linux-kernel - [PATCH 1/2 v2] f2fs: fix wrong calculation of block age

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: <20230116030850.20260-1-qixiaoyu1@xiaomi.com>
Date:   Mon, 16 Jan 2023 11:08:49 +0800
From:   qixiaoyu1 <qxy65535@...il.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, qixiaoyu1@...omi.com,
        xiongping1@...omi.com
Subject: [PATCH 1/2 v2] f2fs: fix wrong calculation of block age

Currently we wrongly calculate the new block age to
old * LAST_AGE_WEIGHT / 100.

Fix it to new * (100 - LAST_AGE_WEIGHT) / 100
                + old * LAST_AGE_WEIGHT / 100.

Signed-off-by: qixiaoyu1 <qixiaoyu1@...omi.com>
Signed-off-by: xiongping1 <xiongping1@...omi.com>
---
Change log v1 -> v2:
 - fix udiv

 fs/f2fs/extent_cache.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 342af24b2f8c..ad5533f178fd 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -874,11 +874,8 @@ void f2fs_update_read_extent_tree_range_compressed(struct inode *inode,
 static unsigned long long __calculate_block_age(unsigned long long new,
 						unsigned long long old)
 {
-	unsigned long long diff;
-
-	diff = (new >= old) ? new - (new - old) : new + (old - new);
-
-	return div_u64(diff * LAST_AGE_WEIGHT, 100);
+	return div_u64(new, 100) * (100 - LAST_AGE_WEIGHT)
+		+ div_u64(old, 100) * LAST_AGE_WEIGHT;
 }
 
 /* This returns a new age and allocated blocks in ei */
-- 
2.36.1