mm: rename RECLAIM_SWAP to RECLAIM_UNMAP

The name SWAP implies that we are dealing with anonymous pages only.  In
fact, the original patch that introduced the min_unmapped_ratio logic
was to fix an issue related to file pages.  Rename it to RECLAIM_UNMAP
to match what does.

Historically, commit a6dc60f8975a ("vmscan: rename sc.may_swap to
may_unmap") renamed .may_swap to .may_unmap, leaving RECLAIM_SWAP
behind.  commit 2e2e42598908 ("vmscan,memcg: reintroduce sc->may_swap")
reintroduced .may_swap for memory controller.

Signed-off-by: Zhihui Zhang <zzhsuny@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -3597,7 +3597,7 @@ int zone_reclaim_mode __read_mostly;
 #define RECLAIM_OFF 0
 #define RECLAIM_ZONE (1<<0)	/* Run shrink_inactive_list on the zone */
 #define RECLAIM_WRITE (1<<1)	/* Writeout pages during reclaim */
-#define RECLAIM_SWAP (1<<2)	/* Swap pages out during reclaim */
+#define RECLAIM_UNMAP (1<<2)	/* Unmap pages during reclaim */
 
 /*
  * Priority for ZONE_RECLAIM. This determines the fraction of pages
@@ -3639,12 +3639,12 @@ static long zone_pagecache_reclaimable(struct zone *zone)
 	long delta = 0;
 
 	/*
-	 * If RECLAIM_SWAP is set, then all file pages are considered
+	 * If RECLAIM_UNMAP is set, then all file pages are considered
 	 * potentially reclaimable. Otherwise, we have to worry about
 	 * pages like swapcache and zone_unmapped_file_pages() provides
 	 * a better estimate
 	 */
-	if (zone_reclaim_mode & RECLAIM_SWAP)
+	if (zone_reclaim_mode & RECLAIM_UNMAP)
 		nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
 	else
 		nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
@@ -3675,15 +3675,15 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 		.order = order,
 		.priority = ZONE_RECLAIM_PRIORITY,
 		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
-		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
+		.may_unmap = !!(zone_reclaim_mode & RECLAIM_UNMAP),
 		.may_swap = 1,
 	};
 
 	cond_resched();
 	/*
-	 * We need to be able to allocate from the reserves for RECLAIM_SWAP
+	 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
 	 * and we also need to be able to write out pages for RECLAIM_WRITE
-	 * and RECLAIM_SWAP.
+	 * and RECLAIM_UNMAP.
 	 */
 	p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
 	lockdep_set_current_reclaim_state(gfp_mask);