[Devel] [PATCH RHEL7 COMMIT] ms/mm: compaction: encapsulate defer reset logic

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-693.11.6.vz7.42.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.11.6.vz7.42.4
------>
commit 93ef5641dd2286302499a0adaf17161b376d00df
Author: Vlastimil Babka <vbabka at suse.cz>
Date:   Wed Jan 31 18:21:51 2018 +0300

    ms/mm: compaction: encapsulate defer reset logic
    
    Currently there are several functions to manipulate the deferred
    compaction state variables.  The remaining case where the variables are
    touched directly is when a successful allocation occurs in direct
    compaction, or is expected to be successful in the future by kswapd.
    Here, the lowest order that is expected to fail is updated, and in the
    case of successful allocation, the deferred status and counter is reset
    completely.
    
    Create a new function compaction_defer_reset() to encapsulate this
    functionality and make it easier to understand the code.  No functional
    change.
    
    Signed-off-by: Vlastimil Babka <vbabka at suse.cz>
    Acked-by: Mel Gorman <mgorman at suse.de>
    Reviewed-by: Rik van Riel <riel at redhat.com>
    Cc: Joonsoo Kim <iamjoonsoo.kim at lge.com>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
    (cherry picked from commit de6c60a6c115acaa721cfd499e028a413d1fcbf3)
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 include/linux/compaction.h | 16 ++++++++++++++++
 mm/compaction.c            |  9 ++++-----
 mm/page_alloc.c            |  5 +----
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 091d72e70d8a..7e1c76e3cd68 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -62,6 +62,22 @@ static inline bool compaction_deferred(struct zone *zone, int order)
 	return zone->compact_considered < defer_limit;
 }
 
+/*
+ * Update defer tracking counters after successful compaction of given order,
+ * which means an allocation either succeeded (alloc_success == true) or is
+ * expected to succeed.
+ */
+static inline void compaction_defer_reset(struct zone *zone, int order,
+		bool alloc_success)
+{
+	if (alloc_success) {
+		zone->compact_considered = 0;
+		zone->compact_defer_shift = 0;
+	}
+	if (order >= zone->compact_order_failed)
+		zone->compact_order_failed = order + 1;
+}
+
 /* Returns true if restarting compaction after many failures */
 static inline bool compaction_restarting(struct zone *zone, int order)
 {
diff --git a/mm/compaction.c b/mm/compaction.c
index 31ea5ed95194..f324cbaf923d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1150,12 +1150,11 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
 			compact_zone(zone, cc);
 
 		if (cc->order > 0) {
-			int ok = zone_watermark_ok(zone, cc->order,
-						low_wmark_pages(zone), 0, 0);
-			if (ok && cc->order >= zone->compact_order_failed)
-				zone->compact_order_failed = cc->order + 1;
+			if (zone_watermark_ok(zone, cc->order,
+						low_wmark_pages(zone), 0, 0))
+				compaction_defer_reset(zone, cc->order, false);
 			/* Currently async compaction is never deferred. */
-			else if (!ok && cc->sync)
+			else if (cc->sync)
 				defer_compaction(zone, cc->order);
 		}
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ec66148d09ba..691c9bdbede3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2683,10 +2683,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 				preferred_zone, migratetype);
 		if (page) {
 			preferred_zone->compact_blockskip_flush = false;
-			preferred_zone->compact_considered = 0;
-			preferred_zone->compact_defer_shift = 0;
-			if (order >= preferred_zone->compact_order_failed)
-				preferred_zone->compact_order_failed = order + 1;
+			compaction_defer_reset(preferred_zone, order, true);
 			count_vm_event(COMPACTSUCCESS);
 			return page;
 		}