On Fri, Jun 23, 2023 at 04:40:12PM +0000, Jiaqi Yan wrote:
> Traversal on llist (e.g. llist_for_each_safe) is only safe AFTER entries
> are deleted from the llist.
>
> llist_del_all are lock free with itself. folio_clear_hugetlb_hwpoison()s
> from __update_and_free_hugetlb_folio and memory_failure won't need
> explicit locking when freeing the raw_hwp_list.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>
(Sorry if stupid question...) folio_set_hugetlb_hwpoison() also calls
llist_for_each_safe() but it still traverses the list without calling
llist_del_all(). This convention applies only when removing item(s)?
Thanks,
Naoya Horiguchi
> ---
> mm/memory-failure.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 004a02f44271..c415c3c462a3 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1825,12 +1825,11 @@ static inline struct llist_head *raw_hwp_list_head(struct folio *folio)
>
> static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> {
> - struct llist_head *head;
> - struct llist_node *t, *tnode;
> + struct llist_node *t, *tnode, *head;
> unsigned long count = 0;
>
> - head = raw_hwp_list_head(folio);
> - llist_for_each_safe(tnode, t, head->first) {
> + head = llist_del_all(raw_hwp_list_head(folio));
> + llist_for_each_safe(tnode, t, head) {
> struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
>
> if (move_flag)
> @@ -1840,7 +1839,6 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
> kfree(p);
> count++;
> }
> - llist_del_all(head);
> return count;
> }
>
> --
> 2.41.0.162.gfafddb0af9-goog
>
>
>
