bcachefs: implement eytzinger0_find_ge directly

Implement eytzinger0_find_ge() directly instead of implementing it in
terms of eytzinger0_find_le() and adjusting the result.

This turns eytzinger0_find_ge() into a minimum search, so when there are
duplicate elements, the result of eytzinger0_find_ge() will now always
point at the first matching element.

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

diff --git a/fs/bcachefs/eytzinger.h b/fs/bcachefs/eytzinger.h
index 568a04b16d0938eb5ee6c7a0ebf4fa99e0efe200..e3713b7b4c27614216a2b6ce0b4f1dea3ca29fd0 100644 (file)
--- a/fs/bcachefs/eytzinger.h
+++ b/fs/bcachefs/eytzinger.h
@@ -275,15 +275,17 @@ static inline int eytzinger0_find_gt(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_ge(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);
-
-       if (idx < nr && !cmp(base + idx * size, search))
-               return idx;
+       void *base1 = base - size;
+       unsigned n = 1;
 
-       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;
 }
 
 #define eytzinger0_find(base, nr, size, _cmp, search)                  \