[RFC v7 21/21] um: nommu: add block device support of UML

[Hajime Tazaki]

On Wed, 07 Oct 2020 23:17:31 +0900,
Anton Ivanov wrote:

> > diff --git a/arch/um/nommu/um/Kconfig b/arch/um/nommu/um/Kconfig
> > index 20b3eaccb6f0..c6a3f472fe75 100644
> > --- a/arch/um/nommu/um/Kconfig
> > +++ b/arch/um/nommu/um/Kconfig
> > @@ -4,6 +4,10 @@ config UML_NOMMU
> >   	select UACCESS_MEMCPY
> >   	select ARCH_THREAD_STACK_ALLOCATOR
> >   	select ARCH_HAS_SYSCALL_WRAPPER
> > +	select VFAT_FS
> > +	select NLS_CODEPAGE_437
> > +	select NLS_ISO8859_1
> > +	select BTRFS_FS
> >     config 64BIT
> >   	bool
> > @@ -35,3 +39,7 @@ config STACKTRACE_SUPPORT
> >   config PRINTK_TIME
> >   	bool
> >   	default y
> > +
> > +config RAID6_PQ_BENCHMARK
> > +	bool
> > +	default n
> 
> Why are we touching this? I thought this is already defined in lib/Kconfig?

With the scheduler which LKL implements, it has the same issue with
what time-travel=inf-cpu has when CONFIG_BTRFS_FS is enable.  I tried
to follow the way of the commit d65197a (below), but if I added
"depends on !RAID6_PQ_BENCHMARK" to config UMMODE_LIB, I got "error:
recursive dependency detected!".

https://github.com/thehajime/linux/commit/d65197ad52494bed3b5e64708281b8295f76c391#diff-c170aa964ad412630a2b5addf306ff14

Thus, to avoid this situation, I did the above additional config
RAID6_PQ_BENCHMARK just for UMMODE_LIB.

I plan to rework on Kconfig (UMMODE_LIB and !MMU) and will figure out
more appropriate way.

-- Hajime