Re: [PATCH v2] mm: madvise: use walk_page_range_vma() instead of walk_page_range()

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

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@oppo.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@arm.com>
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> > Acked-by: David Hildenbrand <david@redhat.com>
> > Reviewed-by: Oscar Salvador <osalvador@suse.de>
> > Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
> > Cc: Vlastimil Babka <vbabka@suse.cz>
> > Cc: Jann Horn <jannh@google.com>
> > Cc: Suren Baghdasaryan <surenb@google.com>
> > Cc: Lokesh Gidra <lokeshgidra@google.com>
> > Cc: Dev Jain <dev.jain@arm.com>
> > Cc: Tangquan Zheng <zhengtangquan@oppo.com>
> > Signed-off-by: Barry Song <v-songbaohua@oppo.com>
>
> Reviewed-by: Vlastimil Babka <vbabka@suse.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.
>
> >  }
> >
>