Re: [PATCH] llist: Don't reinvent the wheel but use existing llist API

From: NeilBrown
Date: Sun Feb 12 2017 - 23:56:44 EST


On Mon, Feb 13 2017, Byungchul Park wrote:

> Although llist provides proper APIs, they are not used. Make them used.
>
> Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
> ---
> drivers/md/bcache/closure.c | 15 ++-------------
> drivers/md/raid5.c | 4 +---
> drivers/vhost/scsi.c | 9 ++-------
> fs/file_table.c | 12 +++++-------
> fs/namespace.c | 12 +++++-------
> include/linux/llist.h | 3 +++
> kernel/irq_work.c | 6 +-----
> kernel/sched/core.c | 13 ++-----------
> mm/vmalloc.c | 8 +++-----
> 9 files changed, 24 insertions(+), 58 deletions(-)
>
...

> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 36c13e4..c82243a 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -359,11 +359,9 @@ static int release_stripe_list(struct r5conf *conf,
>
> head = llist_del_all(&conf->released_stripes);
> head = llist_reverse_order(head);
> - while (head) {
> + llist_for_each_entry(sh, head, release_list) {
> int hash;
>
> - sh = llist_entry(head, struct stripe_head, release_list);
> - head = llist_next(head);
> /* sh could be readded after STRIPE_ON_RELEASE_LIST is cleard */
> smp_mb();
> clear_bit(STRIPE_ON_RELEASE_LIST, &sh->state);

This one is wrong (I haven't checked the rest).
As soon a STRIPE_ON_RELEASE_LIST is cleared, the llist_node can be
reused, so we need to call llist_next *before* the rest of the code.
You have moved the call to afterwards.

You could possibly change it to use llist_for_each_entry_safe()

NeilBrown

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