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Message-Id: <20251103-dir-deleg-ro-v4-17-961b67adee89@kernel.org>
Date: Mon, 03 Nov 2025 07:52:45 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Miklos Szeredi <miklos@...redi.hu>,
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 <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>,
Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.org>,
Ronnie Sahlberg <ronniesahlberg@...il.com>,
Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
Bharath SM <bharathsm@...rosoft.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
David Howells <dhowells@...hat.com>, Tyler Hicks <code@...icks.com>,
NeilBrown <neil@...wn.name>, Olga Kornievskaia <okorniev@...hat.com>,
Dai Ngo <Dai.Ngo@...cle.com>, Amir Goldstein <amir73il@...il.com>,
Namjae Jeon <linkinjeon@...nel.org>, Steve French <smfrench@...il.com>,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Carlos Maiolino <cem@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>
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,
linux-xfs@...r.kernel.org, netdev@...r.kernel.org,
Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v4 17/17] vfs: expose delegation support to userland
Now that support for recallable directory delegations is available,
expose this functionality to userland with new F_SETDELEG and F_GETDELEG
commands for fcntl().
Note that this also allows userland to request a FL_DELEG type lease on
files too. Userland applications that do will get signalled when there
are metadata changes in addition to just data changes (which is a
limitation of FL_LEASE leases).
These commands accept a new "struct delegation" argument that contains a
flags field for future expansion.
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
fs/fcntl.c | 14 ++++++++++++++
fs/locks.c | 42 +++++++++++++++++++++++++++++++++++++-----
include/linux/filelock.h | 12 ++++++++++++
include/uapi/linux/fcntl.h | 10 ++++++++++
4 files changed, 73 insertions(+), 5 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 72f8433d9109889eecef56b32d20a85b4e12ea44..8d57a6e34076d68228b6d8d9bb381f78a751b151 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -445,6 +445,7 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
struct file *filp)
{
void __user *argp = (void __user *)arg;
+ struct delegation deleg;
int argi = (int)arg;
struct flock flock;
long err = -EINVAL;
@@ -550,6 +551,19 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
case F_SET_RW_HINT:
err = fcntl_set_rw_hint(filp, arg);
break;
+ case F_GETDELEG:
+ if (copy_from_user(&deleg, argp, sizeof(deleg)))
+ return -EFAULT;
+ fcntl_getdeleg(filp, &deleg);
+ if (copy_to_user(argp, &deleg, sizeof(deleg)))
+ return -EFAULT;
+ err = 0;
+ break;
+ case F_SETDELEG:
+ if (copy_from_user(&deleg, argp, sizeof(deleg)))
+ return -EFAULT;
+ err = fcntl_setdeleg(fd, filp, &deleg);
+ break;
default:
break;
}
diff --git a/fs/locks.c b/fs/locks.c
index dd290a87f58eb5d522f03fa99d612fbad84dacf3..1e29aecf79b8df66a6c67ca5f59cec40a376b9bc 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1703,7 +1703,7 @@ EXPORT_SYMBOL(lease_get_mtime);
* XXX: sfr & willy disagree over whether F_INPROGRESS
* should be returned to userspace.
