bcachefs: improve eytzinger0_find_le self test

Rename eytzinger0_find_test_val() to eytzinger0_find_test_le() and add a
new eytzinger0_find_test_val() wrapper that calls it.

We have already established that the array is sorted in eytzinger order,
so we can use the eytzinger iterator functions and check the boundary
conditions to verify the result of eytzinger0_find_le().

Only scan the entire array if we get an incorrect result.  When we need
to scan, use eytzinger0_for_each_prev() so that we'll stop at the
highest matching element in the array in case there are duplicates;
going through the array linearly wouldn't give us that.

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

1 files changed, 30 insertions, 11 deletions

diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c
index ebe3b5b1e615..d2f7ffcc4fd6 100644
--- a/fs/bcachefs/util.c
+++ b/fs/bcachefs/util.c
@@ -788,29 +788,48 @@ static inline int cmp_u16(const void *_l, const void *_r)
 	return (*l > *r) - (*r > *l);
 }
 
-static void eytzinger0_find_test_val(u16 *test_array, unsigned nr, u16 search)
+static void eytzinger0_find_test_le(u16 *test_array, unsigned nr, u16 search)
 {
-	int i, c1 = -1, c2 = -1;
-	ssize_t r;
+	int r, s;
+	bool bad;
 
 	r = eytzinger0_find_le(test_array, nr,
 			       sizeof(test_array[0]),
 			       cmp_u16, &search);
-	if (r >= 0)
-		c1 = test_array[r];
+	if (r >= 0) {
+		if (test_array[r] > search) {
+			bad = true;
+		} else {
+			s = eytzinger0_next(r, nr);
+			bad = s >= 0 && test_array[s] <= search;
+		}
+	} else {
+		s = eytzinger0_last(nr);
+		bad = s >= 0 && test_array[s] <= search;
+	}
 
-	for (i = 0; i < nr; i++)
-		if (test_array[i] <= search && test_array[i] > c2)
-			c2 = test_array[i];
+	if (bad) {
+		s = -1;
+		eytzinger0_for_each_prev(j, nr) {
+			if (test_array[j] <= search) {
+				s = j;
+				break;
+			}
+		}
 
-	if (c1 != c2) {
 		eytzinger0_for_each(j, nr)
 			pr_info("[%3u] = %12u\n", j, test_array[j]);
-		pr_info("find_le(%2u) -> [%2zi] = %2i should be %2i\n",
-			i, r, c1, c2);
+		pr_info("find_le(%12u) = %3i should be %3i\n",
+			search, r, s);
+		BUG();
 	}
 }
 
+static void eytzinger0_find_test_val(u16 *test_array, unsigned nr, u16 search)
+{
+	eytzinger0_find_test_le(test_array, nr, search);
+}
+
 void eytzinger0_find_test(void)
 {
 	unsigned i, nr, allocated = 1 << 12;