cached disk pages are not going to be swapped out, they're just freed (because these pages are already "out" in the same place swapland is)
if your cached disk pages keep getting hit and are "recent", they're going to stay in, and your old untouched working pages are going to be swapped out, to make room either for new working pages because you've just loaded new programs or data, or to make room for more disk pages to be cached because your page cache accesses are "busier" than some of your working pages.
you will swap out pages to make room for disk cache, but your cached disk pages will never be swapped out, they are just tossed (of course, after any dirty pages are written)
if your cached disk pages keep getting hit and are "recent", they're going to stay in, and your old untouched working pages are going to be swapped out, to make room either for new working pages because you've just loaded new programs or data, or to make room for more disk pages to be cached because your page cache accesses are "busier" than some of your working pages.
you will swap out pages to make room for disk cache, but your cached disk pages will never be swapped out, they are just tossed (of course, after any dirty pages are written)