Unverified Commit 1602bad1 authored by Jeff Layton's avatar Jeff Layton Committed by Christian Brauner
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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: default avatarJeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-17-52f3feebb2f2@kernel.org


Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 8b99f6a8

fs/fcntl.c

+13 −0
Original line number Diff line number Diff line
@@ -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;

	}

fs/locks.c

+40 −5
Original line number Diff line number Diff line
@@ -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);
@@ -1719,6 +1719,7 @@ int fcntl_getlease(struct file *filp) 
		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;

		}
@@ -1730,6 +1731,19 @@ 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, struct delegation *deleg)

{

	if (deleg->d_flags != 0 || deleg->__pad != 0)

		return -EINVAL;

	deleg->d_type = __fcntl_getlease(filp, FL_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
@@ -2039,13 +2053,13 @@ 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 +2095,28 @@ 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);

}



/**

include/linux/filelock.h

+12 −0
Original line number Diff line number Diff line
@@ -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;

include/uapi/linux/fcntl.h

+11 −0
Original line number Diff line number Diff line
@@ -79,6 +79,17 @@ 
 */

#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.

 */