mm/compaction.c: remove unnecessary zone parameter in isolate_migratepages()

Like commit 40cacbcb32 ("mm, compaction: remove unnecessary zone
parameter in some instances"), remove unnecessary zone parameter.

No functional change.

Link: http://lkml.kernel.org/r/20190806151616.21107-1-lpf.vector@gmail.com
Signed-off-by: Pengfei Li <lpf.vector@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Qian Cai <cai@lca.pw>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

@@ -1737,8 +1737,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
  * starting at the block pointed to by the migrate scanner pfn within
  * compact_control.
  */
-static isolate_migrate_t isolate_migratepages(struct zone *zone,
-					struct compact_control *cc)
+static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
 {
 	unsigned long block_start_pfn;
 	unsigned long block_end_pfn;
@@ -1756,8 +1755,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 	 */
 	low_pfn = fast_find_migrateblock(cc);
 	block_start_pfn = pageblock_start_pfn(low_pfn);
-	if (block_start_pfn < zone->zone_start_pfn)
-		block_start_pfn = zone->zone_start_pfn;
+	if (block_start_pfn < cc->zone->zone_start_pfn)
+		block_start_pfn = cc->zone->zone_start_pfn;
 
 	/*
 	 * fast_find_migrateblock marks a pageblock skipped so to avoid
@@ -1787,8 +1786,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 		if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)))
 			cond_resched();
 
-		page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
-									zone);
+		page = pageblock_pfn_to_page(block_start_pfn,
+						block_end_pfn, cc->zone);
 		if (!page)
 			continue;
 
@@ -2169,7 +2168,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
 			cc->rescan = true;
 		}
 
-		switch (isolate_migratepages(cc->zone, cc)) {
+		switch (isolate_migratepages(cc)) {
 		case ISOLATE_ABORT:
 			ret = COMPACT_CONTENDED;
 			putback_movable_pages(&cc->migratepages);