Re: [f2fs-dev] [PATCH 10/10] f2fs: return fs_trim if there is no candidate

[Chao Yu <yuchao0@xxxxxxxxxx>]

On 2016/12/31 2:51, Jaegeuk Kim wrote:
> If there is no candidate to submit discard command during f2sf_trim_fs, let's
> return without checkpoint.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>

Please see comments below.

> ---
>  fs/f2fs/checkpoint.c |  5 +++++
>  fs/f2fs/f2fs.h       |  1 +
>  fs/f2fs/segment.c    | 28 +++++++++++++++++++++++-----
>  3 files changed, 29 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 917b5c5053ae..ccea40763d9d 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1249,6 +1249,11 @@ int write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  
>  	/* this is the case of multiple fstrims without any changes */
>  	if (cpc->reason == CP_DISCARD) {
> +		if (!exist_trim_candidates(sbi, cpc)) {
> +			unblock_operations(sbi);
> +			goto out;
> +		}
> +
>  		if (NM_I(sbi)->dirty_nat_cnt == 0 &&
>  				SIT_I(sbi)->dirty_sentries == 0 &&
>  				prefree_segments(sbi) == 0) {
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index f2f40fce9d31..04d113f0d6bf 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2119,6 +2119,7 @@ void release_discard_addrs(struct f2fs_sb_info *);
>  int npages_for_summary_flush(struct f2fs_sb_info *, bool);
>  void allocate_new_segments(struct f2fs_sb_info *);
>  int f2fs_trim_fs(struct f2fs_sb_info *, struct fstrim_range *);
> +bool exist_trim_candidates(struct f2fs_sb_info *, struct cp_control *);
>  struct page *get_sum_page(struct f2fs_sb_info *, unsigned int);
>  void update_meta_page(struct f2fs_sb_info *, void *, block_t);
>  void write_meta_page(struct f2fs_sb_info *, struct page *);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 9a38424c3c1f..82078734f379 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -836,7 +836,8 @@ static void __add_discard_entry(struct f2fs_sb_info *sbi,
>  	SM_I(sbi)->nr_discards += end - start;
>  }
>  
> -static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> +static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
> +							bool check_only)
>  {
>  	int entries = SIT_VBLOCK_MAP_SIZE / sizeof(unsigned long);
>  	int max_blocks = sbi->blocks_per_seg;
> @@ -850,12 +851,12 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  	int i;
>  
>  	if (se->valid_blocks == max_blocks || !f2fs_discard_en(sbi))
> -		return;
> +		return false;
>  
>  	if (!force) {
>  		if (!test_opt(sbi, DISCARD) || !se->valid_blocks ||
>  		    SM_I(sbi)->nr_discards >= SM_I(sbi)->max_discards)
> -			return;
> +			return false;
>  	}
>  
>  	/* SIT_VBLOCK_MAP_SIZE should be multiple of sizeof(unsigned long) */
> @@ -873,8 +874,12 @@ static void add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  					&& (end - start) < cpc->trim_minlen)
>  			continue;
>  
> +		if (check_only)
> +			return true;
> +
>  		__add_discard_entry(sbi, cpc, se, start, end);
>  	}
> +	return false;
>  }
>  
>  void release_discard_addrs(struct f2fs_sb_info *sbi)
> @@ -1455,6 +1460,19 @@ static const struct segment_allocation default_salloc_ops = {
>  	.allocate_segment = allocate_segment_by_default,
>  };
>  
> +bool exist_trim_candidates(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> +{
> +	__u64 trim_start = cpc->trim_start;

bool has_candidate = false;

> +
> +	mutex_lock(&SIT_I(sbi)->sentry_lock);
> +	for (; trim_start <= cpc->trim_end; trim_start++)
> +		if (add_discard_addrs(sbi, cpc, true))
> +			break;

for (; cpc->trim_start <= cpc->trim_end; cpc->trim_start++)
	if (add_discard_addrs(sbi, cpc, true)) {
		has_candidate = true;
		break;
	}

cpc->trim_start = trim_start;

> +	mutex_unlock(&SIT_I(sbi)->sentry_lock);
> +
> +	return trim_start <= cpc->trim_end;

return has_candidate;

Thanks,

> +}
> +
>  int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  {
>  	__u64 start = F2FS_BYTES_TO_BLK(range->start);
> @@ -2251,7 +2269,7 @@ void flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  			/* add discard candidates */
>  			if (cpc->reason != CP_DISCARD) {
>  				cpc->trim_start = segno;
> -				add_discard_addrs(sbi, cpc);
> +				add_discard_addrs(sbi, cpc, false);
>  			}
>  
>  			if (to_journal) {
> @@ -2289,7 +2307,7 @@ void flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  		__u64 trim_start = cpc->trim_start;
>  
>  		for (; cpc->trim_start <= cpc->trim_end; cpc->trim_start++)
> -			add_discard_addrs(sbi, cpc);
> +			add_discard_addrs(sbi, cpc, false);
>  
>  		cpc->trim_start = trim_start;
>  	}
>