Re: [PATCH] f2fs: add a judgment in add_discard_addrs

[He YunLei <heyunlei@huawei.com>]

On 2015/9/9 9:11, Chao Yu wrote:
>> -----Original Message-----
>> From: He YunLei [mailto:heyunlei@huawei.com]
>> Sent: Wednesday, September 09, 2015 7:54 AM
>> To: Chao Yu
>> Cc: jaegeuk@kernel.org; linux-f2fs-devel@lists.sourceforge.net; bintian.wang@huawei.com
>> Subject: Re: [f2fs-dev] [PATCH] f2fs: add a judgment in add_discard_addrs
>>
>> On 2015/9/8 19:14, Chao Yu wrote:
>>> Hi Yunlei,
>>>
>>>> -----Original Message-----
>>>> From: Yunlei He [mailto:heyunlei@huawei.com]
>>>> Sent: Tuesday, September 08, 2015 6:51 PM
>>>> To: chao2.yu@samsung.com; jaegeuk@kernel.org; linux-f2fs-devel@lists.sourceforge.net
>>>> Cc: bintian.wang@huawei.com; Yunlei He
>>>> Subject: [f2fs-dev] [PATCH] f2fs: add a judgment in add_discard_addrs
>>>>
>>>> CP_DISCARD traverse all segments in fstrim_range to add small discards,
>>>> it is better to select entry->len bigger than trim_minlen.
>>>
>>> If we mount with 'discard' option, f2fs will trigger real-time discard
>>> when do checkpoint. If we add judgment condition here, fragmented invalid
>>> blocks will not be discarded since we stop adding them in pending list
>>> through __add_discard_entry.
>>
>> This judgment condition is only valid for cp reason CP_DISCARD, and has no influence
>> to other checkpoint. The process of fstrim adds all invalid blocks in pending list and
>> deletes entries which len < trim_minlen when issue discard. Can we do the selection
>> when added?
>
> __add_discard_entry will try to merge small discards in pending list, and merged discard
> may be the eligible candidate, so we'd better not skip that.
>
Yeah, I got it. But I think the probability of merge will not be too high.
Thanks,
> Thanks,
>
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Signed-off-by: Yunlei He <heyunlei@huawei.com>
>>>> ---
>>>>    fs/f2fs/segment.c | 3 ++-
>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> index 78e6d06..a0dab7a 100644
>>>> --- a/fs/f2fs/segment.c
>>>> +++ b/fs/f2fs/segment.c
>>>> @@ -599,7 +599,8 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control
>>>> *cpc)
>>>>    			break;
>>>>
>>>>    		end = __find_rev_next_zero_bit(dmap, max_blocks, start + 1);
>>>> -		__add_discard_entry(sbi, cpc, se, start, end);
>>>> +		if(force && cpc->trim_minlen >= (end - start))
>>>> +			__add_discard_entry(sbi, cpc, se, start, end);
>>>>    	}
>>>>    }
>>>>
>>>> --
>>>> 1.9.1
>>>
>>>
>>>
>
>
> .
>


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