[linux-cifs-client] Re: lookup intent patch

[Jeff Layton]

On Mon, 30 Mar 2009 10:57:32 -0500
Shirish Pargaonkar <shirishpargaonkar at gmail.com> wrote:
> 
> Jeff,
> 
> Thanks.  Looking into it. I am trying to figure out the need/necessity
> for cifs_lookup to call lookup_instanitate_flip.
> lookup_instantiate_filp does call dentry_open and if cifs_lookup does
> not call lookup_instantiate_flip,
> nameidata_to_filp will call dentry_open.
> So I am not sure what we loose if dentry_open does not get called
> between lookup_hash and nameidata_to_flip
> because of an error between those two calls, specifically how will the
> cause of open file getting closed on the
> server will be served if there was an in-betwen error by calling
> lookup_instantiate_filp.
> 

I'm not certain since I haven't tested your patch, but you may end up
with an inode refcount leak (aka Busy inodes after umount...). You're
doing an open on the file in the lookup and I think that increases the
refcount of the inode (i_count). Eventually, that inode gets "put" when
you close the file. In the error situation described above though, that
put will never occur. As far as the VFS is concerned, the file was
never actually opened, so it doesn't need to issue a fput().

Properly cleaning up the references is the main reason to make sure
that you pass the filp back to the caller here. Closing the open file
on the server is also a nice side benefit since that could block the
granting of oplocks and such.

-- 
Jeff Layton <jlayton at redhat.com>