[XFS] Fix up sparse warnings.

These are mostly locking annotations, marking things static, casts where
needed and declaring stuff in header files.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:30002a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
diff --git a/fs/xfs/xfs_bmap.h b/fs/xfs/xfs_bmap.h
index 68267d7..87224b7 100644
--- a/fs/xfs/xfs_bmap.h
+++ b/fs/xfs/xfs_bmap.h
@@ -25,6 +25,8 @@
 struct xfs_mount;
 struct xfs_trans;
 
+extern kmem_zone_t	*xfs_bmap_free_item_zone;
+
 /*
  * DELTA: describe a change to the in-core extent list.
  *