locks: comment cleanups and clarifications

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 31 insertions, 8 deletions

diff --git a/fs/locks.c b/fs/locks.c
index 804bb9e01a65..ddeab49fe2be 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -518,9 +518,10 @@ static void locks_insert_block(struct file_lock *blocker,
                 list_add(&waiter->fl_link, &blocked_list);
 }
 
-/* Wake up processes blocked waiting for blocker.
- * If told to wait then schedule the processes until the block list
- * is empty, otherwise empty the block list ourselves.
+/*
+ * Wake up processes blocked waiting for blocker.
+ *
+ * Must be called with the file_lock_lock held!
  */
 static void locks_wake_up_blocks(struct file_lock *blocker)
 {
@@ -806,6 +807,11 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
         }
 
         lock_flocks();
+        /*
+         * New lock request. Walk all POSIX locks and look for conflicts. If
+         * there are any, either return error or put the request on the
+         * blocker's list of waiters and the global blocked_list.
+         */
         if (request->fl_type != F_UNLCK) {
                 for_each_lock(inode, before) {
                         fl = *before;
@@ -844,7 +850,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
                 before = &fl->fl_next;
         }
 
-        /* Process locks with this owner.  */
+        /* Process locks with this owner. */
         while ((fl = *before) && posix_same_owner(request, fl)) {
                 /* Detect adjacent or overlapping regions (if same lock type)
                  */
@@ -930,10 +936,9 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
         }
 
         /*
-         * The above code only modifies existing locks in case of
-         * merging or replacing.  If new lock(s) need to be inserted
-         * all modifications are done bellow this, so it's safe yet to
-         * bail out.
+         * The above code only modifies existing locks in case of merging or
+         * replacing. If new lock(s) need to be inserted all modifications are
+         * done below this, so it's safe yet to bail out.
          */
         error = -ENOLCK; /* "no luck" */
         if (right && left == right && !new_fl2)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6cfc9a29a783..ed9fdaaf3223 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -926,6 +926,24 @@ int locks_in_grace(struct net *);
 /* 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 */