linux-kernel - Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of walk_page

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Message-ID: <0abf8a75-24fb-4bce-8071-6ae654e62451@lucifer.local>
Date: Thu, 5 Jun 2025 15:20:40 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Barry Song <21cnbao@...il.com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        Barry Song <v-songbaohua@...o.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Jann Horn <jannh@...gle.com>, Suren Baghdasaryan <surenb@...gle.com>,
        Lokesh Gidra <lokeshgidra@...gle.com>, Dev Jain <dev.jain@....com>,
        Tangquan Zheng <zhengtangquan@...o.com>
Subject: Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of
 walk_page_range()

On Thu, Jun 05, 2025 at 04:12:48PM +0200, Vlastimil Babka wrote:
> On 6/5/25 10:31, Barry Song wrote:
> > From: Barry Song <v-songbaohua@...o.com>
> >
> > We've already found the VMA within madvise_walk_vmas() before calling
> > specific madvise behavior functions like madvise_free_single_vma().
> > So calling walk_page_range() and doing find_vma() again seems
> > unnecessary. It also prevents potential optimizations in those madvise
> > callbacks, particularly the use of dedicated per-VMA locking.
> >
> > Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> > Acked-by: David Hildenbrand <david@...hat.com>
> > Reviewed-by: Oscar Salvador <osalvador@...e.de>
> > Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > Cc: Vlastimil Babka <vbabka@...e.cz>
> > Cc: Jann Horn <jannh@...gle.com>
> > Cc: Suren Baghdasaryan <surenb@...gle.com>
> > Cc: Lokesh Gidra <lokeshgidra@...gle.com>
> > Cc: Dev Jain <dev.jain@....com>
> > Cc: Tangquan Zheng <zhengtangquan@...o.com>
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
>
> Thanks!
>
> > @@ -1160,7 +1160,7 @@ static long madvise_guard_install(struct vm_area_struct *vma,
> >  		unsigned long nr_pages = 0;
> >
> >  		/* Returns < 0 on error, == 0 if success, > 0 if zap needed. */
> > -		err = walk_page_range_mm(vma->vm_mm, start, end,
> > +		err = walk_page_range_vma(vma, start, end,
> >  					 &guard_install_walk_ops, &nr_pages);
>
> Nit: breaks the parameter alignment. Do we care? It's Lorenzo's code so
> maybe not ;P

OMG!!

Nah it's fine leave it as-is :P

Can always go fix it up at some later date... or make it more sane with just tab
alignment...

>
> >  		if (err < 0)
> >  			return err;
> > @@ -1244,7 +1244,7 @@ static long madvise_guard_remove(struct vm_area_struct *vma,
> >  	if (!is_valid_guard_vma(vma, /* allow_locked = */true))
> >  		return -EINVAL;
> >
> > -	return walk_page_range(vma->vm_mm, start, end,
> > +	return walk_page_range_vma(vma, start, end,
> >  			       &guard_remove_walk_ops, NULL);
>
> Same.
>
> >  }
> >
>