On Thu 17-09-20 21:00:39, Yu Zhao wrote:
> This patch replaces the only open-coded lru list addition with
> add_page_to_lru_list().
>
> Before this patch, we have:
> update_lru_size()
> list_move()
>
> After this patch, we have:
> list_del()
> add_page_to_lru_list()
> update_lru_size()
> list_add()
>
> The only side effect is that page->lru is temporarily poisoned
> after a page is deleted from its old list, which shouldn't be a
> problem.
"because the lru lock is held" right?
Please always be explicit about your reasoning. "It shouldn't be a
problem" without further justification is just pointless for anybody
reading the code later on.
> Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> ---
> mm/vmscan.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 9727dd8e2581..503fc5e1fe32 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1850,8 +1850,8 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
> while (!list_empty(list)) {
> page = lru_to_page(list);
> VM_BUG_ON_PAGE(PageLRU(page), page);
> + list_del(&page->lru);
> if (unlikely(!page_evictable(page))) {
> - list_del(&page->lru);
> spin_unlock_irq(&pgdat->lru_lock);
> putback_lru_page(page);
> spin_lock_irq(&pgdat->lru_lock);
> @@ -1862,9 +1862,7 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
> SetPageLRU(page);
> lru = page_lru(page);
>
> - nr_pages = thp_nr_pages(page);
> - update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
> - list_move(&page->lru, &lruvec->lists[lru]);
> + add_page_to_lru_list(page, lruvec, lru);
>
> if (put_page_testzero(page)) {
> __ClearPageLRU(page);
> @@ -1878,6 +1876,7 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
> } else
> list_add(&page->lru, &pages_to_free);
> } else {
> + nr_pages = thp_nr_pages(page);
> nr_moved += nr_pages;
> if (PageActive(page))
> workingset_age_nonresident(lruvec, nr_pages);
> --
> 2.28.0.681.g6f77f65b4e-goog
--
Michal Hocko
SUSE Labs
