linux-kernel - [PATCH v2 2/3] mm: fix numa stats for thp migration

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Message-Id: <20210108155813.2914586-2-shakeelb@google.com>
Date:   Fri,  8 Jan 2021 07:58:12 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Michal Hocko <mhocko@...nel.org>,
        Yang Shi <shy828301@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>, stable@...r.kernel.org
Subject: [PATCH v2 2/3] mm: fix numa stats for thp migration

Currently the kernel is not correctly updating the numa stats for
NR_FILE_PAGES and NR_SHMEM on THP migration. Fix that. For NR_FILE_DIRTY
and NR_ZONE_WRITE_PENDING, although at the moment there is no need to
handle THP migration as kernel still does not have write support for
file THP but to be more future proof, this patch adds the THP support
for those stats as well.

Fixes: e71769ae52609 ("mm: enable thp migration for shmem thp")
Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
Acked-by: Yang Shi <shy828301@...il.com>
Reviewed-by: Roman Gushchin <guro@...com>
Cc: <stable@...r.kernel.org>
---
Changes since v1:
- Fixed a typo

 mm/migrate.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 613794f6a433..c0efe921bca5 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -402,6 +402,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	struct zone *oldzone, *newzone;
 	int dirty;
 	int expected_count = expected_page_refs(mapping, page) + extra_count;
+	int nr = thp_nr_pages(page);
 
 	if (!mapping) {
 		/* Anonymous page without mapping */
@@ -437,7 +438,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	 */
 	newpage->index = page->index;
 	newpage->mapping = page->mapping;
-	page_ref_add(newpage, thp_nr_pages(page)); /* add cache reference */
+	page_ref_add(newpage, nr); /* add cache reference */
 	if (PageSwapBacked(page)) {
 		__SetPageSwapBacked(newpage);
 		if (PageSwapCache(page)) {
@@ -459,7 +460,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	if (PageTransHuge(page)) {
 		int i;
 
-		for (i = 1; i < HPAGE_PMD_NR; i++) {
+		for (i = 1; i < nr; i++) {
 			xas_next(&xas);
 			xas_store(&xas, newpage);
 		}
@@ -470,7 +471,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	 * to one less reference.
 	 * We know this isn't the last reference.
 	 */
-	page_ref_unfreeze(page, expected_count - thp_nr_pages(page));
+	page_ref_unfreeze(page, expected_count - nr);
 
 	xas_unlock(&xas);
 	/* Leave irq disabled to prevent preemption while updating stats */
@@ -493,17 +494,17 @@ int migrate_page_move_mapping(struct address_space *mapping,
 		old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
 		new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
 
-		__dec_lruvec_state(old_lruvec, NR_FILE_PAGES);
-		__inc_lruvec_state(new_lruvec, NR_FILE_PAGES);
+		__mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
+		__mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
 		if (PageSwapBacked(page) && !PageSwapCache(page)) {
-			__dec_lruvec_state(old_lruvec, NR_SHMEM);
-			__inc_lruvec_state(new_lruvec, NR_SHMEM);
+			__mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
+			__mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
 		}
 		if (dirty && mapping_can_writeback(mapping)) {
-			__dec_lruvec_state(old_lruvec, NR_FILE_DIRTY);
-			__dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
-			__inc_lruvec_state(new_lruvec, NR_FILE_DIRTY);
-			__inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
+			__mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr);
+			__mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr);
+			__mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr);
+			__mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr);
 		}
 	}
 	local_irq_enable();
-- 
2.29.2.729.g45daf8777d-goog