mm/swap: add folio_throttle_swaprate

The only use of the page argument to cgroup_throttle_swaprate() is to get
the node ID, and this will be the same for all pages in the folio, so just
pass in the first page of the folio.

Link: https://lkml.kernel.org/r/20220504182857.4013401-18-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/swap.h

@@ -640,6 +640,10 @@ static inline void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 {
 }
 #endif
+static inline void folio_throttle_swaprate(struct folio *folio, gfp_t gfp)
+{
+	cgroup_throttle_swaprate(&folio->page, gfp);
+}
 
 #ifdef CONFIG_MEMCG_SWAP
 void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry);