From f9ffed26d6f3e6ac9988947242821579d615fda7 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Tue, 14 Nov 2006 15:51:40 -0500 Subject: 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: J. Bruce Fields --- fs/locks.c | 24 ++++++++++++++++++++++-- include/linux/fs.h | 1 + 2 files changed, 23 insertions(+), 2 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index a65d85c1fdc2..94f5d8065e3a 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -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) @@ -1437,7 +1454,10 @@ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease) int error; lock_kernel(); - error = setlease(filp, arg, lease); + if (filp->f_op && filp->f_op->setlease) + error = filp->f_op->setlease(filp, arg, lease); + else + error = setlease(filp, arg, lease); unlock_kernel(); return error; diff --git a/include/linux/fs.h b/include/linux/fs.h index a24f029accc0..c8ddf34e9710 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -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 { -- cgit v1.2.3