bcachefs: add eytzinger0_for_each_prev

Add an eytzinger0_for_each_prev() macro for iterating through an
eytzinger array in reverse.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c
index 4114e5264965..ebe3b5b1e615 100644
--- a/fs/bcachefs/util.c
+++ b/fs/bcachefs/util.c
@@ -769,6 +769,15 @@ void eytzinger0_test(void)
 			inorder++;
 		}
 		BUG_ON(inorder != size);
+
+		inorder = size - 1;
+		eytzinger0_for_each_prev(eytz, size) {
+			BUG_ON(eytz != eytzinger0_first(size) &&
+			       eytzinger0_next(eytzinger0_prev(eytz, size), size) != eytz);
+
+			inorder--;
+		}
+		BUG_ON(inorder != -1);
 	}
 }