Re: [PATCH 1/3] list_bl: Add hlist_bl_add_before/behind helpers

Mike Snitzer
2019-02-28T21:32:08Z

On Thu, Dec 20 2018 at 1:06pm -0500,
Nikos Tsironis <ntsironis@arrikto.com> wrote:

> Add hlist_bl_add_before/behind helpers to add an element before/after an
> existing element in a bl_list.
>
> Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
> Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
> ---
> include/linux/list_bl.h | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
> index 3fc2cc57ba1b..2fd918e5fd48 100644
> --- a/include/linux/list_bl.h
> +++ b/include/linux/list_bl.h
> @@ -86,6 +86,33 @@ static inline void hlist_bl_add_head(struct hlist_bl_node *n,
> hlist_bl_set_first(h, n);
> }
>
> +static inline void hlist_bl_add_before(struct hlist_bl_node *n,
> + struct hlist_bl_node *next)
> +{
> + struct hlist_bl_node **pprev = next->pprev;
> +
> + n->pprev = pprev;
> + n->next = next;
> + next->pprev = &n->next;
> +
> + /* pprev may be `first`, so be careful not to lose the lock bit */
> + WRITE_ONCE(*pprev,
> + (struct hlist_bl_node *)
> + ((unsigned long)n |
> + ((unsigned long)*pprev & LIST_BL_LOCKMASK)));
> +}
> +
> +static inline void hlist_bl_add_behind(struct hlist_bl_node *n,
> + struct hlist_bl_node *prev)
> +{
> + n->next = prev->next;
> + n->pprev = &prev->next;
> + WRITE_ONCE(prev->next, n);
> +
> + if (n->next)
> + n->next->pprev = &n->next;
> +}
> +
> static inline void __hlist_bl_del(struct hlist_bl_node *n)
> {
> struct hlist_bl_node *next = n->next;
> --
> 2.11.0

Hi Paul and Christoph,

You've added your Signed-off-by to include/linux/list_bl.h commits in
the past. I'm not sure how this proposed patch should be handled.

These new hlist_bl_add_{before,behind} changes are a prereq for
dm-snapshot changes that Nikos has proposed, please see:
https://patchwork.kernel.org/patch/10739265/

Any assistance/review you, or others on LKML, might be able to provide
would be appreciated.

Thanks,
Mike