Problem in EROFS: Not able to read the files after mount

[Gao Xiang]

Hi Saumya,

On Mon, Jan 20, 2020 at 12:25:15PM +0530, Saumya Panda wrote:
> Hi Experts,
>    I am testing EROFS in openSuse(Kernel: 5.4.7-1-default). I used the
> enwik8 and enwik9 as source file (
> https://cs.fit.edu/~mmahoney/compression/textdata.html) for compression.
> But after I mount the erofs image, I am not able to read it (it is saying
> operation not permitted). Simple "ls" command is not working. But if I
> create EROFS image without compression flag, then after mount I am able to
> read the files. Seems there is some problem during compression.
> 
> I will appreciate if someone can help me out why this is happening.

Could you please check if your opensuse kernel has been enabled
the following configuration?

CONFIG_EROFS_FS_ZIP=y
CONFIG_EROFS_FS_CLUSTER_PAGE_LIMIT=1

By default, they should be enabled, but it seems not according to
the following information you mentioned.

Thanks,
Gao Xiang

> 
> Steps followed:
> *Erofs image creation & mount: *
> mkfs.erofs -zlz4hc enwik8.erofs.img enwik8/
> mkfs.erofs 1.0
>         c_version:           [     1.0]
>         c_dbg_lvl:           [       0]
>         c_dry_run:           [       0]
> mount enwik8.erofs.img /mnt/enwik8/ -t erofs -o loop
> 
> ls -l /mnt/enwik8/
> ls: cannot access '/mnt/enwik8/enwik8': Operation not supported
> total 0
> -????????? ? ? ? ?            ? enwik8
> 
> The problem seen for both lz4 & lz4hc.
> 
> *Erofs image creation & mount without compression: *
> mkfs.erofs  enwik8_nocomp.erofs.img enwik8/
> mkfs.erofs 1.0
>         c_version:           [     1.0]
>         c_dbg_lvl:           [       0]
>         c_dry_run:           [       0]
> 
> mount enwik8_nocomp.erofs.img /mnt/enwik8_nocomp/ -t erofs -o loop
> 
> ls -l /mnt/enwik8_nocomp/
> total 97660
> -rw-r--r-- 1 root root 100000000 Jan 20 01:27 enwik8
> 
> *Original enwik8 file:*
> ls -l enwik8
> total 97660
> -rw-r--r-- 1 root root 100000000 Jan 20 01:14 enwik8
> 
> *Source code used for Lz4 and Erofs utils:*
> https://github.com/hsiangkao/erofs-utils
> https://github.com/lz4/lz4
> 
> -- 
> Thanks,
> Saumya Prakash Panda