Re: [autofs] [RFC PATCH]autofs4: hang and proposed fix

["William H. Taber" <wtaber@us.ibm.com>]

Ram Pai wrote:
> On Fri, 2005-11-18 at 09:12, William H. Taber wrote:

> 
> I think the problem is with cached_lookup(). It is the only place which 
> calls ->revalidate() holding the parent's inode-semaphore AFAICT.
> 
> note: cached_lookup() is only called from __lookup_hash() and
> __lookup_hash() is always called holding the semaphore.
> 
> VFS experts agree?
> RP
> 
Ram,
Lookup_one_len calls lookup_hash and it is the callers of lookup_one_len 
that are problematical.  Just as an example, lookup_one_len is called 
from nfs_sillyrename which is called, among other places in the 
nfs_rename code.  In that path the parent i_sem is obtained in do_rename 
   in the vfs code (namei.c). I would think that it would be extremely 
difficult to to change that usage.  The alternative is to move the 
obtaining of the parent i_sem from real_lookup to do_lookup.  We would 
also have to put the locking around the d_revalidate call at 
return_reval in __link_path_walk.

Again, what do the VFS experts think?

Will Taber