On Thu, Jun 27, 2019 at 12:48:24PM +0200, Christoph Hellwig wrote:
> We have a very common pattern where we want to delete the first entry
> from a list and return it as the properly typed container structure.
>
> Add two helpers to implement this behavior.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
LGTM,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> include/linux/list.h | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/include/linux/list.h b/include/linux/list.h
> index e951228db4b2..ba6e27d2235a 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -500,6 +500,39 @@ static inline void list_splice_tail_init(struct list_head *list,
> pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
> })
>
> +/**
> + * list_pop - delete the first entry from a list and return it
> + * @list: the list to take the element from.
> + *
> + * Return the list entry after @list. If @list is empty return NULL.
> + */
> +static inline struct list_head *list_pop(struct list_head *list)
> +{
> + struct list_head *pos = READ_ONCE(list->next);
> +
> + if (pos == list)
> + return NULL;
> + list_del(pos);
> + return pos;
> +}
> +
> +/**
> + * list_pop_entry - delete the first entry from a list and return the
> + * containing structure
> + * @list: the list to take the element from.
> + * @type: the type of the struct this is embedded in.
> + * @member: the name of the list_head within the struct.
> + *
> + * Return the containing structure for the list entry after @list. If @list
> + * is empty return NULL.
> + */
> +#define list_pop_entry(list, type, member) \
> +({ \
> + struct list_head *pos__ = list_pop(list); \
> + \
> + pos__ ? list_entry(pos__, type, member) : NULL; \
> +})
> +
> /**
> * list_next_entry - get the next element in list
> * @pos: the type * to cursor
> --
> 2.20.1
>
