[PATCH 17/17] raid6_kunit: randomize buffer alignment

[Christoph Hellwig <hch@lst.de>]

Add code to add random alignment to the buffers to test the case where
they are not page aligned, and to move the buffers to the end of the
allocation so that they are next to the vmalloc guard page.

This does not include the recovery buffers as the recovery requires
page alignment.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 lib/raid/raid6/tests/raid6_kunit.c | 41 +++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/lib/raid/raid6/tests/raid6_kunit.c b/lib/raid/raid6/tests/raid6_kunit.c
index a0a473643e91..d2fd4a9b74d4 100644
--- a/lib/raid/raid6/tests/raid6_kunit.c
+++ b/lib/raid/raid6/tests/raid6_kunit.c
@@ -20,6 +20,7 @@ MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
 
 static struct rnd_state rng;
 static void *test_buffers[RAID6_KUNIT_MAX_BUFFERS];
+static void *aligned_buffers[RAID6_KUNIT_MAX_BUFFERS];
 static void *test_recov_buffers[RAID6_KUNIT_MAX_FAILURES];
 static size_t test_buflen;
 
@@ -43,6 +44,14 @@ static unsigned int random_length(unsigned int max_length)
 	return (rand32() % (max_length + 1)) & ~511;
 }
 
+/* Generate a random alignment that is a multiple of 64. */
+static unsigned int random_alignment(unsigned int max_alignment)
+{
+	if (max_alignment == 0)
+		return 0;
+	return (rand32() % (max_alignment + 1)) & ~63;
+}
+
 static void makedata(int start, int stop)
 {
 	int i;
@@ -73,7 +82,7 @@ static void test_recover_one(struct kunit *test, unsigned int nr_buffers,
 	for (i = 0; i < RAID6_KUNIT_MAX_FAILURES; i++)
 		memset(test_recov_buffers[i], 0xf0, test_buflen);
 
-	memcpy(dataptrs, test_buffers, sizeof(dataptrs));
+	memcpy(dataptrs, aligned_buffers, sizeof(dataptrs));
 	dataptrs[faila] = test_recov_buffers[0];
 	dataptrs[failb] = test_recov_buffers[1];
 
@@ -95,13 +104,13 @@ static void test_recover_one(struct kunit *test, unsigned int nr_buffers,
 		ta->recov->data2(nr_buffers, len, faila, failb, dataptrs);
 	}
 
-	KUNIT_EXPECT_MEMEQ_MSG(test, test_buffers[faila], test_recov_buffers[0],
+	KUNIT_EXPECT_MEMEQ_MSG(test, aligned_buffers[faila], dataptrs[faila],
 			len,
 			"faila miscompared: %3d[%c] buffers %u len %u (failb=%3d[%c])\n",
 			faila, member_type(nr_buffers, faila),
 			nr_buffers, len,
 			failb, member_type(nr_buffers, failb));
-	KUNIT_EXPECT_MEMEQ_MSG(test, test_buffers[failb], test_recov_buffers[1],
+	KUNIT_EXPECT_MEMEQ_MSG(test, aligned_buffers[failb], dataptrs[failb],
 			len,
 			"failb miscompared: %3d[%c] buffers %u len %u (faila=%3d[%c])\n",
 			failb, member_type(nr_buffers, failb),
@@ -140,9 +149,9 @@ static void test_rmw_one(struct kunit *test, unsigned int nr_buffers,
 {
 	const struct test_args *ta = test->param_value;
 
-	ta->gen->xor_syndrome(nr_buffers, p1, p2, len, test_buffers);
+	ta->gen->xor_syndrome(nr_buffers, p1, p2, len, aligned_buffers);
 	makedata(p1, p2);
-	ta->gen->xor_syndrome(nr_buffers, p1, p2, len, test_buffers);
+	ta->gen->xor_syndrome(nr_buffers, p1, p2, len, aligned_buffers);
 	test_recover(test, nr_buffers, len);
 }
 
@@ -168,13 +177,33 @@ static void raid6_test_one(struct kunit *test)
 	unsigned int nr_buffers =
 		(rand32() % (RAID6_KUNIT_MAX_BUFFERS - 2)) + 3;
 	unsigned int len = random_length(RAID6_KUNIT_MAX_BYTES);
+	unsigned int max_alignment;
+	int i;
 
 	/* Nuke syndromes */
 	memset(test_buffers[nr_buffers - 2], 0xee, test_buflen);
 	memset(test_buffers[nr_buffers - 1], 0xee, test_buflen);
 
+	/*
+	 * If we're not using the entire buffer size, inject randomize alignment
+	 * into the buffer.
+	 */
+	max_alignment = RAID6_KUNIT_MAX_BYTES - len;
+	if (rand32() % 2 == 0) {
+		/* Use random alignments mod 64 */
+		for (i = 0; i < nr_buffers; i++)
+			aligned_buffers[i] = test_buffers[i] +
+				random_alignment(max_alignment);
+	} else {
+		/* Go up to the guard page, to catch buffer overreads */
+		unsigned int align = test_buflen - len;
+
+		for (i = 0; i < nr_buffers; i++)
+			aligned_buffers[i] = test_buffers[i] + align;
+	}
+
 	/* Generate assumed good syndrome */
-	ta->gen->gen_syndrome(nr_buffers, len, test_buffers);
+	ta->gen->gen_syndrome(nr_buffers, len, aligned_buffers);
 
 	test_recover(test, nr_buffers, len);
 
-- 
2.47.3