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

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Message-ID: <af38005f-b726-4ff5-8d6d-a69175cc14cf@lucifer.local>
Date: Fri, 20 Jun 2025 14:51:24 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        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 Fri, Jun 20, 2025 at 03:49:31PM +0200, Vlastimil Babka wrote:
> 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>

Thanks!

>
> > ---
> >  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 :)

Hm I didn't realise that was a thing at struct level, and since Zi also
highlights this I'll change it :)

Sorry Zi - my confusion, I was thinking comma-separated wasn't just for locals.

>
> Thanks!