Using folios instead of pages removes several calls to compound_head(),
shrinking the kernel by 1089 bytes of text.

Link: https://lkml.kernel.org/r/20220617175020.717127-8-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>