Re: [PATCH 33/36] tty/vt: consolemap: change refcount only if needed in con_do_clear_unimap()

Ilpo Järvinen
2022-06-07T15:49:32Z

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On Tue, 7 Jun 2022, Jiri Slaby wrote:

> con_do_clear_unimap() currently decreases and increases refcount of old
> dictionary in a back and forth fashion. This makes the code really hard
> to follow. Decrease the refcount only if everything went well and we
> really allocated a new one and decoupled from the old dictionary.
>
> I sincerelly hope I did not make a mistake in this (ill) logic.
>
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>

It seems fine:

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

One unrelated comment below for additional cleanup opportunity.

> ---
> drivers/tty/vt/consolemap.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> index 01b7e49f1f91..4d8efe74315c 100644
> --- a/drivers/tty/vt/consolemap.c
> +++ b/drivers/tty/vt/consolemap.c
> @@ -535,22 +535,23 @@ static int con_do_clear_unimap(struct vc_data *vc)
> {
> struct uni_pagedict *old = *vc->vc_uni_pagedir_loc;
>
> - if (!old || --old->refcount) {
> + if (!old || old->refcount > 1) {
> struct uni_pagedict *new = kzalloc(sizeof(*new), GFP_KERNEL);
> - if (!new) {
> - if (old)
> - old->refcount++;
> + if (!new)
> return -ENOMEM;
> - }
> +
> new->refcount = 1;
> *vc->vc_uni_pagedir_loc = new;
> +
> + if (old)
> + old->refcount--;
> } else {
> if (old == dflt)
> dflt = NULL;

This seems unnecessary as con_release_unimap() already does it.

> - old->refcount++;
> old->sum = 0;
> con_release_unimap(old);
> }
> +
> return 0;
> }
>
>

--
i.