GFS2: Use only a single address space for rgrps

Prior to this patch, GFS2 had one address space for each rgrp,
stored in the glock. This patch changes them to use a single
address space in the super block. This therefore saves
(sizeof(struct address_space) * nr_of_rgrps) bytes of memory
and for large filesystems, that can be significant.

It would be nice to be able to do something similar and merge
the inode metadata address space into the same global
address space. However, that is rather more complicated as the
on-disk location doesn't have a 1:1 mapping with the inodes in
general. So while it could be done, it will be a more complicated
operation as it requires changing a lot more code paths.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index e6544ee0c137..a99f60c98845 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -736,6 +736,8 @@ struct gfs2_sbd {
 
 	/* Log stuff */
 
+	struct address_space sd_aspace;
+
 	spinlock_t sd_log_lock;
 
 	struct gfs2_trans *sd_log_tr;