linux-kernel - Re: [PATCH v4 16/66] mm: Remove rb tree.

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Message-ID: <20220117011231.rkcdvkfqozdaexcg@revolver>
Date:   Mon, 17 Jan 2022 01:12:39 +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 16/66] mm: Remove rb tree.

* Vlastimil Babka <vbabka@...e.cz> [220112 07:03]:
> On 12/1/21 15:29, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > 
> > Remove the RB tree and start using the maple tree for vm_area_struct
> > tracking.
> > 
> > Drop validate_mm() calls in expand_upwards() and expand_downwards() as
> > the lock is not held.
> > 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> 
> > ---
> >  arch/x86/kernel/tboot.c    |   1 -
> >  drivers/firmware/efi/efi.c |   1 -
> >  include/linux/mm.h         |   2 -
> >  include/linux/mm_types.h   |  14 --
> >  kernel/fork.c              |   8 -
> >  mm/init-mm.c               |   2 -
> >  mm/mmap.c                  | 496 ++++++++-----------------------------
> >  mm/nommu.c                 |  88 ++-----
> >  mm/util.c                  |   8 +
> >  9 files changed, 136 insertions(+), 484 deletions(-)
> 
> Nice stats.

Thanks.

> 
> Wanted to suggest splitting out the swith to range_has_overlap() but I think
> I see how it's not feasible.
> 
> > diff --git a/mm/util.c b/mm/util.c
> > index e58151a61255..ab02382c2d57 100644
> > --- a/mm/util.c
> > +++ b/mm/util.c
> > @@ -287,6 +287,8 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
> >  	vma->vm_next = next;
> >  	if (next)
> >  		next->vm_prev = vma;
> > +	else
> > +		mm->highest_vm_end = vm_end_gap(vma);
> >  }
> >  
> >  void __vma_unlink_list(struct mm_struct *mm, struct vm_area_struct *vma)
> > @@ -301,6 +303,12 @@ void __vma_unlink_list(struct mm_struct *mm, struct vm_area_struct *vma)
> >  		mm->mmap = next;
> >  	if (next)
> >  		next->vm_prev = prev;
> > +	else {
> 
> Nit: style suggests that once else is { } block then if block should be too,
> even though it remains a single line.

Ack, I will fix this.  Although this function is completely dropped
later in the series.

> 
> > +		if (prev)
> > +			mm->highest_vm_end = vm_end_gap(prev);
> > +		else
> > +			mm->highest_vm_end = 0;
> > +	}
> >  }
> >  
> >  /* Check if the vma is being used as a stack by this task */
> 
>