On Wed, 2011-01-19 at 15:43 +0900, J. R. Okajima wrote:

Hi,

Nick Piggin:

quoted

Thanks for your help, can you see how I've fixed it in my vfs-scale
tree? What do you think?

Your fix is great. I have no objection at all.
Other than the fix, here are more generic questions about vfs-scale work.
I am happy if you reply when you have time.

- getcwd(2) needs d_lock?
  It acquires rename_lock and then tests whether the pwd is removed by
  d_unhashed(). If a race condition between vfs_rename_dir() which may
  unhash/rehash the dentry happens, then getcwd() may return the wrong
  result due to unprotected d_unhashed() call, I am afraid. rename_lock
  doesn't help this case.

- 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.

Ian


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