filemap: Handle AOP_TRUNCATED_PAGE in do_read_cache_folio()

If the call to filler() returns AOP_TRUNCATED_PAGE, we need to
retry the page cache lookup.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

mm/filemap.c

@@ -3524,8 +3524,10 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
 	folio_clear_error(folio);
 filler:
 	err = filler(file, folio);
-	if (err < 0) {
+	if (err) {
 		folio_put(folio);
+		if (err == AOP_TRUNCATED_PAGE)
+			goto repeat;
 		return ERR_PTR(err);
 	}