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SubjectRe: [PATCH 2/7] migrate_pages(): remove unnecessary list_safe_reset_next()
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On 6/24/2022 10:53 AM, 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" <ying.huang@intel.com>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Yang Shi <shy828301@gmail.com>
> ---

Looks good to me.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.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;
> }

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