[PATCH 04/14] lru/compaction: use per lruvec lock in isolate_migratepages_block

[Alex Shi <alex.shi@linux.alibaba.com>]

Using lruvec locking to replace pgdat lru_lock. and then unfold
compact_unlock_should_abort() to fit the replacement.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Qian Cai <cai@lca.pw>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/compaction.c | 48 ++++++++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 18 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 9a737f343183..8877f38410d8 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -785,7 +785,7 @@ static bool too_many_isolated(pg_data_t *pgdat)
 	unsigned long nr_scanned = 0, nr_isolated = 0;
 	struct lruvec *lruvec;
 	unsigned long flags = 0;
-	bool locked = false;
+	struct lruvec *locked_lruvec = NULL;
 	struct page *page = NULL, *valid_page = NULL;
 	unsigned long start_pfn = low_pfn;
 	bool skip_on_failure = false;
@@ -845,11 +845,20 @@ static bool too_many_isolated(pg_data_t *pgdat)
 		 * contention, to give chance to IRQs. Abort completely if
 		 * a fatal signal is pending.
 		 */
-		if (!(low_pfn % SWAP_CLUSTER_MAX)
-		    && compact_unlock_should_abort(&pgdat->lruvec.lru_lock,
-					    flags, &locked, cc)) {
-			low_pfn = 0;
-			goto fatal_pending;
+		if (!(low_pfn % SWAP_CLUSTER_MAX)) {
+			if (locked_lruvec) {
+				spin_unlock_irqrestore(&locked_lruvec->lru_lock, flags);
+				locked_lruvec = NULL;
+			}
+
+			if (fatal_signal_pending(current)) {
+				cc->contended = true;
+
+				low_pfn = 0;
+				goto fatal_pending;
+			}
+
+			cond_resched();
 		}
 
 		if (!pfn_valid_within(low_pfn))
@@ -918,10 +927,10 @@ static bool too_many_isolated(pg_data_t *pgdat)
 			 */
 			if (unlikely(__PageMovable(page)) &&
 					!PageIsolated(page)) {
-				if (locked) {
-					spin_unlock_irqrestore(&pgdat->lruvec.lru_lock,
+				if (locked_lruvec) {
+					spin_unlock_irqrestore(&locked_lruvec->lru_lock,
 									flags);
-					locked = false;
+					locked_lruvec = NULL;
 				}
 
 				if (!isolate_movable_page(page, isolate_mode))
@@ -947,10 +956,14 @@ static bool too_many_isolated(pg_data_t *pgdat)
 		if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))
 			goto isolate_fail;
 
+		lruvec = mem_cgroup_page_lruvec(page, pgdat);
+
 		/* If we already hold the lock, we can skip some rechecking */
-		if (!locked) {
-			locked = compact_lock_irqsave(&pgdat->lruvec.lru_lock,
-								&flags, cc);
+		if (lruvec != locked_lruvec) {
+			if (compact_lock_irqsave(&lruvec->lru_lock, &flags, cc))
+				locked_lruvec = lruvec;
+
+			sync_lruvec_pgdat(lruvec, pgdat);
 
 			/* Try get exclusive access under lock */
 			if (!skip_updated) {
@@ -974,7 +987,6 @@ static bool too_many_isolated(pg_data_t *pgdat)
 			}
 		}
 
-		lruvec = mem_cgroup_page_lruvec(page, pgdat);
 
 		/* Try isolate the page */
 		if (__isolate_lru_page(page, isolate_mode) != 0)
@@ -1015,9 +1027,9 @@ static bool too_many_isolated(pg_data_t *pgdat)
 		 * page anyway.
 		 */
 		if (nr_isolated) {
-			if (locked) {
-				spin_unlock_irqrestore(&pgdat->lruvec.lru_lock, flags);
-				locked = false;
+			if (locked_lruvec) {
+				spin_unlock_irqrestore(&locked_lruvec->lru_lock, flags);
+				locked_lruvec = NULL;
 			}
 			putback_movable_pages(&cc->migratepages);
 			cc->nr_migratepages = 0;
@@ -1042,8 +1054,8 @@ static bool too_many_isolated(pg_data_t *pgdat)
 		low_pfn = end_pfn;
 
 isolate_abort:
-	if (locked)
-		spin_unlock_irqrestore(&pgdat->lruvec.lru_lock, flags);
+	if (locked_lruvec)
+		spin_unlock_irqrestore(&locked_lruvec->lru_lock, flags);
 
 	/*
 	 * Updated the cached scanner pfn once the pageblock has been scanned
-- 
1.8.3.1