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Date:   Fri, 2 Jun 2023 11:12:04 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Mel Gorman <mgorman@techsingularity.net>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH 6/5] mm: compaction: have compaction_suitable() return bool
Message-ID: <20230602151204.GD161817@cmpxchg.org>
References: <20230519123959.77335-1-hannes@cmpxchg.org>
MIME-Version: 1.0
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In-Reply-To: <20230519123959.77335-1-hannes@cmpxchg.org>
Precedence: bulk

Since it only returns COMPACT_CONTINUE or COMPACT_SKIPPED now, a bool
return value simplifies the callsites.

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 include/linux/compaction.h |  6 ++--
 mm/compaction.c            | 64 ++++++++++++++++++--------------------
 mm/vmscan.c                |  6 ++--
 3 files changed, 36 insertions(+), 40 deletions(-)

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 9f7cf3e1bf89..57b16e69c19a 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -89,7 +89,7 @@ extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
 		const struct alloc_context *ac, enum compact_priority prio,
 		struct page **page);
 extern void reset_isolation_suitable(pg_data_t *pgdat);
-extern enum compact_result compaction_suitable(struct zone *zone, int order,
+extern bool compaction_suitable(struct zone *zone, int order,
 					       int highest_zoneidx);
 
 extern void compaction_defer_reset(struct zone *zone, int order,
@@ -107,10 +107,10 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat)
 {
 }
 
-static inline enum compact_result compaction_suitable(struct zone *zone, int order,
+static inline bool compaction_suitable(struct zone *zone, int order,
 						      int highest_zoneidx)
 {
-	return COMPACT_SKIPPED;
+	return false;
 }
 
 static inline void kcompactd_run(int nid)
diff --git a/mm/compaction.c b/mm/compaction.c
index fdee5f1ac5a1..d354d8af157c 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2205,9 +2205,9 @@ static enum compact_result compact_finished(struct compact_control *cc)
 	return ret;
 }
 
-static enum compact_result __compaction_suitable(struct zone *zone, int order,
-					int highest_zoneidx,
-					unsigned long wmark_target)
+static bool __compaction_suitable(struct zone *zone, int order,
+				  int highest_zoneidx,
+				  unsigned long wmark_target)
 {
 	unsigned long watermark;
 	/*
@@ -2227,27 +2227,20 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
 	watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
 				low_wmark_pages(zone) : min_wmark_pages(zone);
 	watermark += compact_gap(order);
-	if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
-						ALLOC_CMA, wmark_target))
-		return COMPACT_SKIPPED;
-
-	return COMPACT_CONTINUE;
+	return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
+				   ALLOC_CMA, wmark_target);
 }
 
 /*
  * 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_CONTINUE - If compaction should run now
  */
-enum compact_result compaction_suitable(struct zone *zone, int order,
-					int highest_zoneidx)
+bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx)
 {
-	enum compact_result ret;
-	int fragindex;
+	enum compact_result compact_result;
+	bool suitable;
 
-	ret = __compaction_suitable(zone, order, highest_zoneidx,
-				    zone_page_state(zone, NR_FREE_PAGES));
+	suitable = __compaction_suitable(zone, order, highest_zoneidx,
+					 zone_page_state(zone, NR_FREE_PAGES));
 	/*
 	 * fragmentation index determines if allocation failures are due to
 	 * low memory or external fragmentation
@@ -2264,17 +2257,24 @@ enum compact_result compaction_suitable(struct zone *zone, int order,
 	 * excessive compaction for costly orders, but it should not be at the
 	 * expense of system stability.
 	 */
-	if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
-		fragindex = fragmentation_index(zone, order);
-		if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
-			ret = COMPACT_NOT_SUITABLE_ZONE;
+	if (suitable) {
+		compact_result = COMPACT_CONTINUE;
+		if (order > PAGE_ALLOC_COSTLY_ORDER) {
+			int fragindex = fragmentation_index(zone, order);
+
+			if (fragindex >= 0 &&
+			    fragindex <= sysctl_extfrag_threshold) {
+				suitable = false;
+				compact_result = COMPACT_NOT_SUITABLE_ZONE;
+			}
+		}
+	} else {
+		compact_result = COMPACT_SKIPPED;
 	}
 
-	trace_mm_compaction_suitable(zone, order, ret);
-	if (ret == COMPACT_NOT_SUITABLE_ZONE)
-		ret = COMPACT_SKIPPED;
+	trace_mm_compaction_suitable(zone, order, compact_result);
 
-	return ret;
+	return suitable;
 }
 
 bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
@@ -2300,7 +2300,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 		available = zone_reclaimable_pages(zone) / order;
 		available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
 		if (__compaction_suitable(zone, order, ac->highest_zoneidx,
-					  available) == COMPACT_CONTINUE)
+					  available))
 			return true;
 	}
 
@@ -2341,11 +2341,10 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
 				      cc->highest_zoneidx, cc->alloc_flags))
 			return COMPACT_SUCCESS;
 
-		ret = compaction_suitable(cc->zone, cc->order,
-					  cc->highest_zoneidx);
 		/* Compaction is likely to fail */
-		if (ret == COMPACT_SKIPPED)
-			return ret;
+		if (!compaction_suitable(cc->zone, cc->order,
+					 cc->highest_zoneidx))
+			return COMPACT_SKIPPED;
 	}
 
 	/*
@@ -2846,7 +2845,7 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat)
 			continue;
 
 		if (compaction_suitable(zone, pgdat->kcompactd_max_order,
-					highest_zoneidx) == COMPACT_CONTINUE)
+					highest_zoneidx))
 			return true;
 	}
 
@@ -2888,8 +2887,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)
 				      min_wmark_pages(zone), zoneid, 0))
 			continue;
 
-		if (compaction_suitable(zone, cc.order,
-					zoneid) != COMPACT_CONTINUE)
+		if (!compaction_suitable(zone, cc.order, zoneid))
 			continue;
 
 		if (kthread_should_stop())
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c0cfa9b86b48..e9a8ca124982 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -6402,8 +6402,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
 				      sc->reclaim_idx, 0))
 			return false;
 
-		if (compaction_suitable(zone, sc->order,
-					sc->reclaim_idx) == COMPACT_CONTINUE)
+		if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
 			return false;
 	}
 
@@ -6599,8 +6598,7 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
 		return true;
 
 	/* Compaction cannot yet proceed. Do reclaim. */
-	if (compaction_suitable(zone, sc->order,
-				sc->reclaim_idx) == COMPACT_SKIPPED)
+	if (!compaction_suitable(zone, sc->order, sc->reclaim_idx))
 		return false;
 
 	/*
-- 
2.40.1