vmscan: return NODE_RECLAIM_NOSCAN in node_reclaim() when CONFIG_NUMA is n

Commit fa5e084e43 ("vmscan: do not unconditionally treat zones that
fail zone_reclaim() as full") changed the return value of
node_reclaim().  The original return value 0 means NODE_RECLAIM_SOME
after this commit.

While the return value of node_reclaim() when CONFIG_NUMA is n is not
changed.  This will leads to call zone_watermark_ok() again.

This patch fixes the return value by adjusting to NODE_RECLAIM_NOSCAN.
Since node_reclaim() is only called in page_alloc.c, move it to
mm/internal.h.

Link: http://lkml.kernel.org/r/20181113080436.22078-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

@@ -359,14 +359,8 @@ extern unsigned long vm_total_pages;
 extern int node_reclaim_mode;
 extern int sysctl_min_unmapped_ratio;
 extern int sysctl_min_slab_ratio;
-extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
 #else
 #define node_reclaim_mode 0
-static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
-				unsigned int order)
-{
-	return 0;
-}
 #endif
 
 extern int page_evictable(struct page *page);

mm/internal.h

@@ -444,6 +444,16 @@ static inline void mminit_validate_memmodel_limits(unsigned long *start_pfn,
 #define NODE_RECLAIM_SOME	0
 #define NODE_RECLAIM_SUCCESS	1
 
+#ifdef CONFIG_NUMA
+extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
+#else
+static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
+				unsigned int order)
+{
+	return NODE_RECLAIM_NOSCAN;
+}
+#endif
+
 extern int hwpoison_filter(struct page *p);
 
 extern u32 hwpoison_filter_dev_major;