linux-kernel - Re: retiring laptop_mode? was Re: [PATCH] mm: vmscan: always allow writeback during memcg reclaim

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Message-ID: <aUMLmJ0En24pQBX_@cmpxchg.org>
Date: Wed, 17 Dec 2025 14:59:20 -0500
From: Johannes Weiner <hannes@...xchg.org>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Christoph Hellwig <hch@...radead.org>, Jens Axboe <axboe@...nel.dk>,
	Deepanshu Kartikey <kartikey406@...il.com>,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: retiring laptop_mode? was Re: [PATCH] mm: vmscan: always allow
 writeback during memcg reclaim

On Tue, Dec 16, 2025 at 03:23:53PM -0800, Shakeel Butt wrote:
> On Tue, Dec 16, 2025 at 01:52:01PM -0500, Johannes Weiner wrote:

> Reviewed-by: Shakeel Butt <shakeel.butt@...ux.dev>

Thanks!

> > --- a/include/uapi/linux/sysctl.h
> > +++ b/include/uapi/linux/sysctl.h
> > @@ -183,7 +183,7 @@ enum
> >  	VM_LOWMEM_RESERVE_RATIO=20,/* reservation ratio for lower memory zones */
> >  	VM_MIN_FREE_KBYTES=21,	/* Minimum free kilobytes to maintain */
> >  	VM_MAX_MAP_COUNT=22,	/* int: Maximum number of mmaps/address-space */
> > -	VM_LAPTOP_MODE=23,	/* vm laptop mode */
> > +
> 
> There are 8 earlier enums here with names like VM_UNUSED* along with
> the information on what were they. Should we have something similar for
> this one? Something like:
> 
> 	VM_UNUSED10=23, /* was vm laptop mode */

The other enums in that file leave holes, the VM ones have a mix of
VM_UNUSED and holes. I don't think it matters either way since the
sysctl syscall has been removed and nothing new should be compiled
against the definitions in this file, right?