Re: [PATCH] erofs: fix compacted_2b if compacted_4b_initial > totalidx

Yue Hu
2021-09-14T04:57:49Z

On Tue, 14 Sep 2021 12:37:14 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> On Tue, Sep 14, 2021 at 11:59:15AM +0800, Yue Hu wrote:
> > From: Yue Hu <huyue2@yulong.com>
> >
> > Currently, the whole indexes will only be compacted 4B if
> > compacted_4b_initial > totalidx. So, the calculated compacted_2b
> > is worthless for that case. It may waste CPU resources.
> >
> > No need to update compacted_4b_initial as mkfs since it's used to
> > fulfill the alignment of the 1st compacted_2b pack and would handle
> > the case above.
> >
> > We also need to clarify compacted_4b_end here. It's used for the
> > last lclusters which aren't fitted in the previous compacted_2b
> > packs.
> >
> > Some messages are from Xiang.
> >
> > Signed-off-by: Yue Hu <huyue2@yulong.com>
>
> Looks good to me,
> Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
>
> (although I think the subject title would be better changed into
> "clear compacted_2b if compacted_4b_initial > totalidx"

Yeah, 'clear' is much better for this change.

Thanks.

> since 'fix'-likewise words could trigger some AI bot for stable
> kernel backporting..)
>
> Thanks,
> Gao Xiang
>
> > ---
> > fs/erofs/zmap.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> > index 9fb98d8..aeed404 100644
> > --- a/fs/erofs/zmap.c
> > +++ b/fs/erofs/zmap.c
> > @@ -369,7 +369,8 @@ static int compacted_load_cluster_from_disk(struct z_erofs_maprecorder *m,
> > if (compacted_4b_initial == 32 / 4)
> > compacted_4b_initial = 0;
> >
> > - if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
> > + if ((vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B) &&
> > + compacted_4b_initial <= totalidx) {
> > compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
> > else
> > compacted_2b = 0;
> > --
> > 1.9.1