mm: compaction: abort compaction loop if lock is contended or run too long

isolate_migratepages_range() might isolate no pages if for example when
zone->lru_lock is contended and running asynchronous compaction. In this
case, we should abort compaction, otherwise, compact_zone will run a
useless loop and make zone->lru_lock is even contended.

An additional check is added to ensure that cc.migratepages and
cc.freepages get properly drained whan compaction is aborted.

[minchan@kernel.org: Putback pages isolated for migration if aborting]
[akpm@linux-foundation.org: compact_zone_order requires non-NULL arg contended]
[akpm@linux-foundation.org: make compact_zone_order() require non-NULL arg `contended']
[minchan@kernel.org: Putback pages isolated for migration if aborting]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 1f61bcbd6262..0649cc1b3479 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -70,8 +70,7 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
 
                 /* async aborts if taking too long or contended */
                 if (!cc->sync) {
-                        if (cc->contended)
-                                *cc->contended = true;
+                        cc->contended = true;
                         return false;
                 }
 
@@ -688,7 +687,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 
         /* Perform the isolation */
         low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
-        if (!low_pfn)
+        if (!low_pfn || cc->contended)
                 return ISOLATE_ABORT;
 
         cc->migrate_pfn = low_pfn;
@@ -848,6 +847,8 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
                 switch (isolate_migratepages(zone, cc)) {
                 case ISOLATE_ABORT:
                         ret = COMPACT_PARTIAL;
+                        putback_lru_pages(&cc->migratepages);
+                        cc->nr_migratepages = 0;
                         goto out;
                 case ISOLATE_NONE:
                         continue;
@@ -896,6 +897,7 @@ static unsigned long compact_zone_order(struct zone *zone,
                                  bool sync, bool *contended,
                                  struct page **page)
 {
+        unsigned long ret;
         struct compact_control cc = {
                 .nr_freepages = 0,
                 .nr_migratepages = 0,
@@ -903,13 +905,18 @@ static unsigned long compact_zone_order(struct zone *zone,
                 .migratetype = allocflags_to_migratetype(gfp_mask),
                 .zone = zone,
                 .sync = sync,
-                .contended = contended,
                 .page = page,
         };
         INIT_LIST_HEAD(&cc.freepages);
         INIT_LIST_HEAD(&cc.migratepages);
 
-        return compact_zone(zone, &cc);
+        ret = compact_zone(zone, &cc);
+
+        VM_BUG_ON(!list_empty(&cc.freepages));
+        VM_BUG_ON(!list_empty(&cc.migratepages));
+
+        *contended = cc.contended;
+        return ret;
 }
 
 int sysctl_extfrag_threshold = 500;