[bug report] mm: shrinker: add a secondary array for shrinker_info::{map, nr_deferred}

[Dan Carpenter <dan.carpenter@linaro.org>]

Hello Qi Zheng,

The patch b6884b5f15cf: "mm: shrinker: add a secondary array for
shrinker_info::{map, nr_deferred}" from Sep 11, 2023 (linux-next),
leads to the following Smatch static checker warning:

	mm/shrinker.c:100 alloc_shrinker_info()
	warn: inconsistent returns '&shrinker_mutex'.

mm/shrinker.c
    77 int alloc_shrinker_info(struct mem_cgroup *memcg)
    78 {
    79         struct shrinker_info *info;
    80         int nid, ret = 0;
    81         int array_size = 0;
    82 
    83         mutex_lock(&shrinker_mutex);
    84         array_size = shrinker_unit_size(shrinker_nr_max);
    85         for_each_node(nid) {
    86                 info = kvzalloc_node(sizeof(*info) + array_size, GFP_KERNEL, nid);
    87                 if (!info)
    88                         goto err;
                               ^^^^^^^^^

    89                 info->map_nr_max = shrinker_nr_max;
    90                 if (shrinker_unit_alloc(info, NULL, nid))
    91                         goto err;
                               ^^^^^^^^
These error paths need to unlock.  I'm not 100% positive if you want to
unlock before or after the call to free_shrinker_info().

    92                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
    93         }
    94         mutex_unlock(&shrinker_mutex);
    95 
    96         return ret;
    97 
    98 err:
    99         free_shrinker_info(memcg);
-->100         return -ENOMEM;
   101 }

regards,
dan carpenter