linux-kernel - Re: [PATCH v10 10/69] mmap: use the VMA iterator in count_vma_pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220624131003.zydflhstzhx4clty@revolver>
Date:   Fri, 24 Jun 2022 13:10:10 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     David Hildenbrand <david@...hat.com>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "damon @ lists . linux . dev" <damon@...ts.linux.dev>,
        SeongJae Park <sj@...nel.org>
Subject: Re: [PATCH v10 10/69] mmap: use the VMA iterator in
 count_vma_pages_range()

* David Hildenbrand <david@...hat.com> [220621 17:13]:
> On 21.06.22 22:46, Liam Howlett wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> > 
> > This simplifies the implementation and is faster than using the linked
> > list.
> > 
> > Link: https://lkml.kernel.org/r/20220504010716.661115-12-Liam.Howlett@oracle.com
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > Acked-by: Vlastimil Babka <vbabka@...e.cz>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: David Howells <dhowells@...hat.com>
> > Cc: SeongJae Park <sj@...nel.org>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Davidlohr Bueso <dave@...olabs.net>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> > ---
> >  mm/mmap.c | 24 +++++++-----------------
> >  1 file changed, 7 insertions(+), 17 deletions(-)
> > 
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 6be7833c781b..d7e6baa2f40f 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -675,29 +675,19 @@ munmap_vma_range(struct mm_struct *mm, unsigned long start, unsigned long len,
> >  
> >  	return 0;
> >  }
> > +
> >  static unsigned long count_vma_pages_range(struct mm_struct *mm,
> >  		unsigned long addr, unsigned long end)
> >  {
> > -	unsigned long nr_pages = 0;
> > +	VMA_ITERATOR(vmi, mm, addr);
> >  	struct vm_area_struct *vma;
> > +	unsigned long nr_pages = 0;
> >  
> > -	/* Find first overlapping mapping */
> > -	vma = find_vma_intersection(mm, addr, end);
> > -	if (!vma)
> > -		return 0;
> > -
> > -	nr_pages = (min(end, vma->vm_end) -
> > -		max(addr, vma->vm_start)) >> PAGE_SHIFT;
> > -
> > -	/* Iterate over the rest of the overlaps */
> > -	for (vma = vma->vm_next; vma; vma = vma->vm_next) {
> > -		unsigned long overlap_len;
> > -
> > -		if (vma->vm_start > end)
> > -			break;
> > +	for_each_vma_range(vmi, vma, end) {
> > +		unsigned long vm_start = max(addr, vma->vm_start);
> > +		unsigned long vm_end = min(end, vma->vm_end);
> 
> I thought using max_t and min_t was the latest advisory. I might be
> wrong and simply kept doing it that way ;)

They are the same type so I think this is okay.

> 
> >  
> > -		overlap_len = min(end, vma->vm_end) - vma->vm_start;
> > -		nr_pages += overlap_len >> PAGE_SHIFT;
> > +		nr_pages += (vm_end - vm_start) / PAGE_SIZE;
> 
> PHYS_PFN(vm_end - vm_start)
> 
> >  	}
> >  
> >  	return nr_pages;
> 
> Reviewed-by: David Hildenbrand <david@...hat.com>
> 
> -- 
> Thanks,
> 
> David / dhildenb
>