Re: [RFC PATCH v4 1/3] mm/zswap: release retired pools via queue_rcu_work() instead of synchronize_rcu()

[Jianyue Wu]

On Mon, Aug 31, 2026 at 11:20 PM Yosry Ahmed <yosry@xxxxxxxxxx> wrote:
>
> On Sun, Aug 30, 2026 at 4:47 AM Jianyue Wu <wujianyue000@xxxxxxxxx> wrote:
> >
> > When a pool's last reference is dropped, __zswap_pool_empty() removes it
> > from the pool list and schedules __zswap_pool_release(), which calls
> > synchronize_rcu() to wait for readers before tearing the pool down.
> >
> > synchronize_rcu() is a synchronous, potentially long wait.  Replace it
> > with queue_rcu_work(): __zswap_pool_empty() hands the pool to
> > queue_rcu_work(), which waits for a grace period asynchronously and then
> > runs __zswap_pool_release() from a worker for the sleepable teardown
> > (__zswap_pool_empty() can run in atomic context and must not block).
> > The grace-period guarantee is unchanged; the retirement path just no
> > longer blocks on it.
> >
> > Suggested-by: Yosry Ahmed <yosry@xxxxxxxxxx>
> > Signed-off-by: Jianyue Wu <wujianyue000@xxxxxxxxx>
>
> Why are the patches still tagged RFC?
Exactly, should be removed, I dropped the RFC tag in the new version.

> Anyway, with one nit below:
>
> Acked-by: Yosry Ahmed <yosry@xxxxxxxxxx>
>
> > ---
> >  mm/zswap.c | 12 +++++-------
> >  1 file changed, 5 insertions(+), 7 deletions(-)
> >
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index 37f34e406c8e..0bb30e58950a 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -155,7 +155,7 @@ struct zswap_pool {
> >         struct crypto_acomp_ctx __percpu *acomp_ctx;
> >         struct percpu_ref ref;
> >         struct list_head list;
> > -       struct work_struct release_work;
> > +       struct rcu_work release_work;
>
> Seems like the convention is to use rwork in the name instead of work.
Good point, I renamed it to release_rwork in the new version.

Best regards,
Jianyue