[Cluster-devel] GFS2: The war on bloat

[Steven Whitehouse]

The following patch shrinks the gfs2_args structure which is embedded in
every GFS2 superblock. It cuts down the size of the options to a single
unsigned int (the 13 bits of bitfields will be rounded up to that size
by the compiler) from the current 11 unsigned ints. So on x86 thats 44
bytes shrinking to 4 bytes, in each and every GFS2 superblock.

Signed-off-by: Steven Whitehouse <swhitho at redhat.com>

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index a1777a1..b2c5784 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -386,21 +386,21 @@ struct gfs2_statfs_change_host {
 #define GFS2_DATA_ORDERED	2
 
 struct gfs2_args {
-	char ar_lockproto[GFS2_LOCKNAME_LEN]; /* Name of the Lock Protocol */
-	char ar_locktable[GFS2_LOCKNAME_LEN]; /* Name of the Lock Table */
-	char ar_hostdata[GFS2_LOCKNAME_LEN]; /* Host specific data */
-	int ar_spectator; /* Don't get a journal because we're always RO */
-	int ar_ignore_local_fs; /* Don't optimize even if local_fs is 1 */
-	int ar_localflocks; /* Let the VFS do flock|fcntl locks for us */
-	int ar_localcaching; /* Local-style caching (dangerous on multihost) */
-	int ar_debug; /* Oops on errors instead of trying to be graceful */
-	int ar_upgrade; /* Upgrade ondisk/multihost format */
-	unsigned int ar_num_glockd; /* Number of glockd threads */
-	int ar_posix_acl; /* Enable posix acls */
-	int ar_quota; /* off/account/on */
-	int ar_suiddir; /* suiddir support */
-	int ar_data; /* ordered/writeback */
-	int ar_meta; /* mount metafs */
+	char ar_lockproto[GFS2_LOCKNAME_LEN];	/* Name of the Lock Protocol */
+	char ar_locktable[GFS2_LOCKNAME_LEN];	/* Name of the Lock Table */
+	char ar_hostdata[GFS2_LOCKNAME_LEN];	/* Host specific data */
+	unsigned int ar_spectator:1;		/* Don't get a journal */
+	unsigned int ar_ignore_local_fs:1;	/* Ignore optimisations */
+	unsigned int ar_localflocks:1;		/* Let the VFS do flock|fcntl */
+	unsigned int ar_localcaching:1;		/* Local caching */
+	unsigned int ar_debug:1;		/* Oops on errors */
+	unsigned int ar_upgrade:1;		/* Upgrade ondisk format */
+	unsigned int ar_posix_acl:1;		/* Enable posix acls */
+	unsigned int ar_quota:2;		/* off/account/on */
+	unsigned int ar_suiddir:1;		/* suiddir support */
+	unsigned int ar_data:2;			/* ordered/writeback */
+	unsigned int ar_meta:1;			/* mount metafs */
+	unsigned int ar_num_glockd;		/* Number of glockd threads */
 };
 
 struct gfs2_tune {