Re: [PATCH] erofs-utils: do not check ->idata_size for compressed files in erofs_prepare_inode_buffer()

[Yue Hu <zbestahu@163.com>]

On Thu, 17 Jun 2021 18:14:17 +0800
Yue Hu <zbestahu@gmail.com> wrote:

> On Thu, 17 Jun 2021 17:30:26 +0800
> Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> 
> > On Thu, Jun 17, 2021 at 05:27:33PM +0800, Gao Xiang wrote:  
> > > On Thu, Jun 17, 2021 at 05:15:55PM +0800, Yue Hu wrote:    
> > > > On Thu, 17 Jun 2021 17:04:29 +0800
> > > > Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> > > >     
> > > > > Hi Yue,
> > > > > 
> > > > > On Thu, Jun 17, 2021 at 04:29:54PM +0800, Yue Hu wrote:    
> > > > > > From: Yue Hu <huyue2@yulong.com>
> > > > > > 
> > > > > > erofs_write_compressed_file() will always set inode->idata_size = 0
> > > > > > if succeed, that means no tail-end data for compressed files. So, no
> > > > > > need to call erofs_prepare_tail_block() which is used to handle
> > > > > > tail-end data for that case. Just skip it.      
> > > > > 
> > > > > Thanks for the patch, due to somewhat long time so I don't quite
> > > > > remember the exact logic here now...
> > > > > 
> > > > > Yet from the description before, it's not strictly correct
> > > > > since my original intention would be to support tail-packing
> > > > > inline compressed data which is similar to uncompressed case
> > > > > to decrease tail extent I/O and save more space.    
> > > > 
> > > > nice.
> > > >     
> > > > > 
> > > > > BTW, if you have some interest, would you like to implement it? :)    
> > > > 
> > > > I don't know if i can finish it. But i would like to have a try :)    
> > > 
> > > My rough thought is to try to inline the last tail compresseed
> > > extent after the on-disk compressed extents, maybe we could let
> > > it work for non-compact (legacy) compress index format cases...    
> > 
> > I mean try to implement non-compact (legacy) compress index format cases
> > first.

I'm trying to do it under 4.19 code (since i have no 5.x environment temporarily).

Now, i think mkfs should be done. But, kernel side seems not working fine(no crash,
no decompression warning/bug). Only some files are working, others not. I'm sure i
can catch the inline data correctly via file dump. And I'm trying debug the issue.
Maybe i need more time to read/understand more decompression code related.

BTW, now i understand no need to go z_erofs_vle_work_xxx for inline part(cur-end)
, just go next_part after mapping as below, am i right? 

Thanks.
  
> 
> Ok, let me try to implement it.
> 
> Thanks.
> 
> >   
> > > 
> > > Yeah, if you have extra time and interest, more ideas / thoughts /
> > > discussions are always welcomed ;)
> > > 
> > > Thanks,
> > > Gao Xiang
> > > 
> > >     
> > > > 
> > > > Thanks.
> > > >     
> > > > > 
> > > > > Thanks,
> > > > > Gao Xiang
> > > > >     
> > > > > > 
> > > > > > Also, correct 'a inode' -> 'an inode'.
> > > > > > 
> > > > > > Signed-off-by: Yue Hu <huyue2@yulong.com>
> > > > > > ---
> > > > > >  lib/inode.c | 4 ++--
> > > > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > > 
> > > > > > diff --git a/lib/inode.c b/lib/inode.c
> > > > > > index b6108db..b5f66de 100644
> > > > > > --- a/lib/inode.c
> > > > > > +++ b/lib/inode.c
> > > > > > @@ -111,7 +111,7 @@ struct erofs_dentry *erofs_d_alloc(struct erofs_inode *parent,
> > > > > >  	return d;
> > > > > >  }
> > > > > >  
> > > > > > -/* allocate main data for a inode */
> > > > > > +/* allocate main data for an inode */
> > > > > >  static int __allocate_inode_bh_data(struct erofs_inode *inode,
> > > > > >  				    unsigned long nblocks)
> > > > > >  {
> > > > > > @@ -572,11 +572,11 @@ static int erofs_prepare_inode_buffer(struct erofs_inode *inode)
> > > > > >  		int ret;
> > > > > >  
> > > > > >  		inode->datalayout = EROFS_INODE_FLAT_PLAIN;
> > > > > > -noinline:
> > > > > >  		/* expend an extra block for tail-end data */
> > > > > >  		ret = erofs_prepare_tail_block(inode);
> > > > > >  		if (ret)
> > > > > >  			return ret;
> > > > > > +noinline:
> > > > > >  		bh = erofs_balloc(INODE, inodesize, 0, 0);
> > > > > >  		if (IS_ERR(bh))
> > > > > >  			return PTR_ERR(bh);
> > > > > > -- 
> > > > > > 1.9.1