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

[Jaegeuk Kim]

Hi Chao,

On 02/22, Chao Yu wrote:
> 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;
> 	}

Why do we need to do like this in which needs additional variable with multiple
assignment?

Thanks,

> 
> 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;
> >  	}
> > 
> 
> 
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