mm/page_alloc: remove nr_free_pagecache_pages()

nr_free_pagecache_pages() isn't used outside page_alloc.c anymore - and
the name does not really help to understand what's going on.  Let's
open-code it instead and add a comment.

Signed-off-by: David Hildenbrand <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Wei Yang <[email protected]>
Reviewed-by: Pankaj Gupta <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Huang Ying <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

Author: davidhildenbrand

include/linux/swap.h

@@ -328,7 +328,6 @@ void workingset_update_node(struct xa_node *node);
 /* linux/mm/page_alloc.c */
 extern unsigned long totalreserve_pages;
 extern unsigned long nr_free_buffer_pages(void);
-extern unsigned long nr_free_pagecache_pages(void);
 
 /* Definition of global_zone_page_state not available yet */
 #define nr_free_pages() global_zone_page_state(NR_FREE_PAGES)

mm/page_alloc.c

@@ -5186,19 +5186,6 @@ unsigned long nr_free_buffer_pages(void)
 }
 EXPORT_SYMBOL_GPL(nr_free_buffer_pages);
 
-/**
- * nr_free_pagecache_pages - count number of pages beyond high watermark
- *
- * nr_free_pagecache_pages() counts the number of pages which are beyond the
- * high watermark within all zones.
- *
- * Return: number of pages beyond high watermark within all zones.
- */
-unsigned long nr_free_pagecache_pages(void)
-{
-	return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
-}
-
 static inline void show_node(struct zone *zone)
 {
 	if (IS_ENABLED(CONFIG_NUMA))
@@ -5920,7 +5907,8 @@ void __ref build_all_zonelists(pg_data_t *pgdat)
 		__build_all_zonelists(pgdat);
 		/* cpuset refresh routine should be here */
 	}
-	vm_total_pages = nr_free_pagecache_pages();
+	/* Get the number of free pages beyond high watermark in all zones. */
+	vm_total_pages = nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE));
 	/*
 	 * Disable grouping by mobility if the number of pages in the
 	 * system is too low to allow the mechanism to work. It would be