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authorJ. Bruce Fields <bfields@fieldses.org>2006-11-14 23:51:40 +0300
committerJ. Bruce Fields <bfields@citi.umich.edu>2007-07-19 03:14:47 +0400
commitf9ffed26d6f3e6ac9988947242821579d615fda7 (patch)
treef7dc037b9b1a90511751532be5ebc47c820ed407 /fs/locks.c
parenta9933cea7a1d80dd9efae9f1acd857f5dce742b9 (diff)
downloadlinux-f9ffed26d6f3e6ac9988947242821579d615fda7.tar.xz
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 <bfields@citi.umich.edu>
Diffstat (limited to 'fs/locks.c')
-rw-r--r--fs/locks.c24
1 files changed, 22 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;