[PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Yue Hu]

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.

Signed-off-by: Yue Hu <huyue2@yulong.com>
---
 fs/erofs/zmap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 9fb98d8..4f941b6 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -369,7 +369,10 @@ 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 (compacted_4b_initial > totalidx) {
+		compacted_4b_initial = 0;
+		compacted_2b = 0;
+	} else if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
 		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
 	else
 		compacted_2b = 0;
-- 
1.9.1

Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Gao Xiang]

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.)

So it can be handled in either compacted_4b_initial or compacted_4b_end
cases, because there are all compacted 4B.

Thanks,
Gao Xiang

> 
> Signed-off-by: Yue Hu <huyue2@yulong.com>
> ---
>  fs/erofs/zmap.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> index 9fb98d8..4f941b6 100644
> --- a/fs/erofs/zmap.c
> +++ b/fs/erofs/zmap.c
> @@ -369,7 +369,10 @@ 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 (compacted_4b_initial > totalidx) {
> +		compacted_4b_initial = 0;
> +		compacted_2b = 0;
> +	} else if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
>  		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
>  	else
>  		compacted_2b = 0;
> -- 
> 1.9.1

Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Yue Hu]

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.

Thanks.

> 
> So it can be handled in either compacted_4b_initial or compacted_4b_end
> cases, because there are all compacted 4B.
> 
> Thanks,
> Gao Xiang
> 
> > 
> > Signed-off-by: Yue Hu <huyue2@yulong.com>
> > ---
> >  fs/erofs/zmap.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> > index 9fb98d8..4f941b6 100644
> > --- a/fs/erofs/zmap.c
> > +++ b/fs/erofs/zmap.c
> > @@ -369,7 +369,10 @@ 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 (compacted_4b_initial > totalidx) {
> > +		compacted_4b_initial = 0;
> > +		compacted_2b = 0;
> > +	} else if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
> >  		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
> >  	else
> >  		compacted_2b = 0;
> > -- 
> > 1.9.1  

Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Gao Xiang]

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?

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;
	}

Thanks,
Gao Xiang

> 
> Thanks.
> 
> > 
> > So it can be handled in either compacted_4b_initial or compacted_4b_end
> > cases, because there are all compacted 4B.
> > 
> > Thanks,
> > Gao Xiang
> > 
> > > 
> > > Signed-off-by: Yue Hu <huyue2@yulong.com>
> > > ---
> > >  fs/erofs/zmap.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> > > index 9fb98d8..4f941b6 100644
> > > --- a/fs/erofs/zmap.c
> > > +++ b/fs/erofs/zmap.c
> > > @@ -369,7 +369,10 @@ 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 (compacted_4b_initial > totalidx) {
> > > +		compacted_4b_initial = 0;
> > > +		compacted_2b = 0;
> > > +	} else if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
> > >  		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
> > >  	else
> > >  		compacted_2b = 0;
> > > -- 
> > > 1.9.1  

Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Yue Hu]

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.

Thanks.

> 
> Thanks,
> Gao Xiang
> 
> > 
> > Thanks.
> >   
> > > 
> > > So it can be handled in either compacted_4b_initial or compacted_4b_end
> > > cases, because there are all compacted 4B.
> > > 
> > > Thanks,
> > > Gao Xiang
> > >   
> > > > 
> > > > Signed-off-by: Yue Hu <huyue2@yulong.com>
> > > > ---
> > > >  fs/erofs/zmap.c | 5 ++++-
> > > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> > > > index 9fb98d8..4f941b6 100644
> > > > --- a/fs/erofs/zmap.c
> > > > +++ b/fs/erofs/zmap.c
> > > > @@ -369,7 +369,10 @@ 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 (compacted_4b_initial > totalidx) {
> > > > +		compacted_4b_initial = 0;
> > > > +		compacted_2b = 0;
> > > > +	} else if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
> > > >  		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
> > > >  	else
> > > >  		compacted_2b = 0;
> > > > -- 
> > > > 1.9.1    

Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Gao Xiang]

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;
	}

, 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.

Thanks,
Gao Xiang

> 
> Thanks.

Re: [PATCH] erofs: fix compacted_{4b_initial, 2b} when compacted_4b_initial > totalidx

[Yue Hu]

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.