Re: [PATCH] f2fs: discard small invalid blocks in current active segments

[Yunlong Song]

How? Can the invalid blocks of file A be discarded, if file B is alive 
all the time and fggc_threshold is 507 ?

On 2017/8/28 17:59, Chao Yu wrote:
> On 2017/8/26 20:49, Yunlong Song wrote:
> > 1. write file A with 5 blocks to current empty active segment
> > 2. remove file A
> > 3. write checkpoint
> > 4. write file B with 507 blocks to the same active segment
> >
> > If file B is alive all the time, the blocks used by file A will never be
> > discarded. So current active segment should also be treated as a candidate
> > for small discards.
> I don't think that would be a big issue, since there will not be any freezing
> log headers, once log header moves, later invalid blocks could be discarded.
>
> Thanks,
>
> > Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
> > ---
> >   fs/f2fs/segment.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 8375257..a2e7c8f 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1339,7 +1339,9 @@ static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
> >   		return false;
> >   
> >   	if (!force) {
> > -		if (!test_opt(sbi, DISCARD) || !se->valid_blocks ||
> > +		if (!test_opt(sbi, DISCARD) ||
> > +			(!se->valid_blocks &&
> > +			!IS_CURSEG(sbi, cpc->trim_start)) ||
> >   			SM_I(sbi)->dcc_info->nr_discards >=
> >   				SM_I(sbi)->dcc_info->max_discards)
> >   			return false;
>
> .

--
Thanks,
Yunlong Song