linux-kernel - Re: [PATCH v4 62/66] mm/swapfile: Use maple tree iterator instead of vma linked list

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Date:   Wed, 26 Jan 2022 17:08:47 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Vlastimil Babka <vbabka@...e.cz>
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>,
        Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 62/66] mm/swapfile: Use maple tree iterator instead of
 vma linked list

* Vlastimil Babka <vbabka@...e.cz> [220120 07:46]:
> On 12/1/21 15:30, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> 
> > ---
> >  mm/swapfile.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/mm/swapfile.c b/mm/swapfile.c
> > index e59e08ef46e1..21c88b0944f9 100644
> > --- a/mm/swapfile.c
> > +++ b/mm/swapfile.c
> > @@ -2103,15 +2103,18 @@ static int unuse_mm(struct mm_struct *mm, unsigned int type,
> >  {
> >  	struct vm_area_struct *vma;
> >  	int ret = 0;
> > +	MA_STATE(mas, &mm->mm_mt, 0, 0);
> >  
> >  	mmap_read_lock(mm);
> > -	for (vma = mm->mmap; vma; vma = vma->vm_next) {
> > +	mas_for_each(&mas, vma, ULONG_MAX) {
> >  		if (vma->anon_vma) {
> >  			ret = unuse_vma(vma, type, frontswap,
> >  					fs_pages_to_unuse);
> >  			if (ret)
> >  				break;
> >  		}
> > +
> > +		mas_pause(&mas);
> 
> AFAIU unnecessary for the resched as we don't drop anything and keep the
> mmap_lock?
> (and without that it could be VMA_ITERATOR?)

Agreed.  This was missed with the conversion of the locking.  Thanks.

> 
> >  		cond_resched();
> >  	}
> >  	mmap_read_unlock(mm);
>