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/incore.h

@@ -295,7 +295,6 @@ struct gfs2_blkreserv {
 	struct rb_node rs_node;       /* link to other block reservations */
 	struct gfs2_rbm rs_rbm;       /* Start of reservation */
 	u32 rs_free;                  /* how many blocks are still free */
-	u64 rs_inum;                  /* Inode number for reservation */
 };
 
 /*

fs/gfs2/rgrp.c

@@ -607,8 +607,10 @@ int gfs2_rsqa_alloc(struct gfs2_inode *ip)
 
 static void dump_rs(struct seq_file *seq, const struct gfs2_blkreserv *rs)
 {
+	struct gfs2_inode *ip = container_of(rs, struct gfs2_inode, i_res);
+
 	gfs2_print_dbg(seq, "  B: n:%llu s:%llu b:%u f:%u\n",
-		       (unsigned long long)rs->rs_inum,
+		       (unsigned long long)ip->i_no_addr,
 		       (unsigned long long)gfs2_rbm_to_block(&rs->rs_rbm),
 		       rs->rs_rbm.offset, rs->rs_free);
 }
@@ -1528,7 +1530,6 @@ static void rg_mblk_search(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip,
 	if (ret == 0) {
 		rs->rs_rbm = rbm;
 		rs->rs_free = extlen;
-		rs->rs_inum = ip->i_no_addr;
 		rs_insert(ip);
 	} else {
 		if (goal == rgd->rd_last_alloc + rgd->rd_data0)

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;