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new fs_pin killing logics

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2015-01-10 17:53:21 -05:00
parent fdab684d72
commit 59eda0e07f
4 changed files with 96 additions and 56 deletions
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81
kernel/acct.c
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@@ -76,7 +76,6 @@ 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;
@@ -91,6 +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.
*/
@@ -132,13 +133,18 @@ static void acct_put(struct bsd_acct_struct *p)
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;
@@ -150,7 +156,7 @@ again:
}
rcu_read_unlock();
mutex_lock(&res->lock);
if (!res->ns) {
if (res != to_acct(ACCESS_ONCE(ns->bacct))) {
mutex_unlock(&res->lock);
acct_put(res);
goto again;
@@ -158,6 +164,19 @@ 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);
@@ -168,49 +187,13 @@ static void close_work(struct work_struct *work)
complete(&acct->done);
}
static void acct_kill(struct bsd_acct_struct *acct)
{
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);
cmpxchg(&ns->bacct, acct, NULL);
acct->ns = NULL;
atomic_long_dec(&acct->count);
mutex_unlock(&acct->lock);
acct_put(acct);
}
}
static void acct_pin_kill(struct fs_pin *pin)
{
struct bsd_acct_struct *acct;
acct = container_of(pin, struct bsd_acct_struct, pin);
if (!atomic_long_inc_not_zero(&acct->count)) {
rcu_read_unlock();
cpu_relax();
return;
}
rcu_read_unlock();
mutex_lock(&acct->lock);
if (!acct->ns) {
mutex_unlock(&acct->lock);
acct_put(acct);
acct = NULL;
}
acct_kill(acct);
}
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);
@@ -252,18 +235,20 @@ static int acct_on(struct filename *pathname)
file->f_path.mnt = internal;
atomic_long_set(&acct->count, 1);
acct->pin.kill = acct_pin_kill;
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);
ns->bacct = acct;
acct_kill(old);
rcu_read_lock();
old = xchg(&ns->bacct, &acct->pin);
mutex_unlock(&acct->lock);
pin_kill(old);
mnt_drop_write(mnt);
mntput(mnt);
return 0;
@@ -299,7 +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)));
rcu_read_lock();
pin_kill(task_active_pid_ns(current)->bacct);
}
return error;
@@ -307,7 +293,8 @@ SYSCALL_DEFINE1(acct, const char __user *, name)
void acct_exit_ns(struct pid_namespace *ns)
{
acct_kill(acct_get(ns));
rcu_read_lock();
pin_kill(ns->bacct);
}
/*