Re: [RFC][PATCH 11/13] allow incomplete imports of filenames

[Al Viro <viro@zeniv.linux.org.uk>]

On Wed, Nov 19, 2025 at 01:14:47AM +0000, Al Viro wrote:
> On Wed, Nov 19, 2025 at 01:12:23AM +0000, Al Viro wrote:
> 
> > int putname_to_incomplete(struct incomplete_name *v, struct filename *name)
> > {
> > 	if (likely(name->refcnt == 1)) {
> > 		v->__incomplete_filename = name;
> > 		return 0;
> > 	}
> > 	v->__incomplete_filename = <duplicate name>;
> > 	putname(name);
> > 	if (unlikely(!v->__incomplete_filename))
> > 		return -ENOMEM;
> > 	return 0;
> > }
> > 
> > and have
> >                 if (ret == -EAGAIN &&
> > 		    (!resolve_nonblock && (issue_flags & IO_URING_F_NONBLOCK))) {
> > 			ret = putname_to_incomplete(&open->filename,
> > 						    no_free_ptr(name));
> > 			if (unlikely(ret))
> > 				goto err;
> > 			return -EAGAIN;
> > 		}
> > 
> > in io_openat2() (in addition to what's already done in 11/13).  Workable or
> > too disgusting?
> 
> Note that copying would happen only if extra references had been grabbed
> and are still held; that's already a slow path.

... and writing the "duplicate name" part has been a very convincing argument
in favour of a scheme Linus suggested upthread (shorter embedded name,
struct filename *always* coming from names_cachep, long name or short).
Current layout is too unpleasant to work with.