* [PATCH v8 1/3] vfs: expose delegation support to userland
2025-11-19 13:42 [PATCH v8 0/3] vfs: expose delegation support to userland Jeff Layton
@ 2025-11-19 13:42 ` Jeff Layton
2025-11-19 13:42 ` [PATCH v8 2/3] filelock: add lease_dispose_list() helper Jeff Layton
2025-11-19 13:42 ` [PATCH v8 3/3] filelock: allow lease_managers to dictate what qualifies as a conflict Jeff Layton
2 siblings, 0 replies; 4+ messages in thread
From: Jeff Layton @ 2025-11-19 13:42 UTC (permalink / raw)
To: Alexander Viro, Christian Brauner, Jan Kara, Jeff Layton,
Chuck Lever, Alexander Aring, NeilBrown, Olga Kornievskaia,
Dai Ngo, Tom Talpey
Cc: linux-fsdevel, linux-kernel, linux-nfs, Stephen Rothwell
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@kernel.org>
Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-17-52f3feebb2f2@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
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.
*/
--
2.51.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v8 2/3] filelock: add lease_dispose_list() helper
2025-11-19 13:42 [PATCH v8 0/3] vfs: expose delegation support to userland Jeff Layton
2025-11-19 13:42 ` [PATCH v8 1/3] " Jeff Layton
@ 2025-11-19 13:42 ` Jeff Layton
2025-11-19 13:42 ` [PATCH v8 3/3] filelock: allow lease_managers to dictate what qualifies as a conflict Jeff Layton
2 siblings, 0 replies; 4+ messages in thread
From: Jeff Layton @ 2025-11-19 13:42 UTC (permalink / raw)
To: Alexander Viro, Christian Brauner, Jan Kara, Jeff Layton,
Chuck Lever, Alexander Aring, NeilBrown, Olga Kornievskaia,
Dai Ngo, Tom Talpey
Cc: linux-fsdevel, linux-kernel, linux-nfs, Stephen Rothwell
...and call that from the lease handling code instead of
locks_dispose_list(). Remove the lease handling parts from
locks_dispose_list().
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/locks.c | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index 3df07871b5ab7bbe883cdd8fba822d130282da8e..d4e6af6ac625204b337e94fd1e4f6df2eee5cf50 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -369,10 +369,19 @@ locks_dispose_list(struct list_head *dispose)
while (!list_empty(dispose)) {
flc = list_first_entry(dispose, struct file_lock_core, flc_list);
list_del_init(&flc->flc_list);
- if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
- locks_free_lease(file_lease(flc));
- else
- locks_free_lock(file_lock(flc));
+ locks_free_lock(file_lock(flc));
+ }
+}
+
+static void
+lease_dispose_list(struct list_head *dispose)
+{
+ struct file_lock_core *flc;
+
+ while (!list_empty(dispose)) {
+ flc = list_first_entry(dispose, struct file_lock_core, flc_list);
+ list_del_init(&flc->flc_list);
+ locks_free_lease(file_lease(flc));
}
}
@@ -1620,7 +1629,7 @@ int __break_lease(struct inode *inode, unsigned int flags)
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
- locks_dispose_list(&dispose);
+ lease_dispose_list(&dispose);
error = wait_event_interruptible_timeout(new_fl->c.flc_wait,
list_empty(&new_fl->c.flc_blocked_member),
break_time);
@@ -1643,7 +1652,7 @@ int __break_lease(struct inode *inode, unsigned int flags)
out:
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
- locks_dispose_list(&dispose);
+ lease_dispose_list(&dispose);
free_lock:
locks_free_lease(new_fl);
return error;
@@ -1703,7 +1712,7 @@ static int __fcntl_getlease(struct file *filp, unsigned int flavor)
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
- locks_dispose_list(&dispose);
+ lease_dispose_list(&dispose);
}
return type;
}
@@ -1904,7 +1913,7 @@ generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **pr
out:
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
- locks_dispose_list(&dispose);
+ lease_dispose_list(&dispose);
if (is_deleg)
inode_unlock(inode);
if (!error && !my_fl)
@@ -1940,7 +1949,7 @@ static int generic_delete_lease(struct file *filp, void *owner)
error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
- locks_dispose_list(&dispose);
+ lease_dispose_list(&dispose);
return error;
}
@@ -2735,7 +2744,7 @@ locks_remove_lease(struct file *filp, struct file_lock_context *ctx)
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
- locks_dispose_list(&dispose);
+ lease_dispose_list(&dispose);
}
/*
--
2.51.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v8 3/3] filelock: allow lease_managers to dictate what qualifies as a conflict
2025-11-19 13:42 [PATCH v8 0/3] vfs: expose delegation support to userland Jeff Layton
2025-11-19 13:42 ` [PATCH v8 1/3] " Jeff Layton
2025-11-19 13:42 ` [PATCH v8 2/3] filelock: add lease_dispose_list() helper Jeff Layton
@ 2025-11-19 13:42 ` Jeff Layton
2 siblings, 0 replies; 4+ messages in thread
From: Jeff Layton @ 2025-11-19 13:42 UTC (permalink / raw)
To: Alexander Viro, Christian Brauner, Jan Kara, Jeff Layton,
Chuck Lever, Alexander Aring, NeilBrown, Olga Kornievskaia,
Dai Ngo, Tom Talpey
Cc: linux-fsdevel, linux-kernel, linux-nfs, Stephen Rothwell
Requesting a delegation on a file from the userland fcntl() interface
currently succeeds when there are conflicting opens present.
