From: Yue Hu <zbestahu@163.com>
To: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: linux-kernel@vger.kernel.org, huyue2@yulong.com,
linux-erofs@lists.ozlabs.org, zhangwen@yulong.com
Subject: Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx
Date: Mon, 13 Sep 2021 20:22:58 +0800 [thread overview]
Message-ID: <20210913202258.356ba284.zbestahu@163.com> (raw)
In-Reply-To: <YT8ztN/F4StUYYNS@B-P7TQMD6M-0146.local>
On Mon, 13 Sep 2021 19:19:16 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> Hi Yue,
>
> On Mon, Sep 13, 2021 at 06:58:36PM +0800, Yue Hu wrote:
> > Hi Xiang,
> >
> > On Mon, 13 Sep 2021 17:11:24 +0800
> > Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> >
> > > On Mon, Sep 13, 2021 at 05:00:16PM +0800, Yue Hu wrote:
> > > > On Mon, 13 Sep 2021 16:48:45 +0800
> > > > Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> > > >
> > > > > Hi Yue,
> > > > >
> > > > > On Mon, Sep 13, 2021 at 03:24:05PM +0800, Yue Hu wrote:
> > > > > > From: Yue Hu <huyue2@yulong.com>
> > > > > >
> > > > > > mkfs.erofs will treat compacted_4b_initial & compacted_2b as 0 if
> > > > > > compacted_4b_initial > totalidx, kernel should be aligned with it
> > > > > > accordingly.
> > > > >
> > > > > There is no difference between compacted_4b_initial or compacted_4b_end
> > > > > for compacted 4B. Since in this way totalidx for compact 2B won't larger
> > > > > than 16 (number of lclusters in a compacted 2B pack.)
> > > >
> > > > However, we can see compacted_2b is a big number for this case. It should
> > > > be pointless.
> > >
> > > Does it has some real impact?
> >
> > No real impact to correct result.
> >
> > >
> > > compacted_4b_initial is only used for the alignment use for the
> > > first compacted_2b so that each compacted_2b pack won't cross
> > > the block (page) boundary. And compacted_4b_end is for the last
> > > lclusters aren't fitted in any compacted_2b pack.
> > >
> > > If compacted_4b_initial > totalidx, I think the whole indexes
> > > would be compacted 4B and handled in
> > >
> > > if (lcn < compacted_4b_initial) {
> > > amortizedshift = 2;
> > > goto out;
> > > }
> >
> > Yes, it is.
> >
> > My point is why we need compacted_2b here for this case. If it's
> > not helpful/used for next code logic, we should remove/avoid it.
> > I think that may cause some misunderstanding and consume unneeded
> > CPU resources.
>
> Okay, make sense. If the number of compacted_2b misleads, how about
> just
>
> if ((vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B) &&
> compacted_4b_initial <= totalidx) {
> compacted_2b = ...;
> } else {
> compacted_2b = 0;
> }
Looks good. So, the patch title may change a little.
>
> , and refine the commit message to point out the following facts for
> other folks:
>
> - compacted_4b_initial is used contain the very first lclusters in order
> to fulfill the alignment of the first compacted_2b pack;
>
> - compacted_4b_end is used for the last lclusters which aren't fitted in
> the previous compacted_2b packs;
>
> - if compacted_4b_initial > totalidx, the whole indexes will be compacted
> 4B and handled with compacted_4b_initial.
Ok, will add these facts above in v2.
Thanks.
>
> Thanks,
> Gao Xiang
>
> >
> > Thanks.
prev parent reply other threads:[~2021-09-13 12:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-13 7:24 [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx Yue Hu
2021-09-13 8:48 ` Gao Xiang
2021-09-13 9:00 ` Yue Hu
2021-09-13 9:11 ` Gao Xiang
2021-09-13 10:58 ` Yue Hu
2021-09-13 11:19 ` Gao Xiang
2021-09-13 12:22 ` Yue Hu [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210913202258.356ba284.zbestahu@163.com \
--to=zbestahu@163.com \
--cc=hsiangkao@linux.alibaba.com \
--cc=huyue2@yulong.com \
--cc=linux-erofs@lists.ozlabs.org \
--cc=linux-kernel@vger.kernel.org \
--cc=zhangwen@yulong.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).