Re: [PATCH] erofs: fix EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS on some UP platforms

[Gao Xiang <xiang@kernel.org>]

Hi Geert,

On Mon, Aug 17, 2026 at 09:32:51AM +0200, Geert Uytterhoeven wrote:
> Hi Gao,
> 

..

> 
> Thanks for your patch, which is now commit a64d500b0078e16e ("erofs: fix
> EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS on some UP platforms") in v7.2.
> 
> > --- a/fs/erofs/Kconfig
> > +++ b/fs/erofs/Kconfig
> > @@ -134,7 +134,8 @@ config EROFS_FS_ZIP_LZMA
> >  config EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS
> >         int "EROFS LZMA default maximum decompression streams"
> >         depends on EROFS_FS_ZIP_LZMA
> > -       range 1 NR_CPUS
> > +       range 1 NR_CPUS if SMP
> > +       range 1 1 if !SMP
> >         default 16
> 
> I have just discovered another oddity: when you have less than 16
> CPUS (including SMP=n), this default value is invalid, and "make
> savedefconfig" will always write a line like
> 
>     CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS=1
> 
> to the defconfig file, even if that is the default suggested value.
> 
> Needlessly polluting the defconfig files could be fixed using:
> 
>     -       default 16
>     +       default 16 if SMP && NR_CPUS >= 16
>     +       default NR_CPUS if SMP

I guess `default NR_CPUS if SMP && NR_CPUS < 16` would be better,
I'm not sure since I'm not handy in Kconfig stuffs.

>     +       default 1 if !SMP
> 
> Thoughts?

In principle, that would be better, but may I ask if there is some
severe consequences out of one extra line of
CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS=1?

Since it has been fixed for many times, I hope if it could be improved
later if no severe impacts, sigh..

Thanks,
Gao Xiang

> 
> >         help
> >           By default EROFS allocates one LZMA decompression stream per CPU.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
>