This is because the lease handling code ignores conflicting opens for
FL_LAYOUT and FL_DELEG leases. This was a hack put in place long ago,
because nfsd already checks for conflicts in its own way. The kernel
needs to perform this check for userland delegations the same way it is
done for leases, however.
Make this dependent on the lease_manager by adding a new
->lm_open_conflict() lease_manager operation and have
generic_add_lease() call that instead of check_conflicting_open().
Morph check_conflicting_open() into a ->lm_open_conflict() op that is
only called for userland leases/delegations. Set the
->lm_open_conflict() operations for nfsd to trivial functions that
always return 0.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/locks.c | 90 ++++++++++++++++++++++--------------------------
fs/nfsd/nfs4layouts.c | 11 ++++--
fs/nfsd/nfs4state.c | 7 ++++
include/linux/filelock.h | 1 +
4 files changed, 59 insertions(+), 50 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index d4e6af6ac625204b337e94fd1e4f6df2eee5cf50..62fbfce0407b77423e1591290cf57c4e2c5faeb4 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -585,10 +585,50 @@ lease_setup(struct file_lease *fl, void **priv)
__f_setown(filp, task_pid(current), PIDTYPE_TGID, 0);
}
+/**
+ * lease_open_conflict - see if the given file points to an inode that has
+ * an existing open that would conflict with the
+ * desired lease.
+ * @filp: file to check
+ * @arg: type of lease that we're trying to acquire
+ *
+ * Check to see if there's an existing open fd on this file that would
+ * conflict with the lease we're trying to set.
+ */
+static int
+lease_open_conflict(struct file *filp, const int arg)
+{
+ struct inode *inode = file_inode(filp);
+ int self_wcount = 0, self_rcount = 0;
+
+ if (arg == F_RDLCK)
+ return inode_is_open_for_write(inode) ? -EAGAIN : 0;
+ else if (arg != F_WRLCK)
+ return 0;
+
+ /*
+ * Make sure that only read/write count is from lease requestor.
+ * Note that this will result in denying write leases when i_writecount
+ * is negative, which is what we want. (We shouldn't grant write leases
+ * on files open for execution.)
+ */
+ if (filp->f_mode & FMODE_WRITE)
+ self_wcount = 1;
+ else if (filp->f_mode & FMODE_READ)
+ self_rcount = 1;
+
+ if (atomic_read(&inode->i_writecount) != self_wcount ||
+ atomic_read(&inode->i_readcount) != self_rcount)
+ return -EAGAIN;
+
+ return 0;
+}
+
static const struct lease_manager_operations lease_manager_ops = {
.lm_break = lease_break_callback,
.lm_change = lease_modify,
.lm_setup = lease_setup,
+ .lm_open_conflict = lease_open_conflict,
};
/*
@@ -1762,52 +1802,6 @@ int fcntl_getdeleg(struct file *filp, struct delegation *deleg)
return 0;
}
-/**
- * check_conflicting_open - see if the given file points to an inode that has
- * an existing open that would conflict with the
- * desired lease.
