locks: comment cleanups and clarifications
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6cfc9a2..ed9fdaa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -926,6 +926,24 @@
/* that will die - we need it for nfs_lock_info */
#include <linux/nfs_fs_i.h>
+/*
+ * struct file_lock represents a generic "file lock". It's used to represent
+ * POSIX byte range locks, BSD (flock) locks, and leases. It's important to
+ * note that the same struct is used to represent both a request for a lock and
+ * the lock itself, but the same object is never used for both.
+ *
+ * FIXME: should we create a separate "struct lock_request" to help distinguish
+ * these two uses?
+ *
+ * The i_flock list is ordered by:
+ *
+ * 1) lock type -- FL_LEASEs first, then FL_FLOCK, and finally FL_POSIX
+ * 2) lock owner
+ * 3) lock range start
+ * 4) lock range end
+ *
+ * Obviously, the last two criteria only matter for POSIX locks.
+ */
struct file_lock {
struct file_lock *fl_next; /* singly linked list for this inode */
struct list_head fl_link; /* doubly linked list of all locks */