please, remove the abuse of vfs_path_lookup() in ecryptfs

please, remove the abuse of vfs_path_lookup() in ecryptfs

[Al Viro]

	commit 21edad32205e97dc7ccb81a85234c77e760364c8 (
ecryptfs: dont call lookup_one_len to avoid NULL nameidata) is badly
misguided.  The last thing we need is extra places where nameidata is
passed around.

	The current code is simply wrong - it's bypassing dcache
lookups in new_lower_dentry().  Besides, abuse of vfs_path_lookup()
here is a Bad Idea(tm).  No, filesystems are *not* allowed to die
if ->d_revalidate()/->lookup()/->create() are called with NULL
nameidata.  Eventually these methods will lose nameidata * anyway -
starting with ->d_revalidate() in the next cycle at the latest
(i.e. if we run into something really stinky in RCU mess, it might
happen before -final).

	Please revert that.

Re: please, remove the abuse of vfs_path_lookup() in ecryptfs

[Tyler Hicks]

On Thu Feb 17, 2011 at 01:53:50AM +0000, Al Viro <viro@ZenIV.linux.org.uk> wrote:
> 	commit 21edad32205e97dc7ccb81a85234c77e760364c8 (
> ecryptfs: dont call lookup_one_len to avoid NULL nameidata) is badly
> misguided.  The last thing we need is extra places where nameidata is
> passed around.

Thanks, Al. I reverted that patch and pushed it to
git://git.kernel.org/pub/scm/linux/kernel/git/ecryptfs/ecryptfs-2.6.git#next

I'll get a pull request together for Linus in the next day or two.

> 
> 	The current code is simply wrong - it's bypassing dcache
> lookups in new_lower_dentry().  Besides, abuse of vfs_path_lookup()
> here is a Bad Idea(tm).  No, filesystems are *not* allowed to die
> if ->d_revalidate()/->lookup()/->create() are called with NULL
> nameidata.

I fixed the eCryptfs d_revalidate, lookup, and create paths to not choke
when handed NULL nameidata. I don't think we would have ever received
NULL nameidata since we don't allow eCryptfs on eCryptfs or export to
NFS.

Tyler