fbarray lookahead/lookbehind fixes

index 26a51e2a3e..bf89b99e5b 100644
@@ -103,6 +103,14 @@ static int empty_msk_test_setup(void)
 	return 0;
 }
 
+static int lookahead_test_setup(void)
+{
+	/* set index 64 as used */
+	param.start = 64;
+	param.end = 64;
+	return init_array();
+}
+
 static int test_invalid(void)
 {
 	struct rte_fbarray dummy;

@@ -709,6 +717,20 @@ static int test_empty(void)
 	return TEST_SUCCESS;
 }
 
+static int test_lookahead(void)
+{
+	int ret;
+
+	/* run regular test first */
+	ret = test_find();
+	if (ret != TEST_SUCCESS)
+		return ret;
+
+	/* test if we can find free chunk while not starting with 0 */
+	TEST_ASSERT_EQUAL(rte_fbarray_find_next_n_free(&param.arr, 1, param.start),
+			param.start + 1, "Free chunk index is wrong\n");
+	return TEST_SUCCESS;
+}
 
 static struct unit_test_suite fbarray_test_suite = {
 	.suite_name = "fbarray autotest",

@@ -723,6 +745,7 @@ static struct unit_test_suite fbarray_test_suite = {
 		TEST_CASE_ST(last_msk_test_setup, reset_array, test_find),
 		TEST_CASE_ST(full_msk_test_setup, reset_array, test_find),
 		TEST_CASE_ST(empty_msk_test_setup, reset_array, test_empty),
+		TEST_CASE_ST(lookahead_test_setup, reset_array, test_lookahead),
 		TEST_CASES_END()
 	}
 };

index 0fe5bcfe06..2680b34823 100644
@@ -236,7 +236,8 @@ find_next_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
 				 * as well, so skip that on next iteration.
 				 */
 				ignore_msk = ~((1ULL << need) - 1);
-				msk_idx = lookahead_idx;
+				/* outer loop will increment msk_idx so add 1 */
+				msk_idx = lookahead_idx - 1;
 				break;
 			}
 

index bf89b99e5b..147d6e2a07 100644
@@ -111,6 +111,14 @@ static int lookahead_test_setup(void)
 	return init_array();
 }
 
+static int lookbehind_test_setup(void)
+{
+	/* set index 63 as used */
+	param.start = 63;
+	param.end = 63;
+	return init_array();
+}
+
 static int test_invalid(void)
 {
 	struct rte_fbarray dummy;

@@ -732,6 +740,21 @@ static int test_lookahead(void)
 	return TEST_SUCCESS;
 }
 
+static int test_lookbehind(void)
+{
+	int ret, free_len = 2;
+
+	/* run regular test first */
+	ret = test_find();
+	if (ret != TEST_SUCCESS)
+		return ret;
+
+	/* test if we can find free chunk while crossing mask boundary */
+	TEST_ASSERT_EQUAL(rte_fbarray_find_prev_n_free(&param.arr, param.start + 1, free_len),
+			param.start - free_len, "Free chunk index is wrong\n");
+	return TEST_SUCCESS;
+}
+
 static struct unit_test_suite fbarray_test_suite = {
 	.suite_name = "fbarray autotest",
 	.setup = autotest_setup,

@@ -746,6 +769,7 @@ static struct unit_test_suite fbarray_test_suite = {
 		TEST_CASE_ST(full_msk_test_setup, reset_array, test_find),
 		TEST_CASE_ST(empty_msk_test_setup, reset_array, test_empty),
 		TEST_CASE_ST(lookahead_test_setup, reset_array, test_lookahead),
+		TEST_CASE_ST(lookbehind_test_setup, reset_array, test_lookbehind),
 		TEST_CASES_END()
 	}
 };

index 2680b34823..b4f0b0b0c3 100644
@@ -512,7 +512,8 @@ find_prev_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
 				 * as well, so skip that on next iteration.
 				 */
 				ignore_msk = UINT64_MAX << need;
-				msk_idx = lookbehind_idx;
+				/* outer loop will decrement msk_idx so add 1 */
+				msk_idx = lookbehind_idx + 1;
 				break;
 			}
 

index 147d6e2a07..4b17ef6be3 100644
@@ -755,6 +755,32 @@ static int test_lookbehind(void)
 	return TEST_SUCCESS;
 }
 
+static int test_lookahead_mask(void)
+{
+	/*
+	 * There is a certain type of lookahead behavior we want to test here,
+	 * namely masking of bits that were scanned with lookahead but that we
+	 * know do not match our criteria. This is achieved in following steps:
+	 *
+	 *   0. Look for a big enough chunk of free space (say, 62 elements)
+	 *   1. Trigger lookahead by breaking a run somewhere inside mask 0
+	 *      (indices 0-63)
+	 *   2. Fail lookahead by breaking the run somewhere inside mask 1
+	 *      (indices 64-127)
+	 *   3. Ensure that we can still find free space in mask 1 afterwards
+	 */
+
+	/* break run on first mask */
+	rte_fbarray_set_used(&param.arr, 61);
+	/* break run on second mask */
+	rte_fbarray_set_used(&param.arr, 70);
+
+	/* we expect to find free space at 71 */
+	TEST_ASSERT_EQUAL(rte_fbarray_find_next_n_free(&param.arr, 0, 62),
+			71, "Free chunk index is wrong\n");
+	return TEST_SUCCESS;
+}
+
 static struct unit_test_suite fbarray_test_suite = {
 	.suite_name = "fbarray autotest",
 	.setup = autotest_setup,

