[PATCH v2 1/1] mm: reduce NODE_RECLAIM_xxx and change to enum

[Petr Tesarik <ptesarik@suse.com>]

Change node_reclaim() to return an enum indicating whether any
pages have been reclaimed, because that's all the information
needed by the only caller, get_page_from_freelist().

This leads to the following translation of the old macro
identifiers to the new enum values:

- NODE_RECLAIM_NOSCAN  -> NODE_RECLAIM_NONE
- NODE_RECLAIM_FULL    -> NODE_RECLAIM_NONE
- NODE_RECLAIM_SOME    -> NODE_RECLAIM_SUCCESS
- NODE_RECLAIM_SUCCESS -> NODE_RECLAIM_SUCCESS

Originally, I was looking for occurences of NODE_RECLAIM_SOME
and NODE_RECLAIM_SUCCESS, but I couldn't find any. That's because
they are typecast from the result of a relational operator. This
seemed a bit fragile, so I dug a bit deeper and came up with this
proposed cleanup.

Signed-off-by: Petr Tesarik <ptesarik@suse.com>

--

Changes from v1:
- use an enum instead of a bool
---
 mm/internal.h   | 17 +++++++++--------
 mm/page_alloc.c | 19 ++++---------------
 mm/vmscan.c     | 18 +++++++++---------
 3 files changed, 22 insertions(+), 32 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 181e79f1d6a20..89b0ea28051c1 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1373,23 +1373,24 @@ static inline void mminit_verify_zonelist(void)
 }
 #endif /* CONFIG_DEBUG_MEMORY_INIT */
 
-#define NODE_RECLAIM_NOSCAN	-2
-#define NODE_RECLAIM_FULL	-1
-#define NODE_RECLAIM_SOME	0
-#define NODE_RECLAIM_SUCCESS	1
+enum node_reclaim {
+	NODE_RECLAIM_NONE,
+	NODE_RECLAIM_SUCCESS,
+};
 
 #ifdef CONFIG_NUMA
 extern int node_reclaim_mode;
 
-extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
+extern enum node_reclaim node_reclaim(struct pglist_data *pgdat,
+				      gfp_t gfp_mask, unsigned int order);
 extern int find_next_best_node(int node, nodemask_t *used_node_mask);
 #else
 #define node_reclaim_mode 0
 
-static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
-				unsigned int order)
+static inline enum node_reclaim node_reclaim(struct pglist_data *pgdat,
+					     gfp_t mask, unsigned int order)
 {
-	return NODE_RECLAIM_NOSCAN;
+	return NODE_RECLAIM_NONE;
 }
 static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
 {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f7db8f049bd23..83a1caac5ac9c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3899,8 +3899,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 		if (!zone_watermark_fast(zone, order, mark,
 				       ac->highest_zoneidx, alloc_flags,
 				       gfp_mask)) {
-			int ret;
-
 			if (cond_accept_memory(zone, order, alloc_flags))
 				goto try_this_zone;
 
@@ -3921,22 +3919,13 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 			    !zone_allows_reclaim(zonelist_zone(ac->preferred_zoneref), zone))
 				continue;
 
-			ret = node_reclaim(zone->zone_pgdat, gfp_mask, order);
-			switch (ret) {
-			case NODE_RECLAIM_NOSCAN:
-				/* did not scan */
-				continue;
-			case NODE_RECLAIM_FULL:
-				/* scanned but unreclaimable */
+			if (node_reclaim(zone->zone_pgdat, gfp_mask, order) == NODE_RECLAIM_NONE)
 				continue;
-			default:
-				/* did we reclaim enough */
-				if (zone_watermark_ok(zone, order, mark,
-					ac->highest_zoneidx, alloc_flags))
-					goto try_this_zone;
 
+			/* did we reclaim enough */
+			if (!zone_watermark_ok(zone, order, mark,
+					       ac->highest_zoneidx, alloc_flags))
 				continue;
-			}
 		}
 
 try_this_zone:
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3f3ff25e561ac..d5bd55620ee9a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -7786,9 +7786,9 @@ static unsigned long __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask,
 	return sc->nr_reclaimed;
 }
 
-int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
+enum node_reclaim node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
 {
-	int ret;
+	unsigned long nr_reclaimed;
 	/* Minimum pages needed in order to stay on node */
 	const unsigned long nr_pages = 1 << order;
 	struct scan_control sc = {
@@ -7815,13 +7815,13 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
 	if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages &&
 	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <=
 	    pgdat->min_slab_pages)
-		return NODE_RECLAIM_FULL;
+		return NODE_RECLAIM_NONE;
 
 	/*
 	 * Do not scan if the allocation should not be delayed.
 	 */
 	if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC))
-		return NODE_RECLAIM_NOSCAN;
+		return NODE_RECLAIM_NONE;
 
 	/*
 	 * Only run node reclaim on the local node or on nodes that do not
@@ -7830,20 +7830,20 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
 	 * as wide as possible.
 	 */
 	if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id())
-		return NODE_RECLAIM_NOSCAN;
+		return NODE_RECLAIM_NONE;
 
 	if (test_and_set_bit_lock(PGDAT_RECLAIM_LOCKED, &pgdat->flags))
-		return NODE_RECLAIM_NOSCAN;
+		return NODE_RECLAIM_NONE;
 
-	ret = __node_reclaim(pgdat, gfp_mask, nr_pages, &sc) >= nr_pages;
+	nr_reclaimed = __node_reclaim(pgdat, gfp_mask, nr_pages, &sc);
 	clear_bit_unlock(PGDAT_RECLAIM_LOCKED, &pgdat->flags);
 
-	if (ret)
+	if (nr_reclaimed >= nr_pages)
 		count_vm_event(PGSCAN_ZONE_RECLAIM_SUCCESS);
 	else
 		count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
 
-	return ret;
+	return NODE_RECLAIM_SUCCESS;
 }
 
 #else
-- 
2.54.0