Re: VFS pathname walking cleanups (i_op and ACL access)

[Christoph Hellwig <hch@lst.de>]

On Fri, Jul 22, 2011 at 10:37:06AM -0700, Linus Torvalds wrote:
> The second patch moves the generic ACL caching case into the VFS layer the 
> way it should have been done a long time ago (we already moved the cache 
> fields into the core inode data structure), and just removes the need to 
> call into the filesystem for 'check_acl()' for the common cached case.

I've been wanting to that for a while and already had local patches for
it that needed forward porting.  I'll compare them with your version.

> 
> I don't expect this to be really at all controversial, but doing this, I 
> noticed that some of the ACL cache setup was a bit odd in filesystems. In 
> the case of XFS, for example, the test for
> 
> 	if (!XFS_IFORK_Q(ip))
> 		return -EAGAIN;
> 
> still remains in the filesystem-specific ACL check routine, which means 
> that since it doesn't show up in the cache, that case is now going to kick 
> XFS out of RCU. The fix seems to be trivial (just do a set_acl_cache() of 
> NULL for that case), but I didn't want to go into locking issues, so I 
> just added a comment.

It really just means we don't have an ACL.  I'll happily fix this in a
late merge window update.  We'll already need to do one as I have a few
small changes that should go in ontop of Jens' and Als trees.