xfs: add a lockdep class key for rtgroup inodes

Add a dynamic lockdep class key for rtgroup inodes.  This will enable
lockdep to deduce inconsistencies in the rtgroup metadata ILOCK locking
order.  Each class can have 8 subclasses, and for now we will only have
2 inodes per group.  This enables rtgroup order and inode order checks
when nesting ILOCKs.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_rtgroup.c

@@ -198,3 +198,55 @@ xfs_rtgroup_trans_join(
 	if (rtglock_flags & XFS_RTGLOCK_BITMAP)
 		xfs_rtbitmap_trans_join(tp);
 }
+
+#ifdef CONFIG_PROVE_LOCKING
+static struct lock_class_key xfs_rtginode_lock_class;
+
+static int
+xfs_rtginode_ilock_cmp_fn(
+	const struct lockdep_map	*m1,
+	const struct lockdep_map	*m2)
+{
+	const struct xfs_inode *ip1 =
+		container_of(m1, struct xfs_inode, i_lock.dep_map);
+	const struct xfs_inode *ip2 =
+		container_of(m2, struct xfs_inode, i_lock.dep_map);
+
+	if (ip1->i_projid < ip2->i_projid)
+		return -1;
+	if (ip1->i_projid > ip2->i_projid)
+		return 1;
+	return 0;
+}
+
+static inline void
+xfs_rtginode_ilock_print_fn(
+	const struct lockdep_map	*m)
+{
+	const struct xfs_inode *ip =
+		container_of(m, struct xfs_inode, i_lock.dep_map);
+
+	printk(KERN_CONT " rgno=%u", ip->i_projid);
+}
+
+/*
+ * Most of the time each of the RTG inode locks are only taken one at a time.
+ * But when committing deferred ops, more than one of a kind can be taken.
+ * However, deferred rt ops will be committed in rgno order so there is no
+ * potential for deadlocks.  The code here is needed to tell lockdep about this
+ * order.
+ */
+static inline void
+xfs_rtginode_lockdep_setup(
+	struct xfs_inode	*ip,
+	xfs_rgnumber_t		rgno,
+	enum xfs_rtg_inodes	type)
+{
+	lockdep_set_class_and_subclass(&ip->i_lock, &xfs_rtginode_lock_class,
+			type);
+	lock_set_cmp_fn(&ip->i_lock, xfs_rtginode_ilock_cmp_fn,
+			xfs_rtginode_ilock_print_fn);
+}
+#else
+#define xfs_rtginode_lockdep_setup(ip, rgno, type)	do { } while (0)
+#endif /* CONFIG_PROVE_LOCKING */