Re: [PATCH 1/2 v2] f2fs: fix a missing discard prefree segments

[Chao Yu <yuchao0@huawei.com>]

On 2016/12/21 10:02, Chao Yu wrote:
> Hi Jaegeuk, Yunlei,
> 
> On 2016/12/20 11:11, Yunlei He wrote:
>> If userspace issue a fstrim with a range not involve prefree segments,
>> it will reuse these segments without discard. This patch fix it.
> 
>>From v1 patch, I guess originally Yunlei wants to skip clearing prefree segments
> which is not be included in fstrim range, now v2 patch doesn't follow the
> original intention.
> 
> So I guess below modification is enough:
> 
> -		if (force || !test_opt(sbi, DISCARD))
> +		if (!test_opt(sbi, DISCARD))
> 
> Only we should consider is whether we would send redundant discards though
> fstrim when small discard is on.

Oh, below condition has handling redundant case, sorry for my wrong understanding.

if (force && start * sbi->blocks_per_seg >= cpc->trim_start &&
	end * sbi->blocks_per_seg <= cpc->trim_end)
		continue;

But should fix end boundary judegment as below:
(end - 1) * sbi->blocks_per_seg <= cpc->trim_end

Thanks,

> 
> Thoughts?
> 
>>
>> Signed-off-by: Yunlei He <heyunlei@huawei.com>
>> ---
>>  fs/f2fs/segment.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index 0738f48..a40a34b 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -916,7 +916,11 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>  
>>  		dirty_i->nr_dirty[PRE] -= end - start;
>>  
>> -		if (force || !test_opt(sbi, DISCARD))
>> +		if (!test_opt(sbi, DISCARD))
>> +			continue;
>> +
>> +		if (force && start * sbi->blocks_per_seg >= cpc->trim_start &&
>> +						end * sbi->blocks_per_seg <= cpc->trim_end)
>>  			continue;
>>  
>>  		if (!test_opt(sbi, LFS) || sbi->segs_per_sec == 1) {
>>


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