lwext4_fs test fail on ftruncate()

Josef Söntgen josef.soentgen at genode-labs.com
Thu Jan 13 13:35:54 CET 2022

Hello Alexander,

> I am trying to run lwext4_fs.run from world repo
> it gives the following error on linux/x86_64
> ...
> [init -> test-libc_vfs] calling open(file_name4, O_CREAT | O_WRONLY) file_name=test4.tst
> [init -> test-libc_vfs] open(file_name4, O_CREAT | O_WRONLY) succeeded
> [init -> test-libc_vfs] calling ftruncate(fd, 100)
> [init -> test-libc_vfs] ftruncate(fd, 100) succeeded
> [init -> test-libc_vfs] calling close(fd)
> [init -> test-libc_vfs] close(fd) succeeded
> [init -> test-libc_vfs] calling stat(file_name4, &stat_buf) file_name=test4.tst
> [init -> test-libc_vfs] stat(file_name4, &stat_buf) failed, ret=0, errno=2
> [init -> test-libc_vfs] Error: Uncaught exception of type 'Test_failed'
> [init -> test-libc_vfs] Warning: abort called - thread: ep
> ^Cmake: *** [Makefile:396: run/lwext4_fs] Error 130
> can this error could be ignored?
> is lwext4 port somhow usable in general on 21.11? 

Increasing a file via truncation is not supported by this version of
the lwext4 library (I have not checked if this is addressed upstream by
now). If your use-case depends on this feature, e.g. sparse files,
'lwext4_fs' cannot be used (also, 'cp(1)' from coreutils assumes it may
use lseek/ftruncate to prevent unncessary I/O which will not work either).

> can I utilise it as a main fs inside genode to store compilation
> results in rw mode?

I would recommend sticking to 'vfs/rump' for now as 'lwext4_fs' is not that
well tested.

*Iff* you are fine with debugging problems that arise from using
it I suggest you rather take a look at 'vfs/lwext4' [1] as starting point
because most file-system servers besides the 'vfs' component are on their
way out.

[1] https://github.com/genodelabs/genode-world/issues/278

Regards Josef

Josef Söntgen
Genode Labs

http://www.genode-labs.com/ · http://genode.org/
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