linux-kernel - Re: [PATCH v6 06/15] VFS: introduce start_creating_noperm() and start_removing

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Message-ID: <20251130001918.GM3538@ZenIV>
Date: Sun, 30 Nov 2025 00:19:18 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Val Packett <val@...kett.cool>
Cc: NeilBrown <neil@...wn.name>, Christian Brauner <brauner@...nel.org>,
	Amir Goldstein <amir73il@...il.com>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
	Chris Mason <clm@...com>, David Sterba <dsterba@...e.com>,
	David Howells <dhowells@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, Tyler Hicks <code@...icks.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	Chuck Lever <chuck.lever@...cle.com>,
	Olga Kornievskaia <okorniev@...hat.com>,
	Dai Ngo <Dai.Ngo@...cle.com>, Namjae Jeon <linkinjeon@...nel.org>,
	Steve French <smfrench@...il.com>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Carlos Maiolino <cem@...nel.org>,
	John Johansen <john.johansen@...onical.com>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Stephen Smalley <stephen.smalley.work@...il.com>,
	Ondrej Mosnacek <omosnace@...hat.com>,
	Mateusz Guzik <mjguzik@...il.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Stefan Berger <stefanb@...ux.ibm.com>,
	"Darrick J. Wong" <djwong@...nel.org>, linux-kernel@...r.kernel.org,
	netfs@...ts.linux.dev, ecryptfs@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-unionfs@...r.kernel.org,
	linux-cifs@...r.kernel.org, linux-xfs@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH v6 06/15] VFS: introduce start_creating_noperm() and
 start_removing_noperm()

On Sat, Nov 29, 2025 at 09:01:05PM -0300, Val Packett wrote:

> > diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> > index 316922d5dd13..a0d5b302bcc2 100644
> > --- a/fs/fuse/dir.c
> > +++ b/fs/fuse/dir.c
> > @@ -1397,27 +1397,25 @@ int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid,
> >   	if (!parent)
> >   		return -ENOENT;
> > -	inode_lock_nested(parent, I_MUTEX_PARENT);
> >   	if (!S_ISDIR(parent->i_mode))
> > -		goto unlock;
> > +		goto put_parent;
> >   	err = -ENOENT;
> >   	dir = d_find_alias(parent);
> >   	if (!dir)
> > -		goto unlock;
> > +		goto put_parent;
> > -	name->hash = full_name_hash(dir, name->name, name->len);
> > -	entry = d_lookup(dir, name);
> > +	entry = start_removing_noperm(dir, name);
> >   	dput(dir);
> > -	if (!entry)
> > -		goto unlock;
> > +	if (IS_ERR(entry))
> > +		goto put_parent;
> 
> This broke xdg-document-portal (and potentially other FUSE filesystems) by
> introducing a massive deadlock.

ACK.  That chunk needs to be reverted - this is *not* "remove an object by
parent and name", it's "invalidate stuff under that parent with this
first name component" and I would like to understand what FUSE_EXPIRE_ONLY
thing is about.

Miklos, could you give some details on that thing?  This chunk definitely
needs to go, the question is what that code is trying to do other than
d_invalidate()...