[PATCH 7/8] Revert "vmscan: abort reclaim/compaction if compaction can proceed"

[Andrea Arcangeli <aarcange@redhat.com>]

This reverts commit e0c23279c9f800c403f37511484d9014ac83adec.

If reclaim runs with an high order allocation, it means compaction
failed. That means something went wrong with compaction so we can't
stop reclaim too. We can't assume it failed and was deferred because
of the too low watermarks in compaction_suitable only, it may have
failed for other reasons.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
 mm/vmscan.c |   32 +++++++++++---------------------
 1 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3421746..b1a3cb0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2106,19 +2106,14 @@ restart:
  *
  * If a zone is deemed to be full of pinned pages then just give it a light
  * scan then give up on it.
- *
- * This function returns true if a zone is being reclaimed for a costly
- * high-order allocation and compaction is either ready to begin or deferred.
- * This indicates to the caller that it should retry the allocation or fail.
  */
-static bool shrink_zones(int priority, struct zonelist *zonelist,
+static void shrink_zones(int priority, struct zonelist *zonelist,
 					struct scan_control *sc)
 {
 	struct zoneref *z;
 	struct zone *zone;
 	unsigned long nr_soft_reclaimed;
 	unsigned long nr_soft_scanned;
-	bool should_abort_reclaim = false;
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 					gfp_zone(sc->gfp_mask), sc->nodemask) {
@@ -2135,20 +2130,19 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
 				continue;	/* Let kswapd poll it */
 			if (COMPACTION_BUILD) {
 				/*
-				 * If we already have plenty of memory free for
-				 * compaction in this zone, don't free any more.
-				 * Even though compaction is invoked for any
-				 * non-zero order, only frequent costly order
-				 * reclamation is disruptive enough to become a
-				 * noticable problem, like transparent huge page
-				 * allocations.
+				 * If we already have plenty of memory
+				 * free for compaction, don't free any
+				 * more.  Even though compaction is
+				 * invoked for any non-zero order,
+				 * only frequent costly order
+				 * reclamation is disruptive enough to
+				 * become a noticable problem, like
+				 * transparent huge page allocations.
 				 */
 				if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
 					(compaction_suitable(zone, sc->order) ||
-					 compaction_deferred(zone))) {
-					should_abort_reclaim = true;
+					 compaction_deferred(zone)))
 					continue;
-				}
 			}
 			/*
 			 * This steals pages from memory cgroups over softlimit
@@ -2167,8 +2161,6 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
 
 		shrink_zone(priority, zone, sc);
 	}
-
-	return should_abort_reclaim;
 }
 
 static bool zone_reclaimable(struct zone *zone)
@@ -2233,9 +2225,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 		sc->nr_scanned = 0;
 		if (!priority)
 			disable_swap_token(sc->mem_cgroup);
-		if (shrink_zones(priority, zonelist, sc))
-			break;
-
+		shrink_zones(priority, zonelist, sc);
 		/*
 		 * Don't shrink slabs when reclaiming memory from
 		 * over limit cgroups

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