linux-kernel - [PATCH 09/12] bitmap: optimize bitmap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230828184353.5145-10-yury.norov@gmail.com>
Date:   Mon, 28 Aug 2023 11:43:49 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH 09/12] bitmap: optimize bitmap_remap() when 'new' is empty map

When 'new' map is empty, we can skip remapping entirely and replace it
with bitmap_copy().

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 lib/bitmap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 2e8deeb8bf99..50385d61e6ea 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -1003,6 +1003,11 @@ void __bitmap_remap(unsigned long *dst, const unsigned long *src,
 	bitmap_zero(dst, nbits);
 
 	w = bitmap_weight(new, nbits);
+	if (w == 0) {
+		bitmap_copy(dst, src, nbits);
+		return;
+	}
+
 	for_each_set_bit(oldbit, src, nbits) {
 		int n = bitmap_pos_to_ord(old, oldbit, nbits);
 
-- 
2.39.2