*/
-int fcntl_getlease(struct file *filp)
+static int __fcntl_getlease(struct file *filp, unsigned int flavor)
{
struct file_lease *fl;
struct inode *inode = file_inode(filp);
@@ -1719,7 +1719,8 @@ int fcntl_getlease(struct file *filp)
list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
if (fl->c.flc_file != filp)
continue;
- type = target_leasetype(fl);
+ if (fl->c.flc_flags & flavor)
+ type = target_leasetype(fl);
break;
}
spin_unlock(&ctx->flc_lock);
@@ -1730,6 +1731,16 @@ int fcntl_getlease(struct file *filp)
return type;
}
+int fcntl_getlease(struct file *filp)
+{
+ return __fcntl_getlease(filp, FL_LEASE);
+}
+
+void fcntl_getdeleg(struct file *filp, struct delegation *deleg)
+{
+ deleg->d_type = __fcntl_getlease(filp, FL_DELEG);
+}
+
/**
* check_conflicting_open - see if the given file points to an inode that has
* an existing open that would conflict with the
@@ -2039,13 +2050,13 @@ vfs_setlease(struct file *filp, int arg, struct file_lease **lease, void **priv)
}
EXPORT_SYMBOL_GPL(vfs_setlease);
-static int do_fcntl_add_lease(unsigned int fd, struct file *filp, int arg)
+static int do_fcntl_add_lease(unsigned int fd, struct file *filp, unsigned int flavor, int arg)
{
struct file_lease *fl;
struct fasync_struct *new;
int error;
- fl = lease_alloc(filp, FL_LEASE, arg);
+ fl = lease_alloc(filp, flavor, arg);
if (IS_ERR(fl))
return PTR_ERR(fl);
@@ -2081,7 +2092,28 @@ int fcntl_setlease(unsigned int fd, struct file *filp, int arg)
if (arg == F_UNLCK)
return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
- return do_fcntl_add_lease(fd, filp, arg);
+ return do_fcntl_add_lease(fd, filp, FL_LEASE, arg);
+}
+
+/**
+ * fcntl_setdeleg - sets a delegation on an open file
+ * @fd: open file descriptor
+ * @filp: file pointer
+ * @deleg: delegation request from userland
+ *
+ * Call this fcntl to establish a delegation on the file.
+ * Note that you also need to call %F_SETSIG to
+ * receive a signal when the lease is broken.
+ */
+int fcntl_setdeleg(unsigned int fd, struct file *filp, struct delegation *deleg)
+{
+ /* For now, no flags are supported */
+ if (deleg->d_flags != 0)
+ return -EINVAL;
+
+ if (deleg->d_type == F_UNLCK)
+ return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
+ return do_fcntl_add_lease(fd, filp, FL_DELEG, deleg->d_type);
}
/**
diff --git a/include/linux/filelock.h b/include/linux/filelock.h
index 208d108df2d73a9df65e5dc9968d074af385f881..4384c6f61fad8f21d15974fac1d0f77747155f0f 100644
--- a/include/linux/filelock.h
+++ b/include/linux/filelock.h
@@ -159,6 +159,8 @@ int fcntl_setlk64(unsigned int, struct file *, unsigned int,
int fcntl_setlease(unsigned int fd, struct file *filp, int arg);
int fcntl_getlease(struct file *filp);
+int fcntl_setdeleg(unsigned int fd, struct file *filp, struct delegation *deleg);
+void fcntl_getdeleg(struct file *filp, struct delegation *deleg);
static inline bool lock_is_unlock(struct file_lock *fl)
{
@@ -278,6 +280,16 @@ static inline int fcntl_getlease(struct file *filp)
return F_UNLCK;
}
+static inline int fcntl_setdeleg(unsigned int fd, struct file *filp, struct delegation *deleg)
+{
+ return -EINVAL;
+}
+
+static inline int fcntl_getdeleg(struct file *filp, struct delegation *deleg)
+{
+ return F_UNLCK;
+}
+
static inline bool lock_is_unlock(struct file_lock *fl)
{
return false;
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 3741ea1b73d8500061567b6590ccf5fb4c6770f0..aae88f4b5c05205b2b28ae46b21bca9817197e04 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -79,6 +79,16 @@
*/
#define RWF_WRITE_LIFE_NOT_SET RWH_WRITE_LIFE_NOT_SET
+/* Set/Get delegations */
+#define F_GETDELEG (F_LINUX_SPECIFIC_BASE + 15)
+#define F_SETDELEG (F_LINUX_SPECIFIC_BASE + 16)
+
+/* Argument structure for F_GETDELEG and F_SETDELEG */
+struct delegation {
+ short d_type; /* F_RDLCK, F_WRLCK, F_UNLCK */
+ unsigned int d_flags;
+};
+
/*
* Types of directory notifications that may be requested.
*/
--
2.51.1
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