[f2fs-dev] [PATCH] f2fs: use multiplication instead of division in sanity_check_raw_super

[f2fs-dev] [PATCH] f2fs: use multiplication instead of division in sanity_check_raw_super

[Liu Song via Linux-f2fs-devel]

From: Liu Song <liu.song11@zte.com.cn>

Use multiplication instead of division and be more
consistent with f2fs_msg output information.

Signed-off-by: Liu Song <liu.song11@zte.com.cn>
---
 fs/f2fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index af58b2cc21b8..eba4c0f9c347 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2489,7 +2489,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
 		return 1;
 	}
 
-	if ((segment_count / segs_per_sec) < total_sections) {
+	if (segment_count < (segs_per_sec * total_sections)) {
 		f2fs_msg(sb, KERN_INFO,
 			"Small segment_count (%u < %u * %u)",
 			segment_count, segs_per_sec, total_sections);
-- 
2.20.1



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Re: [f2fs-dev] [PATCH] f2fs: use multiplication instead of division in sanity_check_raw_super

[Chao Yu]

Hi Song,

On 2019-7-1 21:38, Liu Song via Linux-f2fs-devel wrote:
> From: Liu Song <liu.song11@zte.com.cn>
> 
> Use multiplication instead of division and be more
> consistent with f2fs_msg output information.
> 
> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> ---
>  fs/f2fs/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index af58b2cc21b8..eba4c0f9c347 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2489,7 +2489,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
>  		return 1;
>  	}
>  
> -	if ((segment_count / segs_per_sec) < total_sections) {

I think we use division intentionally to avoid potential overflow when doing
multiplication.

You can see the detailed commit message in below fixing patch:

0cfe75c5b011 ("f2fs: enhance sanity_check_raw_super() to avoid potential overflows")

Thanks,

> +	if (segment_count < (segs_per_sec * total_sections)) {
>  		f2fs_msg(sb, KERN_INFO,
>  			"Small segment_count (%u < %u * %u)",
>  			segment_count, segs_per_sec, total_sections);
> 


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Re: [f2fs-dev] [PATCH] f2fs: use multiplication instead of division in sanity_check_raw_super

[fishland via Linux-f2fs-devel]

Hi Chao,

Thanks for your reply, I understand why there can't use multiplication, thanks a lot :D

Best regards
Liu Song

>Hi Song,
>
>On 2019-7-1 21:38, Liu Song via Linux-f2fs-devel wrote:
>> From: Liu Song <liu.song11@zte.com.cn>
>> 
>> Use multiplication instead of division and be more
>> consistent with f2fs_msg output information.
>> 
>> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
>> ---
>>  fs/f2fs/super.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index af58b2cc21b8..eba4c0f9c347 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -2489,7 +2489,7 @@ static int sanity_check_raw_super(struct f2fs_sb_info *sbi,
>>    return 1;
>>   }
>>  
>> - if ((segment_count / segs_per_sec) < total_sections) {
>
>I think we use division intentionally to avoid potential overflow when doing
>multiplication.
>
>You can see the detailed commit message in below fixing patch:
>
>0cfe75c5b011 ("f2fs: enhance sanity_check_raw_super() to avoid potential overflows")
>
>Thanks,
>
>> + if (segment_count < (segs_per_sec * total_sections)) {
>>    f2fs_msg(sb, KERN_INFO,
>>     "Small segment_count (%u < %u * %u)",
>>     segment_count, segs_per_sec, total_sections);
>> 

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