevec_lookup for use on the XFS page writeout path, for dealing with delayed allocate and unwritten extents (as well).

Signed-off-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Nathan Scott <[e-mail]>

mm/swap.c

···
 	return pagevec_count(pvec);
 }
 
+EXPORT_SYMBOL(pagevec_lookup);
+
 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 		pgoff_t *index, int tag, unsigned nr_pages)
 {