[RFC PATCH v4 2/3] erofs-utils: lib: support on-disk offset for shifted decompression

[Yue Hu]

On Wed, 24 Aug 2022 16:45:59 +0800
Gao Xiang <hsiangkao at linux.alibaba.com> wrote:

> Hi Yue,
> 
> On Sun, Aug 21, 2022 at 09:57:24PM +0800, zbestahu at gmail.com wrote:
> > From: Yue Hu <huyue2 at coolpad.com>
> > 
> > Add support to uncompressed data layout with on-disk offset for
> > compressed files.  
> 
> Sorry for some delay.
> 
> Add interlaced uncompressed data layout for compressed files.
> 
> > 
> > Signed-off-by: Yue Hu <huyue2 at coolpad.com>
> > ---
> >  include/erofs/decompress.h |  3 +++
> >  lib/data.c                 |  8 +++++++-
> >  lib/decompress.c           | 10 ++++++++--
> >  3 files changed, 18 insertions(+), 3 deletions(-)
> > 
> > diff --git a/include/erofs/decompress.h b/include/erofs/decompress.h
> > index 82bf7b8..b622df5 100644
> > --- a/include/erofs/decompress.h
> > +++ b/include/erofs/decompress.h
> > @@ -23,6 +23,9 @@ struct z_erofs_decompress_req {
> >  	unsigned int decodedskip;
> >  	unsigned int inputsize, decodedlength;
> >  
> > +	/* head offset of uncompressed data */
> > +	unsigned int shiftedhead;  
> 
> 	/* cut point of interlaced uncompressed data */
> 	unsigned int interlaced_offset;
> 
> > +
> >  	/* indicate the algorithm will be used for decompression */
> >  	unsigned int alg;
> >  	bool partial_decoding;
> > diff --git a/lib/data.c b/lib/data.c
> > index 2af73c7..008790d 100644
> > --- a/lib/data.c
> > +++ b/lib/data.c
> > @@ -226,7 +226,7 @@ static int z_erofs_read_data(struct erofs_inode *inode, char *buffer,
> >  	};
> >  	struct erofs_map_dev mdev;
> >  	bool partial;
> > -	unsigned int bufsize = 0;
> > +	unsigned int bufsize = 0, head;
> >  	char *raw = NULL;
> >  	int ret = 0;
> >  
> > @@ -307,10 +307,16 @@ static int z_erofs_read_data(struct erofs_inode *inode, char *buffer,
> >  		if (ret < 0)
> >  			break;
> >  
> > +		head = 0;
> > +		if (erofs_sb_has_fragments() &&  
> 
> Can we add another Z_EROFS_ADVISE_ for this, such as
> Z_EROFS_ADVISE_INTERLACED_UNCOMPRESSED_DATA ?

Sounds good, let's do this.

Thanks.

> 
> > +		    map.m_algorithmformat == Z_EROFS_COMPRESSION_SHIFTED)
> > +			head = erofs_blkoff(end);
> > +
> >  		ret = z_erofs_decompress(&(struct z_erofs_decompress_req) {
> >  					.in = raw,
> >  					.out = buffer + end - offset,
> >  					.decodedskip = skip,
> > +					.shiftedhead = head,
> >  					.inputsize = map.m_plen,
> >  					.decodedlength = length,
> >  					.alg = map.m_algorithmformat,
> > diff --git a/lib/decompress.c b/lib/decompress.c
> > index 1661f91..08a0861 100644
> > --- a/lib/decompress.c
> > +++ b/lib/decompress.c
> > @@ -132,14 +132,20 @@ out:
> >  int z_erofs_decompress(struct z_erofs_decompress_req *rq)
> >  {
> >  	if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED) {
> > +		unsigned int count, rightpart;
> > +
> >  		if (rq->inputsize > EROFS_BLKSIZ)
> >  			return -EFSCORRUPTED;
> >  
> >  		DBG_BUGON(rq->decodedlength > EROFS_BLKSIZ);
> >  		DBG_BUGON(rq->decodedlength < rq->decodedskip);
> >  
> > -		memcpy(rq->out, rq->in + rq->decodedskip,
> > -		       rq->decodedlength - rq->decodedskip);
> > +		count = rq->decodedlength - rq->decodedskip;
> > +		rightpart = min(EROFS_BLKSIZ - rq->shiftedhead, count);
> > +
> > +		memcpy(rq->out, rq->in + (erofs_sb_has_fragments() ?  
> 
> same here.
> 
> Thanks,
> Gao Xiang
> 
> > +		       rq->shiftedhead : rq->decodedskip), rightpart);
> > +		memcpy(rq->out + rightpart, rq->in, count - rightpart);
> >  		return 0;
> >  	}
> >  
> > -- 
> > 2.17.1