Re: [PATCH 2/2] Revert "f2fs: add ovp valid_blocks check for bg gc victim to fg_gc"

[Chao Yu <yuchao0@huawei.com>]

Hi Jaegeuk,

Missed this patch, or any problem in it?

Thanks,

On 2018/4/26 17:05, Chao Yu wrote:
> For extreme case:
> 10 section, op = 10%, no_fggc_threshold = 90%
> All section usage: 85% 85% 85% 85% 90% 90% 95% 95% 95% 95%
> 
> During foreground GC, if we skip select dirty section whose usage
> is larger than no_fggc_threshold, we can only recycle 80% invalid
> space from four 85% usage sections and two 90% usage sections,
> result in encountering out-of-space issue.
> 
> This reverts commit e93b9865251a0503d83fd570e7d5a7c8bc351715 to
> fix this issue, besides, we keep the logic that we scan all dirty
> section when searching a victim, so that GC can select victim with
> least valid blocks.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/f2fs/f2fs.h    |  3 ---
>  fs/f2fs/gc.c      | 16 ----------------
>  fs/f2fs/segment.h |  9 ---------
>  3 files changed, 28 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 64e3677998d8..9f8b327272df 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1192,9 +1192,6 @@ struct f2fs_sb_info {
>  	struct f2fs_gc_kthread	*gc_thread;	/* GC thread */
>  	unsigned int cur_victim_sec;		/* current victim section num */
>  
> -	/* threshold for converting bg victims for fg */
> -	u64 fggc_threshold;
> -
>  	/* threshold for gc trials on pinned files */
>  	u64 gc_pin_file_threshold;
>  
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 3134dd781252..62eba4a71123 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -263,10 +263,6 @@ static unsigned int check_bg_victims(struct f2fs_sb_info *sbi)
>  	for_each_set_bit(secno, dirty_i->victim_secmap, MAIN_SECS(sbi)) {
>  		if (sec_usage_check(sbi, secno))
>  			continue;
> -
> -		if (no_fggc_candidate(sbi, secno))
> -			continue;
> -
>  		clear_bit(secno, dirty_i->victim_secmap);
>  		return GET_SEG_FROM_SEC(sbi, secno);
>  	}
> @@ -406,9 +402,6 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
>  			goto next;
>  		if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
>  			goto next;
> -		if (gc_type == FG_GC && p.alloc_mode == LFS &&
> -					no_fggc_candidate(sbi, secno))
> -			goto next;
>  
>  		cost = get_gc_cost(sbi, segno, &p);
>  
> @@ -1152,17 +1145,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  
>  void build_gc_manager(struct f2fs_sb_info *sbi)
>  {
> -	u64 main_count, resv_count, ovp_count;
> -
>  	DIRTY_I(sbi)->v_ops = &default_v_ops;
>  
> -	/* threshold of # of valid blocks in a section for victims of FG_GC */
> -	main_count = SM_I(sbi)->main_segments << sbi->log_blocks_per_seg;
> -	resv_count = SM_I(sbi)->reserved_segments << sbi->log_blocks_per_seg;
> -	ovp_count = SM_I(sbi)->ovp_segments << sbi->log_blocks_per_seg;
> -
> -	sbi->fggc_threshold = div64_u64((main_count - ovp_count) *
> -				BLKS_PER_SEC(sbi), (main_count - resv_count));
>  	sbi->gc_pin_file_threshold = DEF_GC_FAILED_PINNED_FILES;
>  
>  	/* give warm/cold data area from slower device */
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 7702b054689c..c385daabcb67 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -774,15 +774,6 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type)
>  				- (base + 1) + type;
>  }
>  
> -static inline bool no_fggc_candidate(struct f2fs_sb_info *sbi,
> -						unsigned int secno)
> -{
> -	if (get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true) >
> -						sbi->fggc_threshold)
> -		return true;
> -	return false;
> -}
> -
>  static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int secno)
>  {
>  	if (IS_CURSEC(sbi, secno) || (sbi->cur_victim_sec == secno))
>