@@ -770,6 +796,8 @@ static struct unit_test_suite fbarray_test_suite = {
 		TEST_CASE_ST(empty_msk_test_setup, reset_array, test_empty),
 		TEST_CASE_ST(lookahead_test_setup, reset_array, test_lookahead),
 		TEST_CASE_ST(lookbehind_test_setup, reset_array, test_lookbehind),
+		/* setup for these tests is more complex so do it in test func */
+		TEST_CASE_ST(NULL, reset_array, test_lookahead_mask),
 		TEST_CASES_END()
 	}
 };

index b4f0b0b0c3..195f8394be 100644
@@ -216,6 +216,8 @@ find_next_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
 		for (lookahead_idx = msk_idx + 1; lookahead_idx < msk->n_masks;
 				lookahead_idx++) {
 			unsigned int s_idx, need;
+			uint64_t first_bit = 1;
+
 			lookahead_msk = msk->data[lookahead_idx];
 
 			/* if we're looking for free space, invert the mask */

@@ -225,17 +227,22 @@ find_next_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
 			/* figure out how many consecutive bits we need here */
 			need = RTE_MIN(left, MASK_ALIGN);
 
-			for (s_idx = 0; s_idx < need - 1; s_idx++)
+			/* count number of shifts we performed */
+			for (s_idx = 0; s_idx < need - 1; s_idx++) {
 				lookahead_msk &= lookahead_msk >> 1ULL;
+				/* did we lose the run yet? */
+				if ((lookahead_msk & first_bit) == 0)
+					break;
+			}
 
 			/* if first bit is not set, we've lost the run */
-			if ((lookahead_msk & 1) == 0) {
+			if ((lookahead_msk & first_bit) == 0) {
 				/*
 				 * we've scanned this far, so we know there are
 				 * no runs in the space we've lookahead-scanned
 				 * as well, so skip that on next iteration.
 				 */
-				ignore_msk = ~((1ULL << need) - 1);
+				ignore_msk = ~((1ULL << (s_idx + 1)) - 1);
 				/* outer loop will increment msk_idx so add 1 */
 				msk_idx = lookahead_idx - 1;
 				break;

index 4b17ef6be3..13c6691e50 100644
@@ -781,6 +781,32 @@ static int test_lookahead_mask(void)
 	return TEST_SUCCESS;
 }
 
+static int test_lookbehind_mask(void)
+{
+	/*
+	 * There is a certain type of lookbehind behavior we want to test here,
+	 * namely masking of bits that were scanned with lookbehind but that we
+	 * know do not match our criteria. This is achieved in two steps:
+	 *
+	 *   0. Look for a big enough chunk of free space (say, 62 elements)
+	 *   1. Trigger lookbehind by breaking a run somewhere inside mask 2
+	 *      (indices 128-191)
+	 *   2. Fail lookbehind by breaking the run somewhere inside mask 1
+	 *      (indices 64-127)
+	 *   3. Ensure that we can still find free space in mask 1 afterwards
+	 */
+
+	/* break run on mask 2 */
+	rte_fbarray_set_used(&param.arr, 130);
+	/* break run on mask 1 */
+	rte_fbarray_set_used(&param.arr, 70);
+
+	/* start from 190, we expect to find free space at 8 */
+	TEST_ASSERT_EQUAL(rte_fbarray_find_prev_n_free(&param.arr, 190, 62),
+			8, "Free chunk index is wrong\n");
+	return TEST_SUCCESS;
+}
+
 static struct unit_test_suite fbarray_test_suite = {
 	.suite_name = "fbarray autotest",
 	.setup = autotest_setup,

@@ -798,6 +824,7 @@ static struct unit_test_suite fbarray_test_suite = {
 		TEST_CASE_ST(lookbehind_test_setup, reset_array, test_lookbehind),
 		/* setup for these tests is more complex so do it in test func */
 		TEST_CASE_ST(NULL, reset_array, test_lookahead_mask),
+		TEST_CASE_ST(NULL, reset_array, test_lookbehind_mask),
 		TEST_CASES_END()
 	}
 };

index 195f8394be..63d8b731f5 100644
@@ -508,8 +508,13 @@ find_prev_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
 			/* figure out how many consecutive bits we need here */
 			need = RTE_MIN(left, MASK_ALIGN);
 
-			for (s_idx = 0; s_idx < need - 1; s_idx++)
+			/* count number of shifts we performed */
+			for (s_idx = 0; s_idx < need - 1; s_idx++) {
 				lookbehind_msk &= lookbehind_msk << 1ULL;
+				/* did we lose the run yet? */
+				if ((lookbehind_msk & last_bit) == 0)
+					break;
+			}
 
 			/* if last bit is not set, we've lost the run */
 			if ((lookbehind_msk & last_bit) == 0) {

@@ -518,7 +523,7 @@ find_prev_n(const struct rte_fbarray *arr, unsigned int start, unsigned int n,
 				 * no runs in the space we've lookbehind-scanned
 				 * as well, so skip that on next iteration.
 				 */
-				ignore_msk = UINT64_MAX << need;
+				ignore_msk = ~(UINT64_MAX << (MASK_ALIGN - s_idx - 1));
 				/* outer loop will decrement msk_idx so add 1 */
 				msk_idx = lookbehind_idx + 1;
 				break;