linux-kernel - Re: [PATCH v4 51/66] mm/khugepaged: Use maple tree iterators instead of vma linked list

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Date:   Tue, 25 Jan 2022 22:03:14 +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 51/66] mm/khugepaged: Use maple tree iterators instead
 of vma linked list

* Vlastimil Babka <vbabka@...e.cz> [220119 12:48]:
> On 12/1/21 15:30, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> Ah, got tired of copy/pasting for a number of patches, I see :)
> 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> >  mm/huge_memory.c | 4 ++--
> >  mm/khugepaged.c  | 9 ++++++---
> >  2 files changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index e5483347291c..f0f4ff5239ef 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2270,11 +2270,11 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma,
> >  	split_huge_pmd_if_needed(vma, end);
> >  
> >  	/*
> > -	 * If we're also updating the vma->vm_next->vm_start,
> > +	 * If we're also updating the vma_next(vma)->vm_start,
> 
> vma_next() takes an iterator, not vma, though.

I will fix this comment to be less code-specific since next isn't used
anyways.

> 
> >  	 * check if we need to split it.
> >  	 */
> >  	if (adjust_next > 0) {
> > -		struct vm_area_struct *next = vma->vm_next;
> > +		struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
> >  		unsigned long nstart = next->vm_start;
> >  		nstart += adjust_next;
> >  		split_huge_pmd_if_needed(next, nstart);
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 0ff7d72cdd1d..8f0633481791 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -2083,6 +2083,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> >  	struct mm_struct *mm;
> >  	struct vm_area_struct *vma;
> >  	int progress = 0;
> > +	unsigned long address;
> >  
> >  	VM_BUG_ON(!pages);
> >  	lockdep_assert_held(&khugepaged_mm_lock);
> > @@ -2106,11 +2107,13 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> >  	vma = NULL;
> >  	if (unlikely(!mmap_read_trylock(mm)))
> >  		goto breakouterloop_mmap_lock;
> > -	if (likely(!khugepaged_test_exit(mm)))
> > -		vma = find_vma(mm, khugepaged_scan.address);
> >  
> >  	progress++;
> > -	for (; vma; vma = vma->vm_next) {
> > +	if (unlikely(khugepaged_test_exit(mm)))
> > +		goto breakouterloop;
> > +
> > +	address = khugepaged_scan.address;
> > +	mt_for_each(&mm->mm_mt, vma, address, ULONG_MAX) {
> 
> Why not via mas_for_each()?

I will use for_each_vma() here.

> 
> >  		unsigned long hstart, hend;
> >  
> >  		cond_resched();
>