Re: [PATCH 3/3] mm/swap: remove unneeded swap_active_head

[Chris Li <chrisl@kernel.org>]

Hi Andrew,

Please drop/ignore this patch series that removes the
swap_active_head. I just received the patch from YoungJun. Just as I
worried, YoungJun is indeed using the swap_active_head in his swap
tiers patch series. Let's not remove it.

I copy/paste from YoungJun's patches here. It has confirmed usage of that list.

+
+       p = plist_first_entry(&swap_active_head, struct swap_info_struct, list);
+       for_each_active_tier(tier) {
+               plist_for_each_entry_continue(p, &swap_active_head, list) {
+                       if (p->tier_off_mask != DEFAULT_OFF_MASK)

Chris

On Thu, Oct 9, 2025 at 6:28 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Thu, 9 Oct 2025 15:47:06 +0800 Baoquan He <bhe@redhat.com> wrote:
>
> > On 10/08/25 at 08:26pm, Andrew Morton wrote:
> > > On Wed,  1 Oct 2025 12:34:36 +0800 Baoquan He <bhe@redhat.com> wrote:
> > >
> > > > There's no user of swap_active_head, remove it now.
> > > >
> > > > ...
> > > >
> > > > @@ -2553,8 +2545,6 @@ static void _enable_swap_info(struct swap_info_struct *si)
> > > >
> > > >   assert_spin_locked(&swap_lock);
> > > >
> > > > - plist_add(&si->list, &swap_active_head);
> > > > -
> > >
> > > There's a large comment in _enable_swap_info() which needs to be
> > > removed or updated?
> >
> > This patchset depends on below patchset:
> > [PATCH v3 0/2] mm/swapfile.c: select the swap device with default priority round robin
>
> Oh, OK, sorry, missed that.
>
> (When I'm working on the post-merge-window patch pile (700+ emails) I
> go in reverse-time order, so highlighting dependencies like this helps!)
>
> > By the way, Chris worried the plist swap_active_head could be reused by
> > the ongoing swap-tier work and suggested to hold off this patchset till
> > swap-tier work is clear. Now seems it won't impact swap-tier, I will
> > send a v2 against mm-new.
>
> OK.
>
> Is Baoquan's "[PATCH v3 0/2] mm/swapfile.c: select the swap device with
> default priority round robin" series still considered good to merge?