Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 5 Dec 2018 18:16:53 +0800
From:   Dave Young <dyoung@redhat.com>
To:     lijiang <lijiang@redhat.com>
Cc:     Borislav Petkov <bp@alien8.de>, linux-kernel@vger.kernel.org,
        kexec@lists.infradead.org, tglx@linutronix.de, mingo@redhat.com,
        x86@kernel.org, akpm@linux-foundation.org, bhe@redhat.com,
        Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org,
        Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Subject: Re: [PATCH 1/2 v2] kdump: add the vmcoreinfo documentation
Message-ID: <20181205101653.GA6940@dhcp-128-65.nay.redhat.com>
References: <20181202030839.29945-1-lijiang@redhat.com>
 <20181202030839.29945-2-lijiang@redhat.com>
 <20181203150809.GA4794@zn.tnic>
 <779dbae7-f6e2-e9e4-bdd0-0a9e6ec62487@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <779dbae7-f6e2-e9e4-bdd0-0a9e6ec62487@redhat.com>
User-Agent: Mutt/1.9.5 (2018-04-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> >> +init_uts_ns
> >> +===========
> >> +This is the UTS namespace, which is used to isolate two specific elements
> >> +of the system that relate to the uname system call. The UTS namespace is
> >> +named after the data structure used to store information returned by the
> >> +uname system call.
> > 
> > Those non-obvious exports should also have a short explanation why
> > they're part of VMCOREINFO.
> > 
> >> +
> >> +node_online_map
> >> +===============
> >> +It is a macro definition, actually it is an arrary node_states[N_ONLINE],
> >> +and it represents the set of online node in a system, one bit position
> >> +per node number.
> > 
> > Ditto.
> > 
> > So yeah, people can find out what those things are but I think it is
> > more important to state here *why* they're part of VMCOREINFO and how
> > they're used and why they're exported.
> > 
> 
> This is a good question.
> 
> For these two *why*, it should be easy to understand. Because user-space tools
> need to know basic information, such as the symbol values, field offset, structure
> size, etc. Otherwise, these tools won't know how to analyze the memory of the crash
> kernel.
> 
> For the second question 'how they are used', we can get the answer from user-space
> tools, such as makedumpfile, crash tools. Therefore, it may not need to explain any
> more in kernel document. On the other hand, if we must put these contents into kernel
> document, i have to say, that would be a hard task.

It should be a good chance to learn how makedumpfile works :),  Maybe it is
hard to get *all* of them, but it would be good to dig and find the
thing you can find then explain it.  And leave those *unknown* part as
FIXME or TODO, people can add description later. 

Added Kazu in cc as well..

Thanks
Dave