2022-07-11 09:06:34

by Huang, Ying

Subject: [PATCH -V2 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" <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: Yang Shi <[email protected]>
---
mm/migrate.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 472335f0aaa3..794312072eb3 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1301,16 +1301,13 @@ 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;
}
@@ -1414,7 +1411,7 @@ 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;
}
@@ -1433,7 +1430,7 @@ 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

2022-07-11 12:30:14

by Oscar Salvador

Subject: Re: [PATCH -V2 2/7] migrate_pages(): remove unnecessary list_safe_reset_next()

On Mon, Jul 11, 2022 at 04:49:43PM +0800, Huang Ying wrote:
> 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" <[email protected]>
> Reviewed-by: Baolin Wang <[email protected]>
> Cc: Zi Yan <[email protected]>
> Cc: Yang Shi <[email protected]>

Reviewed-by: Oscar Salvador <[email protected]>


--
Oscar Salvador
SUSE Labs