linux-kernel - [PATCH 2/7] migrate_pages(): remove unnecessary list_safe_reset

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Date:   Fri, 24 Jun 2022 10:53:04 +0800
From:   Huang Ying <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Zi Yan <ziy@...dia.com>, Yang Shi <shy828301@...il.com>
Subject: [PATCH 2/7] migrate_pages(): remove unnecessary list_safe_reset_next()

Before commit b5bade978e9b ("mm: migrate: fix the return value of
migrate_pages()"), the tail pages of THP will be put in the "from"
list directly.  So one of the loop cursors (page2) needs to be reset,
as is done in try_split_thp() via list_safe_reset_next().  But after
the commit, the tail pages of THP will be put in a dedicated
list (thp_split_pages).  That is, the "from" list will not be changed
during splitting.  So, it's unnecessary to call list_safe_reset_next()
anymore.

This is a code cleanup, no functionality changes are expected.

Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Yang Shi <shy828301@...il.com>
---
 mm/migrate.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index a271554be7a1..82444e7df9f1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1300,16 +1300,13 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 	return rc;
 }
 
-static inline int try_split_thp(struct page *page, struct page **page2,
-				struct list_head *from)
+static inline int try_split_thp(struct page *page, struct list_head *split_pages)
 {
-	int rc = 0;
+	int rc;
 
 	lock_page(page);
-	rc = split_huge_page_to_list(page, from);
+	rc = split_huge_page_to_list(page, split_pages);
 	unlock_page(page);
-	if (!rc)
-		list_safe_reset_next(page, *page2, lru);
 
 	return rc;
 }
@@ -1413,7 +1410,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				/* THP migration is unsupported */
 				if (is_thp) {
 					nr_thp_failed++;
-					if (!try_split_thp(page, &page2, &thp_split_pages)) {
+					if (!try_split_thp(page, &thp_split_pages)) {
 						nr_thp_split++;
 						goto retry;
 					}
@@ -1432,7 +1429,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				 */
 				if (is_thp && !nosplit) {
 					nr_thp_failed++;
-					if (!try_split_thp(page, &page2, &thp_split_pages)) {
+					if (!try_split_thp(page, &thp_split_pages)) {
 						nr_thp_split++;
 						goto retry;
 					}
-- 
2.30.2