ocfs2: temporarily remove extent map caching

The code in extent_map.c is not prepared to deal with a subtree being
rotated between lookups. This can happen when filling holes in sparse files.
Instead of a lengthy patch to update the code (which would likely lose the
benefit of caching subtree roots), we remove most of the algorithms and
implement a simple path based lookup. A less ambitious extent caching scheme
will be added in a later patch.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/inode.h

@@ -43,7 +43,6 @@ struct ocfs2_inode_info
 	spinlock_t			ip_lock;
 	u32				ip_open_count;
 	u32				ip_clusters;
-	struct ocfs2_extent_map		ip_map;
 	struct list_head		ip_io_markers;
 
 	struct mutex			ip_io_mutex;