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Message-Id: <20251021-dir-deleg-ro-v3-13-a08b1cde9f4c@kernel.org>
Date: Tue, 21 Oct 2025 11:25:48 -0400
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 v3 13/13] vfs: expose delegation support to userland
Now that support for recallable directory delegations is complete,
expose this functionality to userland with new F_SETDELEG and F_GETDELEG
commands for fcntl(). 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 | 9 ++++++++
fs/locks.c | 53 ++++++++++++++++++++++++++++++++++++----------
include/linux/filelock.h | 12 +++++++++++
include/uapi/linux/fcntl.h | 10 +++++++++
4 files changed, 73 insertions(+), 11 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 72f8433d9109889eecef56b32d20a85b4e12ea44..f34f0a07f993f9f95a60f2954bb4304d3c218498 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 +551,14 @@ 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:
+ err = fcntl_getdeleg(filp);
+ 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 b47552106769ec5a189babfe12518e34aa59c759..fda62897e371fbc8d04b8073df3d2267d2c7c430 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -585,7 +585,7 @@ static const struct lease_manager_operations lease_manager_ops = {
/*
* Initialize a lease, use the default lock manager operations
*/
-static int lease_init(struct file *filp, int type, struct file_lease *fl)
+static int lease_init(struct file *filp, unsigned int flags, int type, struct file_lease *fl)
{
if (assign_type(&fl->c, type) != 0)
return -EINVAL;
@@ -594,13 +594,13 @@ static int lease_init(struct file *filp, int type, struct file_lease *fl)
fl->c.flc_pid = current->tgid;
fl->c.flc_file = filp;
- fl->c.flc_flags = FL_LEASE;
+ fl->c.flc_flags = flags;
fl->fl_lmops = &lease_manager_ops;
return 0;
}
/* Allocate a file_lock initialised to this type of lease */
-static struct file_lease *lease_alloc(struct file *filp, int type)
+static struct file_lease *lease_alloc(struct file *filp, unsigned int flags, int type)
{
struct file_lease *fl = locks_alloc_lease();
int error = -ENOMEM;
@@ -608,7 +608,7 @@ static struct file_lease *lease_alloc(struct file *filp, int type)
if (fl == NULL)
return ERR_PTR(error);
- error = lease_init(filp, type, fl);
+ error = lease_init(filp, flags, type, fl);
if (error) {
locks_free_lease(fl);
return ERR_PTR(error);
@@ -1548,10 +1548,9 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
int want_write = (mode & O_ACCMODE) != O_RDONLY;
LIST_HEAD(dispose);
- new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
+ new_fl = lease_alloc(NULL, type, want_write ? F_WRLCK : F_RDLCK);
if (IS_ERR(new_fl))
return PTR_ERR(new_fl);
- new_fl->c.flc_flags = type;
/* typically we will check that ctx is non-NULL before calling */
ctx = locks_inode_context(inode);
@@ -1697,7 +1696,7 @@ 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);
@@ -1713,7 +1712,8 @@ 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);
@@ -1724,6 +1724,16 @@ int fcntl_getlease(struct file *filp)
return type;
}
+int fcntl_getlease(struct file *filp)
+{
+ return __fcntl_getlease(filp, FL_LEASE);
+}
+
+int fcntl_getdeleg(struct file *filp)
+{
+ return __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
@@ -2033,13 +2043,13 @@ 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, arg);
+ fl = lease_alloc(filp, flavor, arg);
if (IS_ERR(fl))
return PTR_ERR(fl);
@@ -2075,7 +2085,28 @@ 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 c2ce8ba05d068b451ecf8f513b7e532819a29944..69b8fa8dce35dab670e6c7b288e13dc4caed1bc0 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);
+int fcntl_getdeleg(struct file *filp);
static inline bool lock_is_unlock(struct file_lock *fl)
{
@@ -271,6 +273,16 @@ 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)
+{
+ 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.
*/
--
2.51.0
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