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From:   qixiaoyu1 <qxy65535@gmail.com>
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <chao@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, xiongping1@xiaomi.com,
        qixiaoyu1 <qixiaoyu1@xiaomi.com>
Subject: [PATCH 1/2] f2fs: fix wrong calculation of block age
Date:   Fri, 13 Jan 2023 20:58:58 +0800
Message-Id: <20230113125859.15651-1-qixiaoyu1@xiaomi.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@xiaomi.com>
---
 fs/f2fs/extent_cache.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 342af24b2f8c..93a1ab186517 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -874,11 +874,7 @@ 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 new - new / 100 * LAST_AGE_WEIGHT + old / 100 * LAST_AGE_WEIGHT;
 }
 
 /* This returns a new age and allocated blocks in ei */
-- 
2.36.1