The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a94b525241c0fff3598809131d7cfcfe1d572d8c Mon Sep 17 00:00:00 2001

From: Yafang Shao laoar.shao@gmail.com Date: Mon, 23 Sep 2019 15:36:54 -0700 Subject: [PATCH] mm/compaction.c: clear total_{migrate,free}_scanned before scanning a new zone

total_{migrate,free}_scanned will be added to COMPACTMIGRATE_SCANNED and COMPACTFREE_SCANNED in compact_zone(). We should clear them before scanning a new zone. In the proc triggered compaction, we forgot clearing them.

[laoar.shao@gmail.com: introduce a helper compact_zone_counters_init()] Link: http://lkml.kernel.org/r/1563869295-25748-1-git-send-email-laoar.shao@gmail.... [akpm@linux-foundation.org: expand compact_zone_counters_init() into its single callsite, per mhocko] [vbabka@suse.cz: squash compact_zone() list_head init as well] Link: http://lkml.kernel.org/r/1fb6f7da-f776-9e42-22f8-bbb79b030b98@suse.cz [akpm@linux-foundation.org: kcompactd_do_work(): avoid unnecessary initialization of cc.zone] Link: http://lkml.kernel.org/r/1563789275-9639-1-git-send-email-laoar.shao@gmail.c... Fixes: 7f354a548d1c ("mm, compaction: add vmstats for kcompactd work") Signed-off-by: Yafang Shao laoar.shao@gmail.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Reviewed-by: Vlastimil Babka vbabka@suse.cz Cc: David Rientjes rientjes@google.com Cc: Yafang Shao shaoyafang@didiglobal.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Michal Hocko mhocko@suse.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

diff --git a/mm/compaction.c b/mm/compaction.c index 777c088e9113..d99d59412c75 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2078,6 +2078,17 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) const bool sync = cc->mode != MIGRATE_ASYNC; bool update_cached;

+ /* + * These counters track activities during zone compaction. Initialize + * them before compacting a new zone. + */ + cc->total_migrate_scanned = 0; + cc->total_free_scanned = 0; + cc->nr_migratepages = 0; + cc->nr_freepages = 0; + INIT_LIST_HEAD(&cc->freepages); + INIT_LIST_HEAD(&cc->migratepages); + cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask); ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags, cc->classzone_idx); @@ -2281,10 +2292,6 @@ static enum compact_result compact_zone_order(struct zone *zone, int order, { enum compact_result ret; struct compact_control cc = { - .nr_freepages = 0, - .nr_migratepages = 0, - .total_migrate_scanned = 0, - .total_free_scanned = 0, .order = order, .search_order = order, .gfp_mask = gfp_mask, @@ -2305,8 +2312,6 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,

if (capture) current->capture_control = &capc; - INIT_LIST_HEAD(&cc.freepages); - INIT_LIST_HEAD(&cc.migratepages);

ret = compact_zone(&cc, &capc);

@@ -2408,8 +2413,6 @@ static void compact_node(int nid) struct zone *zone; struct compact_control cc = { .order = -1, - .total_migrate_scanned = 0, - .total_free_scanned = 0, .mode = MIGRATE_SYNC, .ignore_skip_hint = true, .whole_zone = true, @@ -2423,11 +2426,7 @@ static void compact_node(int nid) if (!populated_zone(zone)) continue;

- cc.nr_freepages = 0; - cc.nr_migratepages = 0; cc.zone = zone; - INIT_LIST_HEAD(&cc.freepages); - INIT_LIST_HEAD(&cc.migratepages);

compact_zone(&cc, NULL);

@@ -2529,8 +2528,6 @@ static void kcompactd_do_work(pg_data_t *pgdat) struct compact_control cc = { .order = pgdat->kcompactd_max_order, .search_order = pgdat->kcompactd_max_order, - .total_migrate_scanned = 0, - .total_free_scanned = 0, .classzone_idx = pgdat->kcompactd_classzone_idx, .mode = MIGRATE_SYNC_LIGHT, .ignore_skip_hint = false, @@ -2554,16 +2551,10 @@ static void kcompactd_do_work(pg_data_t *pgdat) COMPACT_CONTINUE) continue;

- cc.nr_freepages = 0; - cc.nr_migratepages = 0; - cc.total_migrate_scanned = 0; - cc.total_free_scanned = 0; - cc.zone = zone; - INIT_LIST_HEAD(&cc.freepages); - INIT_LIST_HEAD(&cc.migratepages); - if (kthread_should_stop()) return; + + cc.zone = zone; status = compact_zone(&cc, NULL);

if (status == COMPACT_SUCCESS) {