Re: [PATCH v3] erofs: cap LZMA stream pool size

[Gao Xiang <xiang@kernel.org>]

On Fri, Aug 14, 2026 at 11:44:31AM -0700, Guenter Roeck wrote:
> On 8/14/26 11:26, Gao Xiang wrote:
> > Hi Guenter,
> > 
> > On Wed, Aug 12, 2026 at 07:25:50AM -0700, Guenter Roeck wrote:
> > 
> > ...
> > 
> > > > > 
> > > > > Thank you, that seems to work (despite still seeing the warning on m68k,
> > > > > as NR_CPUS does not exist).
> > > > > 
> > > > 
> > > > ...
> > > > 
> > > > > 
> > > > >         $ make ARCH=m68k allmodconfig
> > > > >        fs/erofs/Kconfig:137:warning: range is invalid
> > > > > 
> > > > >    Warning...
> > > > > 
> > > > 
> > > > Yes, other arches shouldn't have the warning because I think other
> > > > arches (including microblaze) defines NR_CPUS in Kconfig, except m68k.
> > > > 
> > > 
> > > That is not entirely true. openrisc only has it if SMP=y. But it still
> > > does not generate the warning for some reason.
> > > 
> > 
> > I looked into the documentation a bit
> > (https://docs.kernel.org/kbuild/kconfig-language.html), especially the
> > following parts:
> > 
> >   - type definition: “bool”/”tristate”/”string”/”hex”/”int” ...
> >   - input prompt: “prompt” <prompt> [“if” <expr>] ...
> >       and "If a prompt is not present, the config option is
> >            a non-visible symbol, ..."
> > 
> >   - dependencies: “depends on” <expr> [“if” <expr>] ...
> >   - Menu dependencies ..
> > 
> > and I think that is true, taking openrisc for example:
> > 
> > config NR_CPUS
> >          int "Maximum number of CPUs (2-32)"
> >          range 2 32
> >          depends on SMP
> >          default "2"
> > 
> > which can be transformed into
> > 
> > config NR_CPUS
> >          int
> > 	prompt "Maximum number of CPUs (2-32)"
> > 	range 2 32
> > 	depends on SMP
> >          default "2"
> > 
> > which can be then transformed into
> > 
> > config NR_CPUS
> >          int
> > 	prompt "Maximum number of CPUs (2-32)" if SMP
> > 	range 2 32 if SMP
> >          default "2" if SMP
> > 
> > so if `SMP=n`, it's equivalent to
> > 
> > config NR_CPUS
> >          int
> > 
> > so NR_CPUS symbol is still there I think (and its value is 0.)
> > 
> $ grep NR_CPUS .config
> CONFIG_FORCE_NR_CPUS=y
> $ grep EROFS .config
> CONFIG_EROFS_FS=y
> # CONFIG_EROFS_FS_DEBUG is not set
> CONFIG_EROFS_FS_XATTR=y
> CONFIG_EROFS_FS_POSIX_ACL=y
> CONFIG_EROFS_FS_SECURITY=y
> CONFIG_EROFS_FS_BACKED_BY_FILE=y
> CONFIG_EROFS_FS_ZIP=y
> CONFIG_EROFS_FS_ZIP_LZMA=y
> CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS=0
> # CONFIG_EROFS_FS_ZIP_DEFLATE is not set
> # CONFIG_EROFS_FS_ZIP_ZSTD is not set
> # CONFIG_EROFS_FS_ZIP_ACCEL is not set
> # CONFIG_EROFS_FS_PCPU_KTHREAD is not set
> # CONFIG_EROFS_FS_PAGE_CACHE_SHARE is not set
> 
> The symbol may be there internally, but it does not show up in .config.

As I said, the documentation:

If a prompt is not present, the config option is
a non-visible symbol, meaning its value cannot be
directly changed by the user (such as altering the
value in .config) and the option will not appear in
any config menus.

So It think it's expected, and any config X like
this won't be shown in .config:

config X
	int

Thanks,
Gao Xiang

> 
> Guenter
> 
>