linux-kernel - Re: [PATCH RFC 06/24] vfs: break parent dir delegations in open(..., O

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Date: Mon, 18 Mar 2024 09:25:25 +0100
From: Stefan Metzmacher <metze@...ba.org>
To: Jeff Layton <jlayton@...nel.org>, Alexander Viro
 <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>,
 Jan Kara <jack@...e.cz>, Chuck Lever <chuck.lever@...cle.com>,
 Alexander Aring <alex.aring@...il.com>,
 Trond Myklebust <trond.myklebust@...merspace.com>,
 Anna Schumaker <anna@...nel.org>, Steve French <sfrench@...ba.org>,
 Paulo Alcantara <pc@...guebit.com>,
 Ronnie Sahlberg <ronniesahlberg@...il.com>,
 Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, David Howells
 <dhowells@...hat.com>, Tyler Hicks <code@...icks.com>,
 Neil Brown <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>,
 Dai Ngo <Dai.Ngo@...cle.com>, Miklos Szeredi <miklos@...redi.hu>,
 Amir Goldstein <amir73il@...il.com>, Namjae Jeon <linkinjeon@...nel.org>,
 Sergey Senozhatsky <senozhatsky@...omium.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
 samba-technical@...ts.samba.org, netfs@...ts.linux.dev,
 ecryptfs@...r.kernel.org, linux-unionfs@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH RFC 06/24] vfs: break parent dir delegations in open(...,
 O_CREAT) codepath

Hi Jeff,

> In order to add directory delegation support, we need to break
> delegations on the parent whenever there is going to be a change in the
> directory.
> 
> Add a delegated_inode parameter to lookup_open and have it break the
> delegation. Then, open_last_lookups can wait for the delegation break
> and retry the call to lookup_open once it's done.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
>   fs/namei.c | 22 ++++++++++++++++++----
>   1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index f00d8d708001..88598a62ec64 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3404,7 +3404,7 @@ static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
>    */
>   static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
>   				  const struct open_flags *op,
> -				  bool got_write)
> +				  bool got_write, struct inode **delegated_inode)

Does NFS has a concept of lease keys and parent lease keys?

In SMB it's possible that the client passes a lease key (16 client chosen bytes) to a directory open,
when asking for a directory lease.

Then operations on files within that directory, take that lease key from the directory as
'parent lease keys' in addition to a unique lease key for the file.

That way a client can avoid breaking its own directory leases when creating/move/delete... files
in the directory.

metze