linux-kernel - Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in copy_mc_to

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Date:   Fri, 22 Apr 2022 19:45:31 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Tong Tiangen <tongtiangen@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Robin Murphy <robin.murphy@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Kefeng Wang <wangkefeng.wang@...wei.com>,
        Xie XiuQi <xiexiuqi@...wei.com>,
        Guohanjun <guohanjun@...wei.com>,
        Tong Tiangen <tongtiangen@...wei.com>
Subject: Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in
 copy_mc_to_user

Tong Tiangen <tongtiangen@...wei.com> writes:
> x86/powerpc has it's implementation of copy_mc_to_user but not use #define
> to declare.
>
> This may cause problems, for example, if other architectures open
> CONFIG_ARCH_HAS_COPY_MC, but want to use copy_mc_to_user() outside the
> architecture, the code add to include/linux/uaddess.h is as follows:
>
>     #ifndef copy_mc_to_user
>     static inline unsigned long __must_check
>     copy_mc_to_user(void *dst, const void *src, size_t cnt)
>     {
> 	    ...
>     }
>     #endif
     
The above doesn't exist yet, you add it in patch 3, which is a little
confusing for a reader of this commit in isolation.

I think you could safely move that into this patch, and then this patch
would be ~= "Add generic fallback version of copy_mc_to_user()".

It's probably not worth doing a whole new version of the series just for
that, but if you need to do a new version for some other reason I think
it would be cleaner to introduce the fallback in this commit.

> Then this definition will conflict with the implementation of x86/powerpc
> and cause compilation errors as follow:
>
> Fixes: ec6347bb4339 ("x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()")
> Signed-off-by: Tong Tiangen <tongtiangen@...wei.com>
> ---
>  arch/powerpc/include/asm/uaccess.h | 1 +

Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers