Re: [PATCH] zram: do not permit params change after init

[Brian Geffon <bgeffon@google.com>]

On Tue, Mar 10, 2026 at 10:01 AM Brian Geffon <bgeffon@google.com> wrote:
>
> On Tue, Mar 10, 2026 at 2:04 AM Sergey Senozhatsky
> <senozhatsky@chromium.org> wrote:
> >
> > First, algorithm_params_store(), like any sysfs handler,
> > should grab device init lock.
> >
> > Second, like any write() sysfs handler, it should grab
> > device init lock in exclusive mode.
>
> comp_algorithm_store() and recomp_algorithm_store()?

disregard, that happens in __comp_algorithm_store().

>
> >
> > Third, it should not permit change of algos' parameters
> > after device init, as this doesn't make sense - we cannot
> > compress with one C/D dict and then just change C/D dict
> > to a different one, for example.
> >
> > Fixes: 4eac932103a5d ("zram: introduce algorithm_params device attribute")
> > Cc: gao xu <gaoxu2@honor.com>
> > Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
>
> Acked-by: Brian Geffon <bgeffon@google.com>
>
> > ---
> >  drivers/block/zram/zram_drv.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index c41e1257243f..7551c5e664a9 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -1769,6 +1769,10 @@ static ssize_t algorithm_params_store(struct device *dev,
> >         if (prio < ZRAM_PRIMARY_COMP || prio >= ZRAM_MAX_COMPS)
> >                 return -EINVAL;
> >
> > +       guard(rwsem_write)(&zram->dev_lock);
> > +       if (init_done(zram))
> > +               return -EBUSY;
> > +
> >         ret = comp_params_store(zram, prio, level, dict_path, &deflate_params);
> >         return ret ? ret : len;
> >  }
> > --
> > 2.53.0.473.g4a7958ca14-goog
> >