Oleg Nesterov wrote:
On 07/26, Pavel Emelyanov wrote:
static int proc_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
[...snip...]
+ if (!sb->s_root) {
+ sb->s_flags = flags;
+ err = proc_fill_super(sb);
+ if (err) {
+ up_write(&sb->s_umount);
+ deactivate_super(sb);
+ return err;
+ }
+
+ ei = PROC_I(sb->s_root->d_inode);
+ if (!ei->pid) {
+ rcu_read_lock();
+ ei->pid = get_pid(find_pid_ns(1, ns));
Where do we "put" this pid?
In proc_delete_inode()
void release_task(struct task_struct * p)
{
+ struct pid *pid;
struct task_struct *leader;
int zap_leader;
repeat:
@@ -160,6 +161,20 @@ repeat:
write_lock_irq(&tasklist_lock);
ptrace_unlink(p);
BUG_ON(!list_empty(&p->ptrace_list) ||
!list_empty(&p->ptrace_children));
+ /*
+ * we have to keep this pid till proc_flush_task() to make
+ * it possible to flush all dentries holding it. pid will
+ * be put ibidem
+ *
+ * however if the pid belogs to init namespace only, we can
+ * optimize this out
+ */
+ pid = task_pid(p);
+ if (pid->level != 0)
+ get_pid(pid);
+ else
+ pid = NULL;
+
__exit_signal(p);
/*
@@ -184,7 +199,8 @@ repeat:
}
write_unlock_irq(&tasklist_lock);
- proc_flush_task(p, NULL);
+ proc_flush_task(p, pid);
+ put_pid(pid);
Oh, this is not nice...
Look, proc_flush_task() doesn't need pid, it can use active pid_ns
It cannot. By the time release_task() is called the task is already
exit_task_namespaces()-ed :(
to iterate the ->parent chain and do proc_flush_task_mnt(), and it
can check "ns->child_reaper == current" for mntput(), yes?
So, can't we do instead
release_task()
{
struct pid_namespace *my_ns = ...; // get it from pid;
So, that's what you mean. Well, that's sounds reasonable. Thanks.
...
write_unlock_irq(&tasklist_lock);
// __exit_signal()->...->put_pid() drops the reference,
// but this ns should still be valid because /proc itself
// holds a reference to it, even if we are /sbin/init.
proc_flush_task(p, my_ns);
...
}
No?
Yes. Thanks!
Oleg.
Pavel
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