Ian Kent:

quoted

- what is the right order of dget() and mntget()?
  If I remember correctly, someone said "mntget() first and then
  dget(). when putting, do in reverse" in the discussion when
  path_{get,put}() were born. So it is called "the right order" in the
  commit log.
  It was many years ago. Is it still true? And should rcu-walk follow it
  too? The current implementation doesn't seem to care about this order.

I didn't spot that, where did you see this?

I'm not sure about the get but I fairly sure the dput() has to be before
the mntput() because the shrink_dcache_*() cleanup routines object to
dentrys that have a reference count of more than one.

For dget - mntget, there are several such code. For example,
nameidata_dentry_drop_rcu()
{
	struct dentry *parent = nd->path.dentry;
		:::
	parent->d_count++;
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
		:::
	mntget(nd->path.mnt);
		:::

But I am not sure the "get" order is a problem.
Nick Piggin also replied and said dget and mntget is not a problem, and
I replied if I found such "put" order, I would write again.


J. R. Okajima