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

[Guenter Roeck]

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.

Guenter