On 2018/4/20 11:40, Jaegeuk Kim wrote:
> On 04/20, Chao Yu wrote:
>> On 2018/4/20 11:26, Jaegeuk Kim wrote:
>>> On 04/20, heyunlei wrote:
>>>>
>>>>
>>>>> -----Original Message-----
>>>>> From: Yuchao (T)
>>>>> Sent: Friday, April 13, 2018 9:12 AM
>>>>> To: Jaegeuk Kim; heyunlei
>>>>> Cc: [email protected]; Wangbintian; Zhangdianfang
>>>>> (Euler)
>>>>> Subject: Re: [f2fs-dev][PATCH v2] f2fs: use cur_map instead of ckpt_map
>>>>>
>>>>> On 2018/4/13 6:37, Jaegeuk Kim wrote:
>>>>>> On 04/10, Yunlei He wrote:
>>>>>>> In flush_sit_entries::add_discard_addrs path, cur_map and ckpt_map
>>>>>>> are the same, but in exist_trim_candidates::add_discard_addrs,
>>>>>>> cur_map is updated one, and newer than ckpt_map, so we need to use
>>>>>>> cur_map to check whether there are discard candidates.
>>>>>>>
>>>>>>> v1->v2: one problem of check discard candidates reported by Chao,
>>>>>>> besides, update commit message.
>>>>>>>
>>>>>>> Signed-off-by: Yunlei He <[email protected]>
>>>>>>> ---
>>>>>>> fs/f2fs/segment.c | 2 +-
>>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>>>> index 5854cc4..f5d0499 100644
>>>>>>> --- a/fs/f2fs/segment.c
>>>>>>> +++ b/fs/f2fs/segment.c
>>>>>>> @@ -1559,7 +1559,7 @@ static bool add_discard_addrs(struct f2fs_sb_info
>>>>>>> *sbi, struct cp_control *cpc,
>>>>>>>
>>>>>>> /* SIT_VBLOCK_MAP_SIZE should be multiple of sizeof(unsigned
>>>>>>> long) */
>>>>>>> for (i = 0; i < entries; i++)
>>>>>>> - dmap[i] = force ? ~ckpt_map[i] & ~discard_map[i] :
>>>>>>> + dmap[i] = force ? ~cur_map[i] & ~discard_map[i] :
>>>>>>
>>>>>> NAK. We're able to loose data for roll-forward recovery.
>>>> Ping
>>>>
>>>> Thanks.
>>>>>
>>>>> Actually, in fstrim flow (force == 1), cur_map is complete the same as
>>>>> ckpt_map.
>>>>> Do you suffer data corruption during testing this patch?
>>>
>>> So, we don't need this patch, IIUC.
>>
>> No, in precheck flow, we haven't flush cur_map to ckpt_map, so they are
>> different.
>
> Then, what if power-cut happens between exist_trim_candidates() and
> do_checkpoint()?
For example:
1. write data block to block address #N
2. write checkpoint cur_map:1, ckpt_map:1
3. punch data block in block address #N cur_map:0, ckpt_map:1
4. call fstrim with range [0, X], X > N
5. exist_trim_candidates should check cur_map to decide whether we need a
checkpoint and further discard? otherwise we will fail to trim suitable
candidates?
I have one other question:
Discard should be issued after a checkpoint, right? except below codes:
if (NM_I(sbi)->dirty_nat_cnt == 0 &&
SIT_I(sbi)->dirty_sentries == 0 &&
prefree_segments(sbi) == 0) {
flush_sit_entries(sbi, cpc);
clear_prefree_segments(sbi, cpc);
unblock_operations(sbi);
goto out;
}
Why can we call flush_sit_entries & clear_prefree_segments without checkpoint?
Thanks,
>
>>
>> - fstrim
>> - exist_trim_candidates
>> - add_discard_addrs
>>
>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>>> (cur_map[i] ^ ckpt_map[i]) &
>>>>>>> ckpt_map[i];
>>>>>>>
>>>>>>> while (force || SM_I(sbi)->dcc_info->nr_discards <=
>>>>>>> --
>>>>>>> 1.9.1
>>>>>>
>>>>>> .
>>>>>>
>>>
>>> .
>>>
>
> .
>
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