On Tue, 4 Apr 2023 23:47:16 +0800 Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> wrote:
> The si->lock must be held when deleting the si from
> the available list.
>
> ...
>
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -679,6 +679,7 @@ static void __del_from_avail_list(struct swap_info_struct *p)
> {
> int nid;
>
> + assert_spin_locked(&p->lock);
> for_each_node(nid)
> plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]);
> }
> @@ -2434,8 +2435,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
> spin_unlock(&swap_lock);
> goto out_dput;
> }
> - del_from_avail_list(p);
> spin_lock(&p->lock);
> + del_from_avail_list(p);
> if (p->prio < 0) {
> struct swap_info_struct *si = p;
> int nid;
So we have
swap_avail_lock
swap_info_struct.lock
swap_cluster_info.lock
Is the ranking of these three clearly documented somewhere?
Did you test this with lockdep fully enabled?
I'm thinking that Aaron's a2468cc9bfdff ("swap: choose swap device
according to numa node") is the appropriate Fixes: target - do you
agree?
These functions use identifier `p' for the swap_info_struct*, whereas
most other code uses the much more sensible `si'. That's just rude.
But we shouldn't change that within this fix.
