f2fs: fix overflow when calculating utilization on 32-bit

Changman Lee · Hashcode · commit a78b94ce1e0f · 2016-07-15T00:05:22.000-07:00
Use div_u64 to fix overflow when calculating utilization.
*long int* is 4-bytes on 32-bit so (user blocks * 100) might be
overflow if disk size is over e.g. 512GB.

Signed-off-by: Changman Lee &lt;cm224.lee@samsung.com&gt;
Reviewed-by: Namjae Jeon &lt;namjae.jeon@samsung.com&gt;
Signed-off-by: Jaegeuk Kim &lt;jaegeuk.kim@samsung.com&gt;
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
@@ -464,8 +464,7 @@ static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi, int freed)
 
 static inline int utilization(struct f2fs_sb_info *sbi)
 {
-	return (long int)valid_user_blocks(sbi) * 100 /
-			(long int)sbi->user_block_count;
+	return div_u64(valid_user_blocks(sbi) * 100, sbi->user_block_count);
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -464,8 +464,7 @@ static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi, int freed)`
`464`	`464`
`465`	`465`	`static inline int utilization(struct f2fs_sb_info *sbi)`
`466`	`466`	`{`
`467`		`- return (long int)valid_user_blocks(sbi) * 100 /`
`468`		`- (long int)sbi->user_block_count;`
	`467`	`+ return div_u64(valid_user_blocks(sbi) * 100, sbi->user_block_count);`
`469`	`468`	`}`
`470`	`469`
`471`	`470`	`/*`