linux-kernel - [PATCH 2/2] lib/test_bitmap: test the tail after bitmap_to

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Message-Id: <20220711180930.28271-3-alexandr.lobakin@intel.com>
Date:   Mon, 11 Jul 2022 20:09:30 +0200
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] lib/test_bitmap: test the tail after bitmap_to_arr64()

Currently, test_bitmap_arr64() only tests bitmap_to_arr64()'s sanity
by comparing the result of double-conversion (bm -> arr64 -> bm2)
with the input bitmap. However, this may be not enough when one side
hides bugs of the second one (e.g. tail clearing, which is being
performed by both).
Expand the tests and check the tail of the actual arr64 used as
a temporary buffer for double-converting.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
---
 lib/test_bitmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index d5923a640457..086b1d1db1ca 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -604,6 +604,12 @@ static void __init test_bitmap_arr64(void)
 			pr_err("bitmap_copy_arr64(nbits == %d:"
 				" tail is not safely cleared: %d\n", nbits, next_bit);
 
+		if ((nbits % 64) &&
+		    (arr[(nbits - 1) / 64] & ~GENMASK_ULL((nbits - 1) % 64, 0)))
+			pr_err("bitmap_to_arr64(nbits == %d): tail is not safely cleared: 0x%016llx (must be 0x%016llx)\n",
+			       nbits, arr[(nbits - 1) / 64],
+			       GENMASK_ULL((nbits - 1) % 64, 0));
+
 		if (nbits < EXP1_IN_BITS - 64)
 			expect_eq_uint(arr[DIV_ROUND_UP(nbits, 64)], 0xa5a5a5a5);
 	}
-- 
2.36.1