[RFC PATCH v2 1/8] Use atomic type for ucounts reference counting

Alexey Gladkov
2021-01-10T17:42:50Z

include/linux/user_namespace.h | 2 +-
kernel/ucount.c | 10 +++++-----
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 64cf8ebdc4ec..84fefa9247c4 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;
+ atomic_t count;
atomic_t ucount[UCOUNT_COUNTS];
};

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 11b1596e2542..0f2c7c11df19 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;
+
+ atomic_set(&new->count, 0);

spin_lock_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
@@ -152,10 +153,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
ucounts = new;
}
}
- if (ucounts->count == INT_MAX)
+ if (atomic_read(&ucounts->count) == INT_MAX)
ucounts = NULL;
else
- ucounts->count += 1;
+ atomic_inc(&ucounts->count);
spin_unlock_irq(&ucounts_lock);
return ucounts;
}
@@ -165,8 +166,7 @@ static void put_ucounts(struct ucounts *ucounts)
unsigned long flags;

spin_lock_irqsave(&ucounts_lock, flags);
- ucounts->count -= 1;
- if (!ucounts->count)
+ if (atomic_dec_and_test(&ucounts->count))
hlist_del_init(&ucounts->node);
else
ucounts = NULL;