linux-kernel - Re: [PATCH v3 13/21] kexec: allocate vmcoreinfo note buffer on page-size boundary

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Date:	Tue, 19 Mar 2013 15:12:48 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	vgoyal@...hat.com, cpw@....com, kumagai-atsushi@....nes.nec.co.jp,
	lisa.mitchell@...com, heiko.carstens@...ibm.com,
	akpm@...ux-foundation.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, zhangyanfei@...fujitsu.com
Subject: Re: [PATCH v3 13/21] kexec: allocate vmcoreinfo note buffer on page-size boundary

HATAYAMA Daisuke <d.hatayama@...fujitsu.com> writes:

> To satisfy mmap()'s page-size boundary requirement, specify aligned
> attribute to vmcoreinfo_note objects to allocate it on page-size
> boundary.

Those requirements don't exist.  Making this patch wasteful and wrong.

Eric

> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
> ---
>
>  include/linux/kexec.h |    6 ++++--
>  kernel/kexec.c        |    2 +-
>  2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index d2e6927..5113570 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -185,8 +185,10 @@ extern struct kimage *kexec_crash_image;
>  #define VMCOREINFO_BYTES           (4096)
>  #define VMCOREINFO_NOTE_NAME       "VMCOREINFO"
>  #define VMCOREINFO_NOTE_NAME_BYTES ALIGN(sizeof(VMCOREINFO_NOTE_NAME), 4)
> -#define VMCOREINFO_NOTE_SIZE       (KEXEC_NOTE_HEAD_BYTES*2 + VMCOREINFO_BYTES \
> -				    + VMCOREINFO_NOTE_NAME_BYTES)
> +#define VMCOREINFO_NOTE_SIZE       ALIGN(KEXEC_NOTE_HEAD_BYTES*2	\
> +					 +VMCOREINFO_BYTES		\
> +					 +VMCOREINFO_NOTE_NAME_BYTES,	\
> +					 PAGE_SIZE)
>  
>  /* Location of a reserved region to hold the crash kernel.
>   */
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index d1f365e..195de6d 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -43,7 +43,7 @@ note_buf_t __percpu *crash_notes;
>  
>  /* vmcoreinfo stuff */
>  static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
> -u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
> +u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4] __aligned(PAGE_SIZE);
>  size_t vmcoreinfo_size;
>  size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
>  
--
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