mm, compaction: rename COMPACT_PARTIAL to COMPACT_SUCCESS

COMPACT_PARTIAL has historically meant that compaction returned after
doing some work without fully compacting a zone.  It however didn't
distinguish if compaction terminated because it succeeded in creating
the requested high-order page.  This has changed recently and now we
only return COMPACT_PARTIAL when compaction thinks it succeeded, or the
high-order watermark check in compaction_suitable() passes and no
compaction needs to be done.

So at this point we can make the return value clearer by renaming it to
COMPACT_SUCCESS.  The next patch will remove some redundant tests for
success where compaction just returned COMPACT_SUCCESS.

Link: http://lkml.kernel.org/r/20160810091226.6709-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 12 insertions, 12 deletions

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 1bb58581301c..e88c037afe47 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -49,10 +49,10 @@ enum compact_result {
         COMPACT_CONTENDED,
 
         /*
-         * direct compaction partially compacted a zone and there might be
-         * suitable pages
+         * direct compaction terminated after concluding that the allocation
+         * should now succeed
          */
-        COMPACT_PARTIAL,
+        COMPACT_SUCCESS,
 };
 
 struct alloc_context; /* in mm/internal.h */
@@ -88,7 +88,7 @@ static inline bool compaction_made_progress(enum compact_result result)
          * that the compaction successfully isolated and migrated some
          * pageblocks.
          */
-        if (result == COMPACT_PARTIAL)
+        if (result == COMPACT_SUCCESS)
                 return true;
 
         return false;
diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
index c2ba402ab256..cbdb90b6b308 100644
--- a/include/trace/events/compaction.h
+++ b/include/trace/events/compaction.h
@@ -13,7 +13,7 @@
         EM( COMPACT_SKIPPED,            "skipped")              \
         EM( COMPACT_DEFERRED,           "deferred")             \
         EM( COMPACT_CONTINUE,           "continue")             \
-        EM( COMPACT_PARTIAL,            "partial")              \
+        EM( COMPACT_SUCCESS,            "success")              \
         EM( COMPACT_PARTIAL_SKIPPED,    "partial_skipped")      \
         EM( COMPACT_COMPLETE,           "complete")             \
         EM( COMPACT_NO_SUITABLE_PAGE,   "no_suitable_page")     \
diff --git a/mm/compaction.c b/mm/compaction.c
index 8e32778fba5b..335eeeed0c91 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1329,13 +1329,13 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
 
                 /* Job done if page is free of the right migratetype */
                 if (!list_empty(&area->free_list[migratetype]))
-                        return COMPACT_PARTIAL;
+                        return COMPACT_SUCCESS;
 
 #ifdef CONFIG_CMA
                 /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
                 if (migratetype == MIGRATE_MOVABLE &&
                         !list_empty(&area->free_list[MIGRATE_CMA]))
-                        return COMPACT_PARTIAL;
+                        return COMPACT_SUCCESS;
 #endif
                 /*
                  * Job done if allocation would steal freepages from
@@ -1343,7 +1343,7 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
                  */
                 if (find_suitable_fallback(area, order, migratetype,
                                                 true, &can_steal) != -1)
-                        return COMPACT_PARTIAL;
+                        return COMPACT_SUCCESS;
         }
 
         return COMPACT_NO_SUITABLE_PAGE;
@@ -1367,7 +1367,7 @@ static enum compact_result compact_finished(struct zone *zone,
  * compaction_suitable: Is this suitable to run compaction on this zone now?
  * Returns
  *   COMPACT_SKIPPED  - If there are too few free pages for compaction
- *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
+ *   COMPACT_SUCCESS  - If the allocation would succeed without compaction
  *   COMPACT_CONTINUE - If compaction should run now
  */
 static enum compact_result __compaction_suitable(struct zone *zone, int order,
@@ -1388,7 +1388,7 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
          */
         if (zone_watermark_ok(zone, order, watermark, classzone_idx,
                                                                 alloc_flags))
-                return COMPACT_PARTIAL;
+                return COMPACT_SUCCESS;
 
         /*
          * Watermarks for order-0 must be met for compaction. Note the 2UL.
@@ -1477,7 +1477,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
         ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
                                                         cc->classzone_idx);
         /* Compaction is likely to fail */
-        if (ret == COMPACT_PARTIAL || ret == COMPACT_SKIPPED)
+        if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
                 return ret;
 
         /* huh, compaction_suitable is returning something unexpected */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0fe8b7113868..981fc84e7434 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2495,7 +2495,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
                         continue;
 
                 switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
-                case COMPACT_PARTIAL:
+                case COMPACT_SUCCESS:
                 case COMPACT_CONTINUE:
                         return false;
                 default: