xfs: pass xfsstats structures to handlers and macros

This patch is the next step toward per-fs xfs stats. The patch makes
the show and clear routines able to handle any stats structure
associated with a kobject.

Instead of a single global xfsstats structure, add kobject and a pointer
to a per-cpu struct xfsstats. Modify the macros that manipulate the stats
accordingly: XFS_STATS_INC, XFS_STATS_DEC, and XFS_STATS_ADD now access
xfsstats->xs_stats.

The sysfs functions need to get from the kobject back to the xfsstats
structure which contains it, and pass the pointer to the ->xs_stats
percpu structure into the show & clear routines.

Signed-off-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_sysctl.c

@@ -37,7 +37,7 @@ xfs_stats_clear_proc_handler(
 	ret = proc_dointvec_minmax(ctl, write, buffer, lenp, ppos);
 
 	if (!ret && write && *valp) {
-		xfs_stats_clearall();
+		xfs_stats_clearall(xfsstats.xs_stats);
 		xfs_stats_clear = 0;
 	}