linux-kernel - Re: [PATCH] f2fs: discard small invalid blocks in current active segments

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 28 Aug 2017 21:21:29 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     Chao Yu <yuchao0@...wei.com>, <jaegeuk@...nel.org>,
        <chao@...nel.org>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: discard small invalid blocks in current active
 segments

How? Can the invalid blocks of file A be discarded, if file B is alive 
all the time and fggc_threshold is 507 ?

On 2017/8/28 17:59, Chao Yu wrote:
> On 2017/8/26 20:49, Yunlong Song wrote:
>> 1. write file A with 5 blocks to current empty active segment
>> 2. remove file A
>> 3. write checkpoint
>> 4. write file B with 507 blocks to the same active segment
>>
>> If file B is alive all the time, the blocks used by file A will never be
>> discarded. So current active segment should also be treated as a candidate
>> for small discards.
> I don't think that would be a big issue, since there will not be any freezing
> log headers, once log header moves, later invalid blocks could be discarded.
>
> Thanks,
>
>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>> ---
>>   fs/f2fs/segment.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 8375257..a2e7c8f 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -1339,7 +1339,9 @@ static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
>>   		return false;
>>   
>>   	if (!force) {
>> -		if (!test_opt(sbi, DISCARD) || !se->valid_blocks ||
>> +		if (!test_opt(sbi, DISCARD) ||
>> +			(!se->valid_blocks &&
>> +			!IS_CURSEG(sbi, cpc->trim_start)) ||
>>   			SM_I(sbi)->dcc_info->nr_discards >=
>>   				SM_I(sbi)->dcc_info->max_discards)
>>   			return false;
>>
>
> .
>

-- 
Thanks,
Yunlong Song