xfs: connect up buffer reclaim priority hooks

Now that the buffer reclaim infrastructure can handle different reclaim
priorities for different types of buffers, reconnect the hooks in the
XFS code that has been sitting dormant since it was ported to Linux. This
should finally give use reclaim prioritisation that is on a par with the
functionality that Irix provided XFS 15 years ago.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/xfs_btree.c b/fs/xfs/xfs_btree.c
index 04f9cca..2f9e97c 100644
--- a/fs/xfs/xfs_btree.c
+++ b/fs/xfs/xfs_btree.c
@@ -634,9 +634,8 @@
 		return error;
 	}
 	ASSERT(!bp || !XFS_BUF_GETERROR(bp));
-	if (bp != NULL) {
+	if (bp)
 		XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, refval);
-	}
 	*bpp = bp;
 	return 0;
 }
@@ -944,13 +943,13 @@
 	switch (cur->bc_btnum) {
 	case XFS_BTNUM_BNO:
 	case XFS_BTNUM_CNT:
-		XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_MAP, XFS_ALLOC_BTREE_REF);
+		XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, XFS_ALLOC_BTREE_REF);
 		break;
 	case XFS_BTNUM_INO:
-		XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_INOMAP, XFS_INO_BTREE_REF);
+		XFS_BUF_SET_VTYPE_REF(bp, B_FS_INOMAP, XFS_INO_BTREE_REF);
 		break;
 	case XFS_BTNUM_BMAP:
-		XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_MAP, XFS_BMAP_BTREE_REF);
+		XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, XFS_BMAP_BTREE_REF);
 		break;
 	default:
 		ASSERT(0);