linux-kernel - Re: [PATCH 3/5] mm/madvise: thread VMA range state through madvise

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Message-ID: <7b08cd65-6797-4678-9c24-a3ffad7acb53@suse.cz>
Date: Fri, 20 Jun 2025 15:49:31 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>, Zi Yan <ziy@...dia.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>, Nico Pache
 <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
 Jann Horn <jannh@...gle.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Lance Yang <ioworker0@...il.com>,
 SeongJae Park <sj@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH 3/5] mm/madvise: thread VMA range state through
 madvise_behavior

On 6/19/25 22:26, Lorenzo Stoakes wrote:
> Rather than updating start and a confusing local parameter 'tmp' in
> madvise_walk_vmas(), instead store the current range being operated upon in
> the struct madvise_behavior helper object in a range pair and use this
> consistently in all operations.

Yeah much better but it still took me a bit to understand that "end" is now
the original range->end that doesn't change during the iterations. Maybe
make it const and comment?

> This makes it clearer what is going on and opens the door to further
> cleanup now we store state regarding what is currently being operated upon
> here.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/madvise.c | 101 ++++++++++++++++++++++++++++-----------------------
>  1 file changed, 55 insertions(+), 46 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 47485653c2a1..6faa38b92111 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -58,17 +58,26 @@ enum madvise_lock_mode {
>  	MADVISE_VMA_READ_LOCK,
>  };
>  
> +struct madvise_behavior_range {
> +	unsigned long start, end;

I also thought multiple names on one line is only done for local variables,
but always separate declarations in structs. But I don't know if it's
documented as such or if there are pre-existing counter examples. Consider
it a non-binding agreement with Zi :)

Thanks!