[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/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index 3f3785b..c38fd14 100644
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -397,10 +397,12 @@
 xfs_filestream_init(void)
 {
 	item_zone = kmem_zone_init(sizeof(fstrm_item_t), "fstrm_item");
+	if (!item_zone)
+		return -ENOMEM;
 #ifdef XFS_FILESTREAMS_TRACE
 	xfs_filestreams_trace_buf = ktrace_alloc(XFS_FSTRM_KTRACE_SIZE, KM_SLEEP);
 #endif
-	return item_zone ? 0 : -ENOMEM;
+	return 0;
 }
 
 /*