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Commit f9ffed26 authored by J. Bruce Fields's avatar J. Bruce Fields Committed by J. Bruce Fields
Browse files

locks: provide a file lease method enabling cluster-coherent leases 



Currently leases are only kept locally, so there's no way for a distributed
filesystem to enforce them against multiple clients.  We're particularly
interested in the case of nfsd exporting a cluster filesystem, in which
case nfsd needs cluster-coherent leases in order to implement delegations
correctly.

Also add some documentation.

Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
parent a9933cea

fs/locks.c

+22 −2
Original line number Diff line number Diff line
@@ -1429,7 +1429,24 @@ out: 
 *	@lease: file_lock to use

 *

 *	Call this to establish a lease on the file.

 *	The fl_lmops fl_break function is required by break_lease

 *	The (*lease)->fl_lmops->fl_break operation must be set; if not,

 *	break_lease will oops!

 *

 *	This will call the filesystem's setlease file method, if

 *	defined.  Note that there is no getlease method; instead, the

 *	filesystem setlease method should call back to setlease() to

 *	add a lease to the inode's lease list, where fcntl_getlease() can

 *	find it.  Since fcntl_getlease() only reports whether the current

 *	task holds a lease, a cluster filesystem need only do this for

 *	leases held by processes on this node.

 *

 *	There is also no break_lease method; filesystems that

 *	handle their own leases shoud break leases themselves from the

 *	filesystem's open, create, and (on truncate) setattr methods.

 *

 *	Warning: the only current setlease methods exist only to disable

 *	leases in certain cases.  More vfs changes may be required to

 *	allow a full filesystem lease implementation.

 */



int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
@@ -1437,6 +1454,9 @@ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease) 
	int error;



	lock_kernel();

	if (filp->f_op && filp->f_op->setlease)

		error = filp->f_op->setlease(filp, arg, lease);

	else

		error = setlease(filp, arg, lease);

	unlock_kernel();

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -1122,6 +1122,7 @@ struct file_operations { 
	int (*flock) (struct file *, int, struct file_lock *);

	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);

	ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);

	int (*setlease)(struct file *, long, struct file_lock **);

};



struct inode_operations {