Re: [f2fs-dev] [PATCH v3] f2fs: avoid fi->i_gc_rwsem[WRITE] lock in f2fs_gc

[Chao Yu <yuchao0@huawei.com>]

Hi Jaegeuk,

Please add:

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

On 2018/8/10 9:46, Jaegeuk Kim wrote:
> On 08/10, Chao Yu wrote:
>> On 2018/8/10 3:59, Jaegeuk Kim wrote:
>>> Yup, how about this?
>>>
>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>> index d816c328f02b..cb510fb36523 100644
>>> --- a/fs/f2fs/gc.c
>>> +++ b/fs/f2fs/gc.c
>>> @@ -1052,6 +1052,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>>  		.iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
>>>  	};
>>>  	unsigned long long last_skipped = sbi->skipped_atomic_files[FG_GC];
>>> +	unsigned long long first_skipped;
>>>  	unsigned int skipped_round = 0, round = 0;
>>>  
>>>  	trace_f2fs_gc_begin(sbi->sb, sync, background,
>>> @@ -1064,8 +1065,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>>  				prefree_segments(sbi));
>>>  
>>>  	cpc.reason = __get_cp_reason(sbi);
>>> -	sbi->skipped_gc_rwsem = 0;
>>>  gc_more:
>>> +	sbi->skipped_gc_rwsem = 0;
>>> +	first_skipped = last_skipped;
>>> +
>>>  	if (unlikely(!(sbi->sb->s_flags & SB_ACTIVE))) {
>>>  		ret = -EINVAL;
>>>  		goto stop;
>>> @@ -1126,8 +1129,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>>>  			goto gc_more;
>>>  		}
>>>  
>>> -		if (sbi->skipped_atomic_files[FG_GC] == last_skipped &&
>>> -				sbi->skipped_atomic_files[FG_GC] >
>>> +		if (first_skipped < last_skipped &&
>>> +				(last_skipped - first_skipped) >
>>
>> IMO, it would be better to judge the condition with skipped number in all round
>> of FGGC instead of last round, since number in last round may not very accurate.
> 
> Yup, moved before gc_more.
> 
>>
>> Thoughts?
>>
>> Thanks,
>>
>>>  						sbi->skipped_gc_rwsem) {
>>>  			f2fs_drop_inmem_pages_all(sbi, true);
>>>  			segno = NULL_SEGNO;
>>>
>>> .
>>>
> 
> .
>