- * @filp: file to check
- * @arg: type of lease that we're trying to acquire
- * @flags: current lock flags
- *
- * Check to see if there's an existing open fd on this file that would
- * conflict with the lease we're trying to set.
- */
-static int
-check_conflicting_open(struct file *filp, const int arg, int flags)
-{
- struct inode *inode = file_inode(filp);
- int self_wcount = 0, self_rcount = 0;
-
- if (flags & FL_LAYOUT)
- return 0;
- if (flags & FL_DELEG)
- /* We leave these checks to the caller */
- return 0;
-
- if (arg == F_RDLCK)
- return inode_is_open_for_write(inode) ? -EAGAIN : 0;
- else if (arg != F_WRLCK)
- return 0;
-
- /*
- * Make sure that only read/write count is from lease requestor.
- * Note that this will result in denying write leases when i_writecount
- * is negative, which is what we want. (We shouldn't grant write leases
- * on files open for execution.)
- */
- if (filp->f_mode & FMODE_WRITE)
- self_wcount = 1;
- else if (filp->f_mode & FMODE_READ)
- self_rcount = 1;
-
- if (atomic_read(&inode->i_writecount) != self_wcount ||
- atomic_read(&inode->i_readcount) != self_rcount)
- return -EAGAIN;
-
- return 0;
-}
-
static int
generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **priv)
{
@@ -1844,7 +1838,7 @@ generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **pr
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
- error = check_conflicting_open(filp, arg, lease->c.flc_flags);
+ error = lease->fl_lmops->lm_open_conflict(filp, arg);
if (error)
goto out;
@@ -1901,7 +1895,7 @@ generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **pr
* precedes these checks.
*/
smp_mb();
- error = check_conflicting_open(filp, arg, lease->c.flc_flags);
+ error = lease->fl_lmops->lm_open_conflict(filp, arg);
if (error) {
locks_unlink_lock_ctx(&lease->c);
goto out;
diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
index 683bd1130afe298f9df774684192c89f68102b72..ca7ec7a022bd5c12fad60ff9e51145d9cca55527 100644
--- a/fs/nfsd/nfs4layouts.c
+++ b/fs/nfsd/nfs4layouts.c
@@ -764,9 +764,16 @@ nfsd4_layout_lm_change(struct file_lease *onlist, int arg,
return lease_modify(onlist, arg, dispose);
}
+static int
+nfsd4_layout_lm_open_conflict(struct file *filp, int arg)
+{
+ return 0;
+}
+
static const struct lease_manager_operations nfsd4_layouts_lm_ops = {
- .lm_break = nfsd4_layout_lm_break,
- .lm_change = nfsd4_layout_lm_change,
+ .lm_break = nfsd4_layout_lm_break,
+ .lm_change = nfsd4_layout_lm_change,
+ .lm_open_conflict = nfsd4_layout_lm_open_conflict,
};
int
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 8f8c9385101e15b64883eabec71775f26b14f890..669fabb095407e61525e5b71268cf1f06fc09877 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5543,10 +5543,17 @@ nfsd_change_deleg_cb(struct file_lease *onlist, int arg,
return -EAGAIN;
}
+static int
+nfsd4_deleg_lm_open_conflict(struct file *filp, int arg)
+{
+ return 0;
+}
+
static const struct lease_manager_operations nfsd_lease_mng_ops = {
.lm_breaker_owns_lease = nfsd_breaker_owns_lease,
.lm_break = nfsd_break_deleg_cb,
.lm_change = nfsd_change_deleg_cb,
+ .lm_open_conflict = nfsd4_deleg_lm_open_conflict,
};
static __be32 nfsd4_check_seqid(struct nfsd4_compound_state *cstate, struct nfs4_stateowner *so, u32 seqid)
diff --git a/include/linux/filelock.h b/include/linux/filelock.h
index 54b824c05299261e6bd6acc4175cb277ea35b35d..2f5e5588ee0733c200103801d0d2ba19bebbf9af 100644
--- a/include/linux/filelock.h
+++ b/include/linux/filelock.h
@@ -49,6 +49,7 @@ 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 *);
+ int (*lm_open_conflict)(struct file *, int);
};
struct lock_manager {
--
2.51.1
^ permalink raw reply related [flat|nested] 4+ messages in thread