GFS2: Minor improvements to comments and documentation

This patch simply fixes some comments and the gfs2-glocks.txt file:
Places where i_rwsem was called i_mutex, and adding i_rw_mutex.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>

Documentation/filesystems/gfs2-glocks.txt

@@ -100,14 +100,15 @@ indicates that it is caching uptodate data.
 
 Glock locking order within GFS2:
 
- 1. i_mutex (if required)
+ 1. i_rwsem (if required)
  2. Rename glock (for rename only)
  3. Inode glock(s)
     (Parents before children, inodes at "same level" with same parent in
      lock number order)
  4. Rgrp glock(s) (for (de)allocation operations)
  5. Transaction glock (via gfs2_trans_begin) for non-read operations
- 6. Page lock  (always last, very important!)
+ 6. i_rw_mutex (if required)
+ 7. Page lock  (always last, very important!)
 
 There are two glocks per inode. One deals with access to the inode
 itself (locking order as above), and the other, known as the iopen

fs/gfs2/bmap.c

@@ -1744,7 +1744,7 @@ do_grow_qunlock:
  * @newsize: the size to make the file
  *
  * The file size can grow, shrink, or stay the same size. This
- * is called holding i_mutex and an exclusive glock on the inode
+ * is called holding i_rwsem and an exclusive glock on the inode
  * in question.
  *
  * Returns: errno

fs/gfs2/ops_fstype.c

@@ -825,7 +825,7 @@ static int init_inodes(struct gfs2_sbd *sdp, int undo)
 		goto fail_rindex;
 	}
 	/*
-	 * i_mutex on quota files is special. Since this inode is hidden system
+	 * i_rwsem on quota files is special. Since this inode is hidden system
 	 * file, we are safe to define locking ourselves.
 	 */
 	lockdep_set_class(&sdp->sd_quota_inode->i_rwsem,