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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Tue, 7 Dec 2021 16:44:47 +0100
Message-ID: <CAK8P3a2gsdbiQoH_82Nm97DeENzJMUZn99m0LHE4Rt-0pd2d6w@mail.gmail.com>
Subject: Re: [RFC 1/3] headers: add more types to linux/types.h
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Guenter Roeck <groeck@chromium.org>,
        Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        kernel test robot <lkp@intel.com>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tejun Heo <tj@kernel.org>, kernelci@groups.io,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        llvm@lists.linux.dev
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On Tue, Dec 7, 2021 at 4:21 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Dec 07, 2021 at 04:09:25PM +0100, Arnd Bergmann wrote:
> > +struct list_lru {
> > +     struct list_lru_node    *node;
> > +#ifdef CONFIG_MEMCG_KMEM
> > +     struct list_head        list;
> > +     int                     shrinker_id;
> > +     bool                    memcg_aware;
> > +#endif
> > +};
>
> This is the only one that gives me qualms.  While there are other
> CONFIG options mentioned in types.h they're properties of the platform,
> eg CONFIG_HAVE_UID16, CONFIG_64BIT, CONFIG_ARCH_DMA_ADDR_T_64BIT, etc.
> I dislike it that changing this CONFIG option is going to result in
> rebuilding the _entire_ kernel.  CONFIG_MEMCG_KMEM just isn't that
> central to how everything works.

I included this one because 'struct list_lru' is used in 'struct
super_block', which I move
into 'linux/fs_types.h' in the third patch. It is otherwise not used a
lot though, and
'struct super_block' is rarely much outside of file system code. If we
leave super_block
in fs.h or in a separate header, it should be fine.

        Arnd