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

[Gao Xiang <xiang@kernel.org>]

On Mon, Aug 17, 2026 at 05:47:24PM +0800, Gao Xiang wrote:
> On Mon, Aug 17, 2026 at 11:21:33AM +0200, Geert Uytterhoeven wrote:
> > Hi Gao,
> > 
> > On Mon, 17 Aug 2026 at 11:05, Gao Xiang <xiang@kernel.org> wrote:
> > > On Mon, Aug 17, 2026 at 10:43:34AM +0200, Geert Uytterhoeven wrote:
> > > > > > > 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..
> > > > > >
> > > > > > It causes more churn (defconfig updates), and makes the defconfig
> > > > > > files larger than needed.
> > > > >
> > > > > Could you submit a formal patch directly (since you found it and
> > > > > suggested a version)?
> > > > >
> > > > > so I could submit it along with the pull request if you're fine with it.
> > > >
> > > > Will do, I want to do a bit more testing first...
> > >
> > > Ok, anyway, I will try to submit a PR hours later.
> > > if there is a patch, the worst case is that it's included in
> > > the follow-up pull request.
> > >
> > > > In addition, usability can be improved by hiding the prompt on UP
> > > > systems:
> > > >
> > > > -       int "EROFS LZMA default maximum decompression streams"
> > > > +       int "EROFS LZMA default maximum decompression streams" if SMP
> > > >
> > >
> > > I hope CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS is a user-visible
> > > configuration (and the Kconfig text helps too) no matter the platform
> > > is UP or not (but it can be omitted in .config) even there is the only
> > > one choice in menuconfig for example on UP platforms.
> > 
> > Why do you prefer it to be a user-visible option on UP?
> > In general, we try not to bother the user with questions about
> > configuration options that do not matter for him, or that offer only
> > a single valid answer.
> > 
> > IMHO even "if SMP && EXPERT" would make sense...
> 
> I think users should not be bothered with !SMP in the beginning.
> 
> CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS impacts the default
> LZMA maximum memory usage, I hope it shows the same for both SMP or
> !SMP (even it cannot be configured on !SMP, since it clearly shows
> to users the number and indicates how the default LZMA stream
> derives in general.)
> 
> I think it's unlike something that is totally disabled in !SMP (or
> does't have such functionality in SMP), I think that is more sense
                                    ^ !SMP

> to hide it in the configuration but here the DEFAULT_MAX_STREAM is still
> meaningful and is 1.

In other words, if NR_CPUS is defined unconditionally (regardless of
SMP or not like the current status), from the user perspective, I
think SMP inclusion here has no real gain, and it should be just
`range 1 NR_CPUS` simply as a unique per-fs configuration.

Thanks,
Gao Xiang

> 
> Thanks,
> Gao Xiang
> 
> > 
> > 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
> > 
>