linux-kernel - Re: [PATCH 1/2] sysfs: Add crash_notes

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Date:	Fri, 29 Mar 2013 11:50:35 +0800
From:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
To:	Simon Horman <horms@...ge.net.au>
CC:	Greg KH <gregkh@...uxfoundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, vgoyal@...hat.com,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] sysfs: Add crash_notes_size to export percpu note
 size

Hi, simon

I forgot to add your email in the CC, could you please help
reviewing this patch since I will send the kexec-tools patch
if this patch is accepted.

Thanks
Zhang

于 2013年03月28日 16:15, Zhang Yanfei 写道:
> For percpu notes, we are exporting only address and not size. So
> the userspace tool kexec-tools is putting an upper limit of 1024
> and putting the value in p_memsz and p_filesz fields. So the patch
> add the new sysfile crash_notes_size to export the exact percpu
> note size and let the kexec-tools parse it intead of using 1024.
> 
> The idea came from Vivek Goyal. And a later patch will be sent to
> kexec-tools to let it parse the size.
> 
> Cc: Greg KH <gregkh@...uxfoundation.org>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Signed-off-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
> ---
>  drivers/base/cpu.c |   14 ++++++++++++++
>  1 files changed, 14 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index fb10728..a55b590 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -132,6 +132,17 @@ static ssize_t show_crash_notes(struct device *dev, struct device_attribute *att
>  	return rc;
>  }
>  static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
> +
> +static ssize_t show_crash_notes_size(struct device *dev,
> +				     struct device_attribute *attr,
> +				     char *buf)
> +{
> +	ssize_t rc;
> +
> +	rc = sprintf(buf, "%lu\n", sizeof(note_buf_t));
> +	return rc;
> +}
> +static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
>  #endif
>  
>  /*
> @@ -259,6 +270,9 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
>  #ifdef CONFIG_KEXEC
>  	if (!error)
>  		error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
> +	if (!error)
> +		error = device_create_file(&cpu->dev,
> +					   &dev_attr_crash_notes_size);
>  #endif
>  	return error;
>  }

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