[RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting

[Alexey Gladkov]

Signed-off-by: Alexey Gladkov <gladkov.ale...@gmail.com>
---
 include/linux/user_namespace.h |  2 +-
 kernel/ucount.c                | 20 +++++++-------------
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 64cf8ebdc4ec..f84fc2d9ce20 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -92,7 +92,7 @@ struct ucounts {
        struct hlist_node node;
        struct user_namespace *ns;
        kuid_t uid;
-       int count;
+       refcount_t count;
        atomic_t ucount[UCOUNT_COUNTS];
 };
 
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 11b1596e2542..82acd2226460 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -141,7 +141,8 @@ static struct ucounts *get_ucounts(struct user_namespace 
*ns, kuid_t uid)
 
                new->ns = ns;
                new->uid = uid;
-               new->count = 0;
+
+               refcount_set(&new->count, 0);
 
                spin_lock_irq(&ucounts_lock);
                ucounts = find_ucounts(ns, uid, hashent);
@@ -152,10 +153,7 @@ static struct ucounts *get_ucounts(struct user_namespace 
*ns, kuid_t uid)
                        ucounts = new;
                }
        }
-       if (ucounts->count == INT_MAX)
-               ucounts = NULL;
-       else
-               ucounts->count += 1;
+       refcount_inc(&ucounts->count);
        spin_unlock_irq(&ucounts_lock);
        return ucounts;
 }
@@ -164,15 +162,11 @@ static void put_ucounts(struct ucounts *ucounts)
 {
        unsigned long flags;
 
-       spin_lock_irqsave(&ucounts_lock, flags);
-       ucounts->count -= 1;
-       if (!ucounts->count)
+       if (refcount_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, 
&flags)) {
                hlist_del_init(&ucounts->node);
-       else
-               ucounts = NULL;
-       spin_unlock_irqrestore(&ucounts_lock, flags);
-
-       kfree(ucounts);
+               spin_unlock_irqrestore(&ucounts_lock, flags);
+               kfree(ucounts);
+       }
 }
 
 static inline bool atomic_inc_below(atomic_t *v, int u)
-- 
2.29.2