linux-kernel - Re: [PATCH RESEND] mm: hugetlb: simplify per-node sysfs creation and removal

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Date:   Fri, 19 Aug 2022 16:41:23 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        akpm@...ux-foundation.org, osalvador@...e.de, david@...hat.com,
        andi@...stfloor.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, muchun.song@...ux.dev
Subject: Re: [PATCH RESEND] mm: hugetlb: simplify per-node sysfs creation and
 removal

On 08/19/22 16:00, Muchun Song wrote:
> The following commit offload per-node sysfs creation and removal to a kworker and
> did not say why it is needed.  And it also said "I don't know that this is
> absolutely required".  It seems like the author was not sure as well.  Since it
> only complicates the code, this patch will revert the changes to simplify the code.
> 
>   39da08cb074c ("hugetlb: offload per node attribute registrations")
> 
> We could use memory hotplug notifier to do per-node sysfs creation and removal
> instead of inserting those operations to node registration and unregistration.
> Then, it can reduce the code coupling between node.c and hugetlb.c.  Also, it can
> simplify the code.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---

Looking at commit 39da08cb074c, it mentions that other memory register/unregister
handlers use work queues.  That seemed to be true at the time, but those handlers
have been rewritten or no longer exist.  With a quick look, I did not find any
memory notifiers doing so today.

I certainly like decoupling node driver and hugetlb code.  By no means am I an
expert in the hotplug interfaces.  I could not find any issues in moving the
functionality to memory hotplug notification.  FWICT, functionality should be

> 
> Cc Andi per Greg.
> 
>  drivers/base/node.c  | 139 ++-------------------------------------------------
>  include/linux/node.h |  24 ++-------
>  mm/hugetlb.c         |  45 +++++++++++------
>  3 files changed, 36 insertions(+), 172 deletions(-)

Acked-by: Mike Kravetz <mike.kravetz@...cle.com>
-- 
Mike Kravetz