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

Saumya Panda saumya.iisc at gmail.com
Mon Jan 20 17:55:15 AEDT 2020


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.

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
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