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Message-Id: <20251117-dir-deleg-ro-v7-1-f8bfd13a3791@kernel.org>
Date: Mon, 17 Nov 2025 08:27:11 -0500
From: Jeff Layton <jlayton@...nel.org>
To: 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>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v7] 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>
Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-17-52f3feebb2f2@kernel.org
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
Stephen hit a couple of problems while merging the last patch in the
directory delegation series. Christian, could you drop the last patch in
your vfs-6.19.directory.delegations branch and pick up this one instead?
I think it should address all of the problems he reported. Let me know
if you'd rather I resend the whole series.
Changes in v7:
- have fcntl.h include proper headers for stdint.h integers
- move comment above fcntl_getlease() to the proper place
- add a kerneldoc comment over fcntl_getdeleg()
---
fs/fcntl.c | 13 +++++++
fs/locks.c | 94 ++++++++++++++++++++++++++++++++++------------
include/linux/filelock.h | 12 ++++++
include/uapi/linux/fcntl.h | 16 ++++++++
4 files changed, 110 insertions(+), 25 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 72f8433d9109889eecef56b32d20a85b4e12ea44..f93dbca0843557d197bd1e023519cfa0f00ad78f 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 +551,18 @@ 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;
+ err = fcntl_getdeleg(filp, &deleg);
+ if (!err && copy_to_user(argp, &deleg, sizeof(deleg)))
+ return -EFAULT;
+ 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..3df07871b5ab7bbe883cdd8fba822d130282da8e 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1680,6 +1680,34 @@ void lease_get_mtime(struct inode *inode, struct timespec64 *time)
}
EXPORT_SYMBOL(lease_get_mtime);
+static int __fcntl_getlease(struct file *filp, unsigned int flavor)
+{
+ struct file_lease *fl;
+ struct inode *inode = file_inode(filp);
+ struct file_lock_context *ctx;
+ int type = F_UNLCK;
+ LIST_HEAD(dispose);
+
+ ctx = locks_inode_context(inode);
+ if (ctx && !list_empty_careful(&ctx->flc_lease)) {
+ percpu_down_read(&file_rwsem);
+ spin_lock(&ctx->flc_lock);
+ time_out_leases(inode, &dispose);
+ list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
+ if (fl->c.flc_file != filp)
+ continue;
+ if (fl->c.flc_flags & flavor)
+ type = target_leasetype(fl);
+ break;
+ }
+ spin_unlock(&ctx->flc_lock);
+ percpu_up_read(&file_rwsem);
+
+ locks_dispose_list(&dispose);
+ }
+ return type;
+}
+
/**
* fcntl_getlease - Enquire what lease is currently active
* @filp: the file
@@ -1705,29 +1733,24 @@ EXPORT_SYMBOL(lease_get_mtime);
*/
int fcntl_getlease(struct file *filp)
{
- struct file_lease *fl;
- struct inode *inode = file_inode(filp);
- struct file_lock_context *ctx;
- int type = F_UNLCK;
- LIST_HEAD(dispose);
-
- ctx = locks_inode_context(inode);
- if (ctx && !list_empty_careful(&ctx->flc_lease)) {
- percpu_down_read(&file_rwsem);
- spin_lock(&ctx->flc_lock);
- time_out_leases(inode, &dispose);
- list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
- if (fl->c.flc_file != filp)
- continue;
- type = target_leasetype(fl);
- break;
- }
- spin_unlock(&ctx->flc_lock);
- percpu_up_read(&file_rwsem);
+ return __fcntl_getlease(filp, FL_LEASE);
+}
- locks_dispose_list(&dispose);
- }
- return type;
+/**
+ * fcntl_getdeleg - enquire what sort of delegation is active
+ * @filp: file to be tested
+ * @deleg: structure where the result is stored
+ *
+ * Returns 0 on success or errno on failure. On success,
+ * deleg->d_type will contain the type of currently set lease
+ * (F_RDLCK, F_WRLCK or F_UNLCK).
+ */
+int fcntl_getdeleg(struct file *filp, struct delegation *deleg)
+{
+ if (deleg->d_flags != 0 || deleg->__pad != 0)
+ return -EINVAL;
+ deleg->d_type = __fcntl_getlease(filp, FL_DELEG);
+ return 0;
}
/**
@@ -2039,13 +2062,13 @@ 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 +2104,28 @@ 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 || deleg->__pad != 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..54b824c05299261e6bd6acc4175cb277ea35b35d 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, 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 -EINVAL;
+}
+
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..5e277fd955aae50fa59e93f23d462415ac0ca171 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -4,6 +4,11 @@
#include <asm/fcntl.h>
#include <linux/openat2.h>
+#ifdef __KERNEL__
+#include <linux/types.h>
+#else
+#include <stdint.h>
+#endif
#define F_SETLEASE (F_LINUX_SPECIFIC_BASE + 0)
#define F_GETLEASE (F_LINUX_SPECIFIC_BASE + 1)
@@ -79,6 +84,17 @@
*/
#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 {
+ uint32_t d_flags; /* Must be 0 */
+ uint16_t d_type; /* F_RDLCK, F_WRLCK, F_UNLCK */
+ uint16_t __pad; /* Must be 0 */
+};
+
/*
* Types of directory notifications that may be requested.
*/
---
base-commit: 8b99f6a8c116f664a6788737705f6da2772cc96a
change-id: 20251117-dir-deleg-ro-2e6247a1a0a9
Best regards,
--
Jeff Layton <jlayton@...nel.org>
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