Re: [PATCH] fs: handle shrinker registration failure in sget_userns

[Tetsuo Handa]

Jan Kara wrote:
> Looks good to me now. You can add:
> 
> Reviewed-by: Jan Kara <j...@suse.cz>
> 

It does not look good to me, for "goto fail" can call
destroy_unused_super() before s->s_shrink.list is initialized.
Also, the comment block saying "this object isn't exposed yet"
wants to be updated?

---
 fs/super.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 80b118c..44f0c6b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -197,6 +197,7 @@ static struct super_block *alloc_super(struct 
file_system_type *type, int flags,
        if (!s)
                return NULL;
 
+       INIT_LIST_HEAD(&s->s_shrink.list);
        INIT_LIST_HEAD(&s->s_mounts);
        s->s_user_ns = get_user_ns(user_ns);
 
@@ -260,9 +261,8 @@ static struct super_block *alloc_super(struct 
file_system_type *type, int flags,
        s->s_shrink.count_objects = super_cache_count;
        s->s_shrink.batch = 1024;
        s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
-       INIT_LIST_HEAD(&s->s_shrink.list);
-       return s;
-
+       if (register_shrinker(&s->s_shrink) == 0)
+               return s;
 fail:
        destroy_unused_super(s);
        return NULL;
@@ -512,10 +512,6 @@ struct super_block *sget_userns(struct file_system_type 
*type,
                s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
                if (!s)
                        return ERR_PTR(-ENOMEM);
-               if (register_shrinker(&s->s_shrink)) {
-                       destroy_unused_super(s);
-                       return ERR_PTR(-ENOMEM);
-               }
                goto retry;
        }
 
-- 
1.8.3.1