tty/vt: consolemap: change refcount only if needed in con_do_clear_unimap()

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.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-33-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
index 01b7e49f1f913329c776865a5f9ed7186c6e1c56..4d8efe74315c2adb256241492b6293e841d614ee 100644 (file)
--- 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;
-               old->refcount++;
                old->sum = 0;
                con_release_unimap(old);
        }
+
        return 0;
 }