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bpf: refactor __bpf_list_del to take list node pointer

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Refactor __bpf_list_del to accept (head, struct list_head *n) instead of
(head, bool tail). The caller now passes the specific node to remove:
bpf_list_pop_front passes h->next, bpf_list_pop_back passes h->prev.

Prepares for introducing bpf_list_del(head, node) kfunc to remove an
arbitrary node when the user holds ownership.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260521032306.97118-2-kaitao.cheng@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kaitao Cheng 2026-05-21 11:22:59 +08:00 committed by Alexei Starovoitov
parent 3db0419c01
commit cb339ac61d
1 changed files with 15 additions and 8 deletions
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23
kernel/bpf/helpers.c
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@ -2550,37 +2550,44 @@ __bpf_kfunc int bpf_list_push_back_impl(struct bpf_list_head *head,
return bpf_list_push_back(head, node, meta__ign, off);
}
static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, bool tail)
static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head,
struct list_head *n)
{
struct list_head *n, *h = (void *)head;
struct list_head *h = (void *)head;
struct bpf_list_node_kern *node;
/* If list_head was 0-initialized by map, bpf_obj_init_field wasn't
* called on its fields, so init here
*/
if (unlikely(!h->next))
if (unlikely(!h->next)) {
INIT_LIST_HEAD(h);
return NULL;
}
if (list_empty(h))
return NULL;
n = tail ? h->prev : h->next;
node = container_of(n, struct bpf_list_node_kern, list_head);
if (WARN_ON_ONCE(READ_ONCE(node->owner) != head))
if (unlikely(READ_ONCE(node->owner) != head))
return NULL;
list_del_init(n);
WRITE_ONCE(node->owner, NULL);
/* Ensure __bpf_list_add() sees the node as unlinked. */
smp_store_release(&node->owner, NULL);
return (struct bpf_list_node *)n;
}
__bpf_kfunc struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head)
{
return __bpf_list_del(head, false);
struct list_head *h = (void *)head;
return __bpf_list_del(head, h->next);
}
__bpf_kfunc struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
{
return __bpf_list_del(head, true);
struct list_head *h = (void *)head;
return __bpf_list_del(head, h->prev);
}
__bpf_kfunc struct bpf_list_node *bpf_list_front(struct bpf_list_head *head)