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

[Christoph Hellwig <hch@infradead.org>]

On Fri, Dec 09, 2005 at 08:33:45AM -0500, John T. Kohl wrote:
> Christoph> path_walk and firends resolve a full path.  As such they are
> Christoph> definitly not suitable for stackable filesystem, they are
> Christoph> intendeded only for implementating syscalls (and syscall-like
> Christoph> interfaces, e.g. some ioctls)
> 
> path_lookup() takes a pathname and interprets it relative to cwd or
> root, so it's definitely not useful for stacking.  But path_walk() takes
> a pathname fragment and an initialized nameidata (start point), so it
> *could* be used to resolve a single component, or multiple components.
> 
> If lookup_one_len() is for use within the caller's file system only, and
> path_walk() is not suitable for stacking, then what calls *are* suitable
> for stacking file systems to use?  We want to start with an existing
> (dentry,vfsmnt) and a pathname component, converting it to the
> (dentry,vfsmnt) of the result.

As there are no stackable filesystems in the tree there's currently no
interface designed for them, and once we'll get interfaces for stackable
filesystems they'll surely be _GPL as they're clearly internal and any
stackable filesystem needs to know a lot about the VFS and will have to
change far more frequently than leaf filesystems.

path_walk is an internal implementation detail that will hopefull go away
as an export.