[PATCH] mm: skip CMA pages when they are not available

["zhaoyang.huang" <zhaoyang.huang@xxxxxxxxxx>]

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

It is wasting of effort to reclaim CMA pages if they are not availabe
for current context during direct reclaim. Skip them when under corresponding
circumstance.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
 mm/vmscan.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd6637f..04424d9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2225,10 +2225,16 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 	unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
 	unsigned long skipped = 0;
 	unsigned long scan, total_scan, nr_pages;
+	bool cma_cap = true;
+	struct page *page;
 	LIST_HEAD(folios_skipped);
 
 	total_scan = 0;
 	scan = 0;
+	if ((IS_ENABLED(CONFIG_CMA)) && !current_is_kswapd()
+		&& (gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE))
+		cma_cap = false;
+
 	while (scan < nr_to_scan && !list_empty(src)) {
 		struct list_head *move_to = src;
 		struct folio *folio;
@@ -2239,7 +2245,10 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 		nr_pages = folio_nr_pages(folio);
 		total_scan += nr_pages;
 
-		if (folio_zonenum(folio) > sc->reclaim_idx) {
+		page = &folio->page;
+
+		if (folio_zonenum(folio) > sc->reclaim_idx ||
+			(get_pageblock_migratetype(page) == MIGRATE_CMA && !cma_cap)) {
 			nr_skipped[folio_zonenum(folio)] += nr_pages;
 			move_to = &folios_skipped;
 			goto move;
-- 
1.9.1