linux-kernel - Re: [PATCH 1/2] include/linux/nodemask.h: create node

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Date:   Fri, 6 May 2022 12:23:48 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Peng Liu <liupeng256@...wei.com>
Cc:     bhelgaas@...gle.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
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        sudeep.holla@....com, rafael@...nel.org, lenb@...nel.org,
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        shinichiro.kawasaki@....com, mcgrof@...nel.org,
        jiangguoqing@...inos.cn, jpittman@...hat.com, dave@...olabs.net,
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Subject: Re: [PATCH 1/2] include/linux/nodemask.h: create node_available()
 helper

Subject line convention looks like "numa: ..."

On Fri, May 06, 2022 at 01:58:00AM +0000, Peng Liu wrote:
> Lots of code dose
               does

> 	node != NUMA_NO_NODE && !node_online(node)
> or
> 	node == NUMA_NO_NODE || node_online(node)
> so create node_available to do this to simplify code.
            node_available()

I'm not really sure what meaning "node_available" conveys, though.
Probably just because I don't understand NUMA.

Should the test for NUMA_NO_NODE be folded into node_state() or
node_online() directly instead of adding a new node_available()
interface?

NUMA_NO_NODE is -1.  It's not clear to me that node_state()/
node_isset()/test_bit() would do the right thing given -1.  I doubt
all node_online() callers ensure they don't pass NUMA_NO_NODE.

> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -70,6 +70,7 @@
>   *
>   * int node_online(node)		Is some node online?
>   * int node_possible(node)		Is some node possible?
> + * int node_available(node)		Is some node available(online or NUMA_NO_NODE)?

Existing file generally fits in 80 columns; follow that lead unless
you have a really good reason.  E.g., maybe this?

  + * int node_available(node)		Node online or NUMA_NO_NODE