gfs2: eliminate rs_inum and reduce the size of gfs2 inodes

Before this patch, block reservations kept track of the inode
number. At one point, that was a valid thing to do. However, since
we made the reservation a part of the inode (rather than a pointer
to a separate allocated object) the reservation can determine the
inode number by using container_of. This saves us a little memory
in our inode.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/trace_gfs2.h

@@ -606,7 +606,8 @@ TRACE_EVENT(gfs2_rs,
 		__entry->rd_addr	= rs->rs_rbm.rgd->rd_addr;
 		__entry->rd_free_clone	= rs->rs_rbm.rgd->rd_free_clone;
 		__entry->rd_reserved	= rs->rs_rbm.rgd->rd_reserved;
-		__entry->inum		= rs->rs_inum;
+		__entry->inum		= container_of(rs, struct gfs2_inode,
+						       i_res)->i_no_addr;
 		__entry->start		= gfs2_rbm_to_block(&rs->rs_rbm);
 		__entry->free		= rs->rs_free;
 		__entry->func		= func;