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/dlmglue.c

@@ -1614,10 +1614,6 @@ static int ocfs2_meta_lock_update(struct inode *inode,
 	 * for the inode metadata. */
 	ocfs2_metadata_cache_purge(inode);
 
-	/* will do nothing for inode types that don't use the extent
-	 * map (bitmap files, etc) */
-	ocfs2_extent_map_trunc(inode, 0);
-
 	if (ocfs2_meta_lvb_is_trustable(inode, lockres)) {
 		mlog(0, "Trusting LVB on inode %llu\n",
 		     (unsigned long long)oi->ip_blkno);