Merge tag 'fbdev-fixes-4.0' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba...

[linux-drm-fsl-dcu.git] / kernel / acct.c

diff --git a/kernel/acct.c b/kernel/acct.c
index 33738ef972f3b917f0820e3c751978e7956b1d4a..e6c10d1a405821d55b7595a2cd5e3404766d3d42 100644 (file)
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -76,10 +76,11 @@ int acct_parm[3] = {4, 2, 30};
 /*
  * External references and all of the globals.
  */
-static void do_acct_process(struct bsd_acct_struct *acct);
 
 struct bsd_acct_struct {
        struct fs_pin           pin;
+       atomic_long_t           count;
+       struct rcu_head         rcu;
        struct mutex            lock;
        int                     active;
        unsigned long           needcheck;
@@ -89,6 +90,8 @@ struct bsd_acct_struct {
        struct completion       done;
 };
 
+static void do_acct_process(struct bsd_acct_struct *acct);
+
 /*
  * Check the amount of free space and suspend/resume accordingly.
  */
@@ -124,32 +127,56 @@ out:
        return acct->active;
 }
 
+static void acct_put(struct bsd_acct_struct *p)
+{
+       if (atomic_long_dec_and_test(&p->count))
+               kfree_rcu(p, rcu);
+}
+
+static inline struct bsd_acct_struct *to_acct(struct fs_pin *p)
+{
+       return p ? container_of(p, struct bsd_acct_struct, pin) : NULL;
+}
+
 static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
 {
        struct bsd_acct_struct *res;
 again:
        smp_rmb();
        rcu_read_lock();
-       res = ACCESS_ONCE(ns->bacct);
+       res = to_acct(ACCESS_ONCE(ns->bacct));
        if (!res) {
                rcu_read_unlock();
                return NULL;
        }
-       if (!atomic_long_inc_not_zero(&res->pin.count)) {
+       if (!atomic_long_inc_not_zero(&res->count)) {
                rcu_read_unlock();
                cpu_relax();
                goto again;
        }
        rcu_read_unlock();
        mutex_lock(&res->lock);
-       if (!res->ns) {
+       if (res != to_acct(ACCESS_ONCE(ns->bacct))) {
                mutex_unlock(&res->lock);
-               pin_put(&res->pin);
+               acct_put(res);
                goto again;
        }
        return res;
 }
 
+static void acct_pin_kill(struct fs_pin *pin)
+{
+       struct bsd_acct_struct *acct = to_acct(pin);
+       mutex_lock(&acct->lock);
+       do_acct_process(acct);
+       schedule_work(&acct->work);
+       wait_for_completion(&acct->done);
+       cmpxchg(&acct->ns->bacct, pin, NULL);
+       mutex_unlock(&acct->lock);
+       pin_remove(pin);
+       acct_put(acct);
+}
+
 static void close_work(struct work_struct *work)
 {
        struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
@@ -160,44 +187,13 @@ static void close_work(struct work_struct *work)
        complete(&acct->done);
 }
 
-static void acct_kill(struct bsd_acct_struct *acct,
-                     struct bsd_acct_struct *new)
-{
-       if (acct) {
-               struct pid_namespace *ns = acct->ns;
-               do_acct_process(acct);
-               INIT_WORK(&acct->work, close_work);
-               init_completion(&acct->done);
-               schedule_work(&acct->work);
-               wait_for_completion(&acct->done);
-               pin_remove(&acct->pin);
-               ns->bacct = new;
-               acct->ns = NULL;
-               atomic_long_dec(&acct->pin.count);
-               mutex_unlock(&acct->lock);
-               pin_put(&acct->pin);
-       }
-}
-
-static void acct_pin_kill(struct fs_pin *pin)
-{
-       struct bsd_acct_struct *acct;
-       acct = container_of(pin, struct bsd_acct_struct, pin);
-       mutex_lock(&acct->lock);
-       if (!acct->ns) {
-               mutex_unlock(&acct->lock);
-               pin_put(pin);
-               acct = NULL;
-       }
-       acct_kill(acct, NULL);
-}
-
 static int acct_on(struct filename *pathname)
 {
        struct file *file;
        struct vfsmount *mnt, *internal;
        struct pid_namespace *ns = task_active_pid_ns(current);
-       struct bsd_acct_struct *acct, *old;
+       struct bsd_acct_struct *acct;
+       struct fs_pin *old;
        int err;
 
        acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
@@ -238,21 +234,21 @@ static int acct_on(struct filename *pathname)
        mnt = file->f_path.mnt;
        file->f_path.mnt = internal;
 
-       atomic_long_set(&acct->pin.count, 1);
-       acct->pin.kill = acct_pin_kill;
+       atomic_long_set(&acct->count, 1);
+       init_fs_pin(&acct->pin, acct_pin_kill);
        acct->file = file;
        acct->needcheck = jiffies;
        acct->ns = ns;
        mutex_init(&acct->lock);
+       INIT_WORK(&acct->work, close_work);
+       init_completion(&acct->done);
        mutex_lock_nested(&acct->lock, 1);      /* nobody has seen it yet */
        pin_insert(&acct->pin, mnt);
 
-       old = acct_get(ns);
-       if (old)
-               acct_kill(old, acct);
-       else
-               ns->bacct = acct;
+       rcu_read_lock();
+       old = xchg(&ns->bacct, &acct->pin);
        mutex_unlock(&acct->lock);
+       pin_kill(old);
        mnt_drop_write(mnt);
        mntput(mnt);
        return 0;
@@ -288,7 +284,8 @@ SYSCALL_DEFINE1(acct, const char __user *, name)
                mutex_unlock(&acct_on_mutex);
                putname(tmp);
        } else {
-               acct_kill(acct_get(task_active_pid_ns(current)), NULL);
+               rcu_read_lock();
+               pin_kill(task_active_pid_ns(current)->bacct);
        }
 
        return error;
@@ -296,7 +293,8 @@ SYSCALL_DEFINE1(acct, const char __user *, name)
 
 void acct_exit_ns(struct pid_namespace *ns)
 {
-       acct_kill(acct_get(ns), NULL);
+       rcu_read_lock();
+       pin_kill(ns->bacct);
 }
 
 /*
@@ -576,7 +574,7 @@ static void slow_acct_process(struct pid_namespace *ns)
                if (acct) {
                        do_acct_process(acct);
                        mutex_unlock(&acct->lock);
-                       pin_put(&acct->pin);
+                       acct_put(acct);
                }
        }
 }