linux-kernel - Re: [PATCH v1 04/11] fs/proc/vmcore: move vmcore definitions from kcore.h to crash

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Message-ID: <Zz2u+2abswlwVcer@MiWiFi-R3L-srv>
Date: Wed, 20 Nov 2024 17:42:19 +0800
From: Baoquan He <bhe@...hat.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-s390@...r.kernel.org, virtualization@...ts.linux.dev,
	kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	kexec@...ts.infradead.org, Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>, Dave Young <dyoung@...hat.com>,
	Thomas Huth <thuth@...hat.com>, Cornelia Huck <cohuck@...hat.com>,
	Janosch Frank <frankja@...ux.ibm.com>,
	Claudio Imbrenda <imbrenda@...ux.ibm.com>,
	Eric Farman <farman@...ux.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v1 04/11] fs/proc/vmcore: move vmcore definitions from
 kcore.h to crash_dump.h

On 11/15/24 at 10:59am, David Hildenbrand wrote:
> On 15.11.24 10:44, Baoquan He wrote:
> > On 10/25/24 at 05:11pm, David Hildenbrand wrote:
> > > These defines are not related to /proc/kcore, move them to crash_dump.h
> > > instead. While at it, rename "struct vmcore" to "struct
> > > vmcore_mem_node", which is a more fitting name.
> > 
> > Agree it's inappropriate to put the defintions in kcore.h. However for
> > 'struct vmcore', it's only used in fs/proc/vmcore.c from my code
> > serching, do you think if we can put it in fs/proc/vmcore.c directly?
> > And 'struct vmcoredd_node' too.
> 
> See the next patches and how virtio-mem will make use of the feactored out
> functions. Not putting them as inline functions into a header will require
> exporting symbols just do add a vmcore memory node to the list, which I want
> to avoid -- overkill for these simple helpers.

I see. It makes sense to put them in crash_dump.h. Thanks for
explanation.

> 
> > 
> > And about the renaming, with my understanding each instance of struct
> > vmcore represents one memory region, isn't it a little confusing to be
> > called vmcore_mem_node? I understand you probablly want to unify the
> > vmcore and vmcoredd's naming. I have to admit I don't know vmcoredd well
> > and its naming, while most of people have been knowing vmcore representing
> > memory region very well.
> 
> I chose "vmcore_mem_node" because it is a memory range stored in a list.
> Note the symmetry with "vmcoredd_node"

I would say the justification of naming "vmcore_mem_node" is to keep
symmetry with "vmcoredd_node". If because it is a memory range, it really
should not be called vmcore_mem_node. As we know, memory node has
specific meaning in kernel, it's the memory range existing on a NUMA node.

And vmcoredd is not a widely used feature. At least in fedora/RHEL, we
leave it to customers themselves to use and handle, we don't support it.
And we add 'novmcoredd' to kdump kernel cmdline by default to disable it
in fedora/RHEL. So a rarely used feature should not be taken to decide
the naming of a mature and and widely used feature's name. My personal
opinion.

> 
> If there are strong feelings I can use a different name, but

Yes, I would suggest we better keep the old name or take a more
appropriate one if have to change.

> "vmcore_mem_node" really describes what it actually is. Especially now that
> we have different vmcore nodes.
> 
> -- 
> Cheers,
> 
> David / dhildenb
>