linux-kernel - Re: [PATCH v2 1/2] kexec: Introduce "/sys/kernel/kexec_crash_low

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Date:   Tue, 23 Aug 2016 18:11:52 -0700
From:   Yinghai Lu <yinghai@...nel.org>
To:     Dave Young <dyoung@...hat.com>
Cc:     Xunlei Pang <xlpang@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Vivek Goyal <vgoyal@...hat.com>, Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH v2 1/2] kexec: Introduce "/sys/kernel/kexec_crash_low_size"

On Wed, Aug 17, 2016 at 1:20 AM, Dave Young <dyoung@...hat.com> wrote:
> On 08/17/16 at 09:50am, Xunlei Pang wrote:
>> "/sys/kernel/kexec_crash_size" only handles crashk_res, it
>> is fine in most cases, but sometimes we have crashk_low_res.
>> For example, when "crashkernel=size[KMG],high" combined with
>> "crashkernel=size[KMG],low" is used for 64-bit x86.
>>
>> Like crashk_res, we introduce the corresponding sysfs file
>> "/sys/kernel/kexec_crash_low_size" for crashk_low_res.
>>
>> So, the exact total reserved memory is the sum of the two.
>>
>> crashk_low_res can also be shrunk via this new interface,
>> and users should be aware of what they are doing.
...
>> @@ -218,6 +238,7 @@ static struct attribute * kernel_attrs[] = {
>>  #ifdef CONFIG_KEXEC_CORE
>>       &kexec_loaded_attr.attr,
>>       &kexec_crash_loaded_attr.attr,
>> +     &kexec_crash_low_size_attr.attr,
>>       &kexec_crash_size_attr.attr,
>>       &vmcoreinfo_attr.attr,
>>  #endif

would be better if you can use attribute_group .is_visible to control showing of
crash_low_size only when the crash_base is above 4G.

Thanks

Yinghai