mm, pagevec: rename pagevec drained field

According to Vlastimil Babka, the drained field in pagevec is
potentially misleading because it might be interpreted as draining this
pagevec instead of the percpu lru pagevecs.  Rename the field for
clarity.

Link: http://lkml.kernel.org/r/20171019093346.ylahzdpzmoriyf4v@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pagevec.h

@@ -17,7 +17,7 @@ struct address_space;
 
 struct pagevec {
 	unsigned long nr;
-	bool drained;
+	bool percpu_pvec_drained;
 	struct page *pages[PAGEVEC_SIZE];
 };
 
@@ -53,7 +53,7 @@ static inline unsigned pagevec_lookup_tag(struct pagevec *pvec,
 static inline void pagevec_init(struct pagevec *pvec)
 {
 	pvec->nr = 0;
-	pvec->drained = false;
+	pvec->percpu_pvec_drained = false;
 }
 
 static inline void pagevec_reinit(struct pagevec *pvec)

mm/swap.c

@@ -833,9 +833,9 @@ EXPORT_SYMBOL(release_pages);
  */
 void __pagevec_release(struct pagevec *pvec)
 {
-	if (!pvec->drained) {
+	if (!pvec->percpu_pvec_drained) {
 		lru_add_drain();
-		pvec->drained = true;
+		pvec->percpu_pvec_drained = true;
 	}
 	release_pages(pvec->pages, pagevec_count(pvec));
 	pagevec_reinit(pvec);