linux-kernel - Re: [f2fs-dev] [PATCH 08/10] f2fs: relax async discard commands more

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Date:   Fri, 6 Jan 2017 11:32:36 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH 08/10] f2fs: relax async discard commands more

Hi Jaegeuk,

On 2017/1/6 10:42, Jaegeuk Kim wrote:
> Hi Chao,
> 
> On 01/06, Chao Yu wrote:
>> On 2017/1/6 3:46, Jaegeuk Kim wrote:
>>> On 01/05, Chao Yu wrote:
>>>> On 2017/1/4 17:29, Chao Yu wrote:
>>>>> On 2016/12/31 2:51, Jaegeuk Kim wrote:
>>>>>> This patch relaxes async discard commands to avoid waiting its end_io during
>>>>>> checkpoint.
>>>>>> Instead of waiting them during checkpoint, it will be done when actually reusing
>>>>>> them.
>>>>>>
>>>>>> Test on initial partition of nvme drive.
>>>>>>
>>>>>>  # time fstrim /mnt/test
>>>>>>
>>>>>> Before : 6.158s
>>>>>> After : 4.822s
>>>>>>
>>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>>>>
>>>>> Reviewed-by: Chao Yu <yuchao0@...wei.com>
>>>>>
>>>>> One comment below,
>>>>
>>>> I still have a comment on this patch.
>>>>
>>>>>> -void f2fs_wait_all_discard_bio(struct f2fs_sb_info *sbi)
>>>>>> +/* This should be covered by global mutex, &sit_i->sentry_lock */
>>>>>> +void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, unsigned int segno)
>>>>>>  {
>>>>>>  	struct list_head *wait_list = &(SM_I(sbi)->wait_list);
>>>>>>  	struct bio_entry *be, *tmp;
>>>>>> @@ -646,7 +650,15 @@ void f2fs_wait_all_discard_bio(struct f2fs_sb_info *sbi)
>>>>>>  		struct bio *bio = be->bio;
>>>>>>  		int err;
>>>>>>  
>>>>>> -		wait_for_completion_io(&be->event);
>>>>>> +		if (!completion_done(&be->event)) {
>>>>>> +			if ((be->start_segno >= segno &&
>>>>>> +					be->end_segno <= segno) ||
>>>>>
>>>>> segno >= be->start_segno && segno < be->end_segno ?
>>
>> Still can not understand this judgment condition, we should wait completion of
>> discard command only when segno is locate in range of [start_segno, end_segno]?
>>
>> But now, this condition can be true only when segno, start_segno, end_segno have
>> equal value.
>>
>> Please correct me if I'm wrong.
> 
> Urg. I rewrote it to use block addresses.
> 
> How about this?

Looks good to me. Nice work!

Thanks,