linux-kernel - [PATCH] f2fs: fix incorrect bimodal calculation

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Message-id: <010701d0f59e$dcc573b0$96505b10$@samsung.com>
Date:	Wed, 23 Sep 2015 09:25:43 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	Jaegeuk Kim <jaegeuk@...nel.org>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: [PATCH] f2fs: fix incorrect bimodal calculation

In update_sit_info, we use div_u64 to handle 'u64 divide u64' case, but
div_u64 can only handle 32-bits divisor, so our divisor with u64 type
passed to div_u64 will overflow, result in the wrong calculation when
show debug info of f2fs as below:

BDF: 464, avg. vblocks: 23509
(BDF should never exceed 100)

So change to use div64_u64 to handle this case correctly.

Signed-off-by: Chao Yu <chao2.yu@...sung.com>
---
 fs/f2fs/debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index ebfcc40..615a307 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -118,7 +118,7 @@ static void update_sit_info(struct f2fs_sb_info *sbi)
 		}
 	}
 	dist = div_u64(MAIN_SECS(sbi) * hblks_per_sec * hblks_per_sec, 100);
-	si->bimodal = div_u64(bimodal, dist);
+	si->bimodal = div64_u64(bimodal, dist);
 	if (si->dirty_count)
 		si->avg_vblocks = div_u64(total_vblocks, ndirty);
 	else
-- 
2.5.2


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