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From: Jeff Layton <jlayton@kernel.org>
Date: Fri, 15 Mar 2024 12:52:53 -0400
Subject: [PATCH RFC 02/24] filelock: add a lm_set_conflict lease_manager
 callback
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Message-Id: <20240315-dir-deleg-v1-2-a1d6209a3654@kernel.org>
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To: Alexander Viro <viro@zeniv.linux.org.uk>, 
 Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>, 
 Chuck Lever <chuck.lever@oracle.com>, 
 Alexander Aring <alex.aring@gmail.com>, 
 Trond Myklebust <trond.myklebust@hammerspace.com>, 
 Anna Schumaker <anna@kernel.org>, Steve French <sfrench@samba.org>, 
 Paulo Alcantara <pc@manguebit.com>, 
 Ronnie Sahlberg <ronniesahlberg@gmail.com>, 
 Shyam Prasad N <sprasad@microsoft.com>, Tom Talpey <tom@talpey.com>, 
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@kernel.org>, 
 David Howells <dhowells@redhat.com>, Tyler Hicks <code@tyhicks.com>, 
 Neil Brown <neilb@suse.de>, Olga Kornievskaia <kolga@netapp.com>, 
 Dai Ngo <Dai.Ngo@oracle.com>, Miklos Szeredi <miklos@szeredi.hu>, 
 Amir Goldstein <amir73il@gmail.com>, Namjae Jeon <linkinjeon@kernel.org>, 
 Sergey Senozhatsky <senozhatsky@chromium.org>, 
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, 
 Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, 
 linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, 
 samba-technical@lists.samba.org, netfs@lists.linux.dev, 
 ecryptfs@vger.kernel.org, linux-unionfs@vger.kernel.org, 
 netdev@vger.kernel.org, Jeff Layton <jlayton@kernel.org>

The NFSv4.1 protocol adds support for directory delegations, but it
specifies that if you already have a delegation and try to request a new
one on the same filehandle, the server must reply that the delegation is
unavailable.

Add a new lease_manager callback to allow the lease manager (nfsd in
this case) to impose extra checks when performing a setlease.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/locks.c               |  5 +++++
 include/linux/filelock.h | 10 ++++++++++
 2 files changed, 15 insertions(+)

diff --git a/fs/locks.c b/fs/locks.c
index cb4b35d26162..415cca8e9565 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1822,6 +1822,11 @@ generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **pr
 			continue;
 		}
 
+		/* Allow the lease manager to veto the setlease */
+		if (lease->fl_lmops->lm_set_conflict &&
+		    lease->fl_lmops->lm_set_conflict(lease, fl))
+			goto out;
+
 		/*
 		 * No exclusive leases if someone else has a lease on
 		 * this file:
diff --git a/include/linux/filelock.h b/include/linux/filelock.h
index daee999d05f3..c5fc768087df 100644
--- a/include/linux/filelock.h
+++ b/include/linux/filelock.h
@@ -49,6 +49,16 @@ struct lease_manager_operations {
 	int (*lm_change)(struct file_lease *, int, struct list_head *);
 	void (*lm_setup)(struct file_lease *, void **);
 	bool (*lm_breaker_owns_lease)(struct file_lease *);
+
+	/**
+	 * lm_set_conflict - extra conditions for setlease
+	 * @new: new file_lease being set
+	 * @old: old (extant) file_lease
+	 *
+	 * This allows the lease manager to add extra conditions when
+	 * setting a lease.
+	 */
+	bool (*lm_set_conflict)(struct file_lease *new, struct file_lease *old);
 };
 
 struct lock_manager {

-- 
2.44.0