linux-kernel - Re: [PATCH] fuse: fix conversion of fuse_reverse_inval_entry() to start

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Message-ID: <20251215-immens-hurtig-1f0b23aa4bf3@brauner>
Date: Mon, 15 Dec 2025 15:19:49 +0100
From: Christian Brauner <brauner@...nel.org>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: Al Viro <viro@...iv.linux.org.uk>, Amir Goldstein <amir73il@...il.com>, 
	NeilBrown <neil@...wn.name>, Val Packett <val@...kett.cool>, 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>, 
	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] fuse: fix conversion of fuse_reverse_inval_entry() to
 start_removing()

On Fri, Dec 05, 2025 at 02:09:41PM +0100, Christian Brauner wrote:
> On Mon, Dec 01, 2025 at 03:03:08PM +0100, Miklos Szeredi wrote:
> > On Mon, 1 Dec 2025 at 09:33, Al Viro <viro@...iv.linux.org.uk> wrote:
> > >
> > > On Mon, Dec 01, 2025 at 09:22:54AM +0100, Amir Goldstein wrote:
> > >
> > > > I don't think there is a point in optimizing parallel dir operations
> > > > with FUSE server cache invalidation, but maybe I am missing
> > > > something.
> > >
> > > The interesting part is the expected semantics of operation;
> > > d_invalidate() side definitely doesn't need any of that cruft,
> > > but I would really like to understand what that function
> > > is supposed to do.
> > >
> > > Miklos, could you post a brain dump on that?
> > 
> > This function is supposed to invalidate a dentry due to remote changes
> > (FUSE_NOTIFY_INVAL_ENTRY).  Originally it was supplied a parent ID and
> > a name and called d_invalidate() on the looked up dentry.
> > 
> > Then it grew a variant (FUSE_NOTIFY_DELETE) that was also supplied a
> > child ID, which was matched against the looked up inode.  This was
> > commit 451d0f599934 ("FUSE: Notifying the kernel of deletion."),
> > Apparently this worked around the fact that at that time
> > d_invalidate() returned -EBUSY if the target was still in use and
> > didn't unhash the dentry in that case.
> > 
> > That was later changed by commit bafc9b754f75 ("vfs: More precise
> > tests in d_invalidate") to unconditionally unhash the target, which
> > effectively made FUSE_NOTIFY_INVAL_ENTRY and FUSE_NOTIFY_DELETE
> > equivalent and the code in question unnecessary.
> > 
> > For the future, we could also introduce FUSE_NOTIFY_MOVE, that would
> > differentiate between a delete and a move, while
> > FUSE_NOTIFY_INVAL_ENTRY would continue to be the common (deleted or
> > moved) notification.
> > 
> > Attaching untested patch to remove this cruft.
> 
> Should we revert the fuse specific bits of c9ba789dad15 ("VFS: introduce
> start_creating_noperm() and start_removing_noperm()") and then apply
> your changes afterwards?

I think we shouldn't have this sitting around indefinitely so it would
be good if we'd get a nod that this is ok or someone sending revert +
fix that I can pick up. :)