[XFS] streamline init/exit path

Currently the xfs module init/exit code is a mess. It's farmed out over a
lot of function with very little error checking. This patch makes sure we
propagate all initialization failures properly and clean up after them.
Various runtime initializations are replaced with compile-time
initializations where possible to make this easier. The exit path is
similarly consolidated.

There's now split out function to create/destroy the kmem zones and
alloc/free the trace buffers. I've also changed the ktrace allocations to
KM_MAYFAIL and handled errors resulting from that.

And yes, we really should replace the XFS_*_TRACE ifdefs with a single
XFS_TRACE..

SGI-PV: 976035

SGI-Modid: xfs-linux-melb:xfs-kern:31354a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Niv Sardi <xaiki@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
diff --git a/fs/xfs/linux-2.6/xfs_sysctl.c b/fs/xfs/linux-2.6/xfs_sysctl.c
index bb997d7..7dacb5b 100644
--- a/fs/xfs/linux-2.6/xfs_sysctl.c
+++ b/fs/xfs/linux-2.6/xfs_sysctl.c
@@ -259,15 +259,17 @@
 	{}
 };
 
-void
+int
 xfs_sysctl_register(void)
 {
 	xfs_table_header = register_sysctl_table(xfs_root_table);
+	if (!xfs_table_header)
+		return -ENOMEM;
+	return 0;
 }
 
 void
 xfs_sysctl_unregister(void)
 {
-	if (xfs_table_header)
-		unregister_sysctl_table(xfs_table_header);
+	unregister_sysctl_table(xfs_table_header);
 }