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Date: Mon, 9 Mar 2015 15:58:44 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>, Will Drewry <wad@chromium.org>,
        Kees Cook <keescook@chromium.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] move offsetofend() from vfio.h to stddef.h
Message-ID: <20150309145844.GA19511@gmail.com>
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* Denys Vlasenko <dvlasenk@redhat.com> wrote:

> Suggested by Linus.
> 
> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: Ingo Molnar <mingo@kernel.org>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: x86@kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
>  include/linux/stddef.h |  9 +++++++++
>  include/linux/vfio.h   | 13 -------------
>  2 files changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/stddef.h b/include/linux/stddef.h
> index f4aec0e..076af43 100644
> --- a/include/linux/stddef.h
> +++ b/include/linux/stddef.h
> @@ -19,3 +19,12 @@ enum {
>  #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
>  #endif
>  #endif
> +
> +/**
> + * offsetofend(TYPE, MEMBER)
> + *
> + * @TYPE: The type of the structure
> + * @MEMBER: The member within the structure to get the end offset of
> + */
> +#define offsetofend(TYPE, MEMBER) \
> +	(offsetof(TYPE, MEMBER)	+ sizeof(((TYPE *)0)->MEMBER))
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 2d67b89..049b2f4 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -78,19 +78,6 @@ extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
>  extern void vfio_unregister_iommu_driver(
>  				const struct vfio_iommu_driver_ops *ops);
>  
> -/**
> - * offsetofend(TYPE, MEMBER)
> - *
> - * @TYPE: The type of the structure
> - * @MEMBER: The member within the structure to get the end offset of
> - *
> - * Simple helper macro for dealing with variable sized structures passed
> - * from user space.  This allows us to easily determine if the provided
> - * structure is sized to include various fields.
> - */
> -#define offsetofend(TYPE, MEMBER) \
> -	(offsetof(TYPE, MEMBER)	+ sizeof(((TYPE *)0)->MEMBER))

So I like it, and because it is not particularly trivial when to use 
this primitive it was explained nicely in a description in the vfio.h 
version.

But you lost that nice description during the code move!!

Please don't.

Thanks,

	Ingo