[Cluster-devel] [GFS2 PATCH] Reduce size of version numbers

[Bob Peterson <rpeterso@redhat.com>]

Hi,

This patch changes the version number values in three
structures from 64-bit to 16-bit.  These values are
never compared in a greater-than or less-than, so
wrap-around shouldn't be an issue.  Eventually we can
get rid of these altogether in favor of a bit or two.
The locations were moved to facilitate intelligent data
packing by the compiler.

Regards,

Bob Peterson
Red Hat GFS

Signed-off-by: Bob Peterson <rpeterso@redhat.com> 
--
 fs/gfs2/incore.h |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 9c090e1..ab682c0 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -85,7 +85,6 @@ struct gfs2_rgrpd {
 	u32 rd_data;			/* num of data blocks in rgrp */
 	u32 rd_bitbytes;		/* number of bytes in data bitmaps */
 	struct gfs2_rgrp_host rd_rg;
-	u64 rd_rg_vn;
 	struct gfs2_bitmap *rd_bits;
 	unsigned int rd_bh_count;
 	struct mutex rd_mutex;
@@ -94,6 +93,7 @@ struct gfs2_rgrpd {
 	u32 rd_last_alloc_data;
 	u32 rd_last_alloc_meta;
 	struct gfs2_sbd *rd_sbd;
+	u16 rd_rg_vn;
 	unsigned char rd_flags;
 #define GFS2_RDF_CHECK        0x01      /* Need to check for unlinked inodes */
 #define GFS2_RDF_NOALLOC      0x02      /* rg prohibits allocation */
@@ -197,7 +197,6 @@ struct gfs2_glock {
 	char *gl_lvb;
 	atomic_t gl_lvb_count;
 
-	u64 gl_vn;
 	unsigned long gl_stamp;
 	unsigned long gl_tchange;
 	void *gl_object;
@@ -210,6 +209,7 @@ struct gfs2_glock {
 	struct list_head gl_ail_list;
 	atomic_t gl_ail_count;
 	struct delayed_work gl_work;
+	u16 gl_vn;
 };
 
 struct gfs2_alloc {
@@ -532,7 +532,7 @@ struct gfs2_sbd {
 
 	/* Resource group stuff */
 
-	u64 sd_rindex_vn;
+	u16 sd_rindex_vn;
 	spinlock_t sd_rindex_spin;
 	struct mutex sd_rindex_mutex;
 	struct list_head sd_rindex_list;