mm, compaction: terminate async compaction when rescheduling

Async compaction terminates prematurely when need_resched(), see
compact_checklock_irqsave().  This can never trigger, however, if the
cond_resched() in isolate_migratepages_range() always takes care of the
scheduling.

If the cond_resched() actually triggers, then terminate this pageblock
scan for async compaction as well.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 217a6ad9a20e..56331f5124ba 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -494,8 +494,13 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
                         return 0;
         }
 
+        if (cond_resched()) {
+                /* Async terminates prematurely on need_resched() */
+                if (cc->mode == MIGRATE_ASYNC)
+                        return 0;
+        }
+
         /* Time to isolate some pages for migration */
-        cond_resched();
         for (; low_pfn < end_pfn; low_pfn++) {
                 /* give a chance to irqs before checking need_resched() */
                 if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {