[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_stats.c b/fs/xfs/linux-2.6/xfs_stats.c
index e480b61..3d5b67c 100644
--- a/fs/xfs/linux-2.6/xfs_stats.c
+++ b/fs/xfs/linux-2.6/xfs_stats.c
@@ -98,12 +98,21 @@
 	return len;
 }
 
-void
+int
 xfs_init_procfs(void)
 {
 	if (!proc_mkdir("fs/xfs", NULL))
-		return;
-	create_proc_read_entry("fs/xfs/stat", 0, NULL, xfs_read_xfsstats, NULL);
+		goto out;
+
+	if (!create_proc_read_entry("fs/xfs/stat", 0, NULL,
+			xfs_read_xfsstats, NULL))
+		goto out_remove_entry;
+	return 0;
+
+ out_remove_entry:
+	remove_proc_entry("fs/xfs", NULL);
+ out:
+	return -ENOMEM;
 }
 
 void