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@xiaomi.com>
Signed-off-by: xiongping1 <xiongping1@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 1daf8c88c09bfde7faf807d056d96c85b4de4d5d..c8efc957c230bbc1a2a72fea5bb585fd2bf5033f 100644 (file)
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -874,11 +874,18 @@ unlock_out:
 static unsigned long long __calculate_block_age(unsigned long long new,
                                                unsigned long long old)
 {
-       unsigned long long diff;
+       unsigned int rem_old, rem_new;
+       unsigned long long res;
 
-       diff = (new >= old) ? new - (new - old) : new + (old - new);
+       res = div_u64_rem(new, 100, &rem_new) * (100 - LAST_AGE_WEIGHT)
+               + div_u64_rem(old, 100, &rem_old) * LAST_AGE_WEIGHT;
 
-       return div_u64(diff * LAST_AGE_WEIGHT, 100);
+       if (rem_new)
+               res += rem_new * (100 - LAST_AGE_WEIGHT) / 100;
+       if (rem_old)
+               res += rem_old * LAST_AGE_WEIGHT / 100;
+
+       return res;
 }
 
 /* This returns a new age and allocated blocks in ei */