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

[Brian Geffon <bgeffon@google.com>]

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()?

>
> 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
>