ext4: Make ext4_ext_find_extent fills ext_path completely

When pos=0 or depth, the fields of ext4_ext_path is are not
completely filled.  This patch also removes some unnecessary code.
Signed-off-by: NShen Feng <shen@cn.fujitsu.com>
Signed-off-by: NMingming Cao <cmm@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/extents.c

@@ -524,6 +524,7 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
 		alloc = 1;
 	}
 	path[0].p_hdr = eh;
+	path[0].p_bh = NULL;
 
 	i = depth;
 	/* walk through the tree */
@@ -552,12 +553,14 @@ ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
 	}
 
 	path[ppos].p_depth = i;
-	path[ppos].p_hdr = eh;
 	path[ppos].p_ext = NULL;
 	path[ppos].p_idx = NULL;
 
 	/* find extent */
 	ext4_ext_binsearch(inode, path + ppos, block);
+	/* if not an empty leaf */
+	if (path[ppos].p_ext)
+		path[ppos].p_block = ext_pblock(path[ppos].p_ext);
 
 	ext4_ext_show_path(inode, path);