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	Wed, 19 Nov 2025 01:14:47 +0000
Date: Wed, 19 Nov 2025 01:14:47 +0000
From: Al Viro <viro@zeniv.linux.org.uk>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org, torvalds@linux-foundation.org,
	brauner@kernel.org, jack@suse.cz, mjguzik@gmail.com,
	paul@paul-moore.com, audit@vger.kernel.org,
	io-uring@vger.kernel.org
Subject: Re: [RFC][PATCH 11/13] allow incomplete imports of filenames
Message-ID: <20251119011447.GM2441659@ZenIV>
References: <20251109063745.2089578-1-viro@zeniv.linux.org.uk>
 <20251109063745.2089578-12-viro@zeniv.linux.org.uk>
 <257804ed-438e-4085-a8c2-ac107fe4c73d@kernel.dk>
 <20251119011223.GL2441659@ZenIV>
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Sender: Al Viro <viro@ftp.linux.org.uk>

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.