From: Liu Shixin <liushixin2@huawei.com>
Date: Fri, 15 Sep 2023 08:34:17 +0000 (+0800)
Subject: mm-vmscan-try-to-reclaim-swapcache-pages-if-no-swap-space-v6
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=ea2bfb36af7dc88d3d6917112f0c9ad7b9db972a;p=users%2Fjedix%2Flinux-maple.git

mm-vmscan-try-to-reclaim-swapcache-pages-if-no-swap-space-v6

fix NULL pointing derefence and hung task problem reported by Sachin

Link: https://lkml.kernel.org/r/20230915083417.3190512-1-liushixin2@huawei.com
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Tested-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sachin Sant <sachinp@linux.ibm.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e78235927dee..96abaa5a973e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -324,7 +324,8 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
 			return true;
 		/* Is there any swapcache pages to reclaim? */
 		if (total_swapcache_pages() > 0) {
-			sc->swapcache_only = 1;
+			if (sc)
+				sc->swapcache_only = 1;
 			return true;
 		}
 	} else {
@@ -333,7 +334,8 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
 			return true;
 		/* Is there any swapcache pages in memcg to reclaim? */
 		if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) {
-			sc->swapcache_only = 1;
+			if (sc)
+				sc->swapcache_only = 1;
 			return true;
 		}
 	}
@@ -1597,19 +1599,6 @@ static bool skip_cma(struct folio *folio, struct scan_control *sc)
 }
 #endif
 
-static bool skip_isolate(struct folio *folio, struct scan_control *sc,
-			 enum lru_list lru)
-{
-	if (folio_zonenum(folio) > sc->reclaim_idx)
-		return true;
-	if (skip_cma(folio, sc))
-		return true;
-	if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
-	    !folio_test_swapcache(folio)))
-		return true;
-	return false;
-}
-
 /*
  * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
  *
@@ -1656,7 +1645,8 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 		nr_pages = folio_nr_pages(folio);
 		total_scan += nr_pages;
 
-		if (skip_isolate(folio, sc, lru)) {
+		if (folio_zonenum(folio) > sc->reclaim_idx ||
+				skip_cma(folio, sc)) {
 			nr_skipped[folio_zonenum(folio)] += nr_pages;
 			move_to = &folios_skipped;
 			goto move;
@@ -1671,6 +1661,15 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 		 */
 		scan += nr_pages;
 
+		/*
+		 * Count non-swapcache too because the swapcache pages may
+		 * be rare and it takes too much times here if not count
+		 * the non-swapcache pages.
+		 */
+		if (unlikely(sc->swapcache_only && !is_file_lru(lru) &&
+		    !folio_test_swapcache(folio)))
+			goto move;
+
 		if (!folio_test_lru(folio))
 			goto move;
 		if (!sc->may_unmap && folio_mapped(folio))