diff options
| -rw-r--r-- | kernel/acct.c | 85 |
1 files changed, 52 insertions, 33 deletions
diff --git a/kernel/acct.c b/kernel/acct.c index 21fbb3c27c2..6fd375f1562 100644 --- a/kernel/acct.c +++ b/kernel/acct.c @@ -79,9 +79,14 @@ int acct_parm[3] = {4, 2, 30}; static void do_acct_process(struct bsd_acct_struct *acct); struct bsd_acct_struct { - long count; - struct hlist_node s_list; - struct hlist_node m_list; + atomic_long_t count; + union { + struct { + struct hlist_node s_list; + struct hlist_node m_list; + }; + struct rcu_head rcu; + }; struct mutex lock; int active; unsigned long needcheck; @@ -89,6 +94,11 @@ struct bsd_acct_struct { struct pid_namespace *ns; }; +static void acct_free_rcu(struct rcu_head *head) +{ + kfree(container_of(head, struct bsd_acct_struct, rcu)); +} + static DEFINE_SPINLOCK(acct_lock); /* @@ -128,22 +138,22 @@ out: static void acct_put(struct bsd_acct_struct *p) { - spin_lock(&acct_lock); - if (!--p->count) - kfree(p); - spin_unlock(&acct_lock); + if (atomic_long_dec_and_test(&p->count)) + call_rcu(&p->rcu, acct_free_rcu); } static struct bsd_acct_struct *__acct_get(struct bsd_acct_struct *res) { - res->count++; - spin_unlock(&acct_lock); + if (!atomic_long_inc_not_zero(&res->count)) { + rcu_read_unlock(); + cpu_relax(); + return NULL; + } + rcu_read_unlock(); mutex_lock(&res->lock); if (!res->ns) { mutex_unlock(&res->lock); - spin_lock(&acct_lock); - if (!--res->count) - kfree(res); + acct_put(res); return NULL; } return res; @@ -152,13 +162,15 @@ static struct bsd_acct_struct *__acct_get(struct bsd_acct_struct *res) static struct bsd_acct_struct *acct_get(struct pid_namespace *ns) { struct bsd_acct_struct *res; - spin_lock(&acct_lock); again: - if (!ns->bacct) { - spin_unlock(&acct_lock); + smp_rmb(); + rcu_read_lock(); + res = ACCESS_ONCE(ns->bacct); + if (!res) { + rcu_read_unlock(); return NULL; } - res = __acct_get(ns->bacct); + res = __acct_get(res); if (!res) goto again; return res; @@ -170,26 +182,27 @@ static void acct_kill(struct bsd_acct_struct *acct, if (acct) { struct file *file = acct->file; struct pid_namespace *ns = acct->ns; + do_acct_process(acct); + mnt_unpin(file->f_path.mnt); + filp_close(file, NULL); spin_lock(&acct_lock); hlist_del(&acct->m_list); hlist_del(&acct->s_list); - mnt_unpin(file->f_path.mnt); spin_unlock(&acct_lock); - do_acct_process(acct); - filp_close(file, NULL); - spin_lock(&acct_lock); ns->bacct = new; if (new) { struct vfsmount *m = new->file->f_path.mnt; mnt_pin(m); + spin_lock(&acct_lock); hlist_add_head(&new->s_list, &m->mnt_sb->s_pins); hlist_add_head(&new->m_list, &real_mount(m)->mnt_pins); + spin_unlock(&acct_lock); + mutex_unlock(&new->lock); } acct->ns = NULL; + atomic_long_dec(&acct->count); mutex_unlock(&acct->lock); - if (!(acct->count -= 2)) - kfree(acct); - spin_unlock(&acct_lock); + acct_put(acct); } } @@ -223,7 +236,7 @@ static int acct_on(struct filename *pathname) return -EIO; } - acct->count = 1; + atomic_long_set(&acct->count, 1); acct->file = file; acct->needcheck = jiffies; acct->ns = ns; @@ -231,15 +244,17 @@ static int acct_on(struct filename *pathname) mnt = file->f_path.mnt; old = acct_get(ns); + mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */ if (old) { acct_kill(old, acct); } else { - spin_lock(&acct_lock); ns->bacct = acct; + spin_lock(&acct_lock); mnt_pin(mnt); hlist_add_head(&acct->s_list, &mnt->mnt_sb->s_pins); hlist_add_head(&acct->m_list, &real_mount(mnt)->mnt_pins); spin_unlock(&acct_lock); + mutex_unlock(&acct->lock); } mntput(mnt); /* it's pinned, now give up active reference */ return 0; @@ -282,28 +297,32 @@ SYSCALL_DEFINE1(acct, const char __user *, name) void acct_auto_close_mnt(struct hlist_head *list) { + rcu_read_lock(); while (1) { - spin_lock(&acct_lock); - if (!list->first) + struct hlist_node *p = ACCESS_ONCE(list->first); + if (!p) break; - acct_kill(__acct_get(hlist_entry(list->first, + acct_kill(__acct_get(hlist_entry(p, struct bsd_acct_struct, m_list)), NULL); + rcu_read_lock(); } - spin_unlock(&acct_lock); + rcu_read_unlock(); } void acct_auto_close(struct hlist_head *list) { + rcu_read_lock(); while (1) { - spin_lock(&acct_lock); - if (!list->first) + struct hlist_node *p = ACCESS_ONCE(list->first); + if (!p) break; - acct_kill(__acct_get(hlist_entry(list->first, + acct_kill(__acct_get(hlist_entry(p, struct bsd_acct_struct, s_list)), NULL); + rcu_read_lock(); } - spin_unlock(&acct_lock); + rcu_read_unlock(); } void acct_exit_ns(struct pid_namespace *ns) |