bcachefs: implement eytzinger0_find_gt directly

Instead of implementing eytzinger0_find_gt() in terms of
eytzinger0_find_le() and adjusting the result, implement it directly.

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

1 files changed, 7 insertions, 10 deletions

diff --git a/fs/bcachefs/eytzinger.h b/fs/bcachefs/eytzinger.h
index a530dbcde476..568a04b16d09 100644
--- a/fs/bcachefs/eytzinger.h
+++ b/fs/bcachefs/eytzinger.h
@@ -262,20 +262,17 @@ static inline int eytzinger0_find_le(void *base, size_t nr, size_t size,
 	return n - 1;
 }
 
+/* return smallest node > @search, or -1 if not found */
 static inline int eytzinger0_find_gt(void *base, size_t nr, size_t size,
 				     cmp_func_t cmp, const void *search)
 {
-	ssize_t idx = eytzinger0_find_le(base, nr, size, cmp, search);
+	void *base1 = base - size;
+	unsigned n = 1;
 
-	/*
-	 * if eytitzinger0_find_le() returned -1 - no element was <= search - we
-	 * want to return the first element; next/prev identities mean this work
-	 * as expected
-	 *
-	 * similarly if find_le() returns last element, we should return -1;
-	 * identities mean this all works out:
-	 */
-	return eytzinger0_next(idx, nr);
+	while (n <= nr)
+		n = eytzinger1_child(n, cmp(base1 + n * size, search) <= 0);
+	n >>= __ffs(n + 1) + 1;
+	return n - 1;
 }
 
 static inline int eytzinger0_find_ge(void *base, size_t nr, size_t size,