linux-kernel - Re: [PATCH v4 06/66] mm: Start tracking VMAs with maple tree

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Message-ID: <20211208181121.us2sxqjaiamol7yf@revolver>
Date:   Wed, 8 Dec 2021 18:11:29 +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 06/66] mm: Start tracking VMAs with maple tree

* Vlastimil Babka <vbabka@...e.cz> [211207 13:01]:
> On 12/1/21 15:29, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > 
> > Start tracking the VMAs with the new maple tree structure in parallel
> > with the rb_tree.  Add debug and trace events for maple tree operations
> > and duplicate the rb_tree that is created on forks into the maple tree.
> > 
> > The maple tree is added to the mm_struct including the mm_init struct,
> > added support in required mm/mmap functions, added tracking in
> > kernel/fork for process forking, and used to find the unmapped_area and
> > checked against what the rbtree finds.
> > 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> > ---
> >  arch/x86/kernel/tboot.c     |   1 +
> >  drivers/firmware/efi/efi.c  |   1 +
> >  include/linux/mm.h          |   2 +
> >  include/linux/mm_types.h    |   3 +
> >  include/trace/events/mmap.h |  71 ++++++++++++
> >  init/main.c                 |   2 +
> >  kernel/fork.c               |   5 +
> >  mm/init-mm.c                |   2 +
> >  mm/internal.h               |  73 ++++++++++++
> >  mm/mmap.c                   | 220 +++++++++++++++++++++++++++++++++++-
> >  10 files changed, 378 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
> > index f9af561c3cd4..859e8d2ea070 100644
> > --- a/arch/x86/kernel/tboot.c
> > +++ b/arch/x86/kernel/tboot.c
> > @@ -98,6 +98,7 @@ void __init tboot_probe(void)
> >  static pgd_t *tboot_pg_dir;
> >  static struct mm_struct tboot_mm = {
> >  	.mm_rb          = RB_ROOT,
> > +	.mm_mt          = MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, tboot_mm.mmap_lock),
> >  	.pgd            = swapper_pg_dir,
> >  	.mm_users       = ATOMIC_INIT(2),
> >  	.mm_count       = ATOMIC_INIT(1),
> > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > index ae79c3300129..0b40291416ca 100644
> > --- a/drivers/firmware/efi/efi.c
> > +++ b/drivers/firmware/efi/efi.c
> > @@ -55,6 +55,7 @@ static unsigned long __initdata rt_prop = EFI_INVALID_TABLE_ADDR;
> >  
> >  struct mm_struct efi_mm = {
> >  	.mm_rb			= RB_ROOT,
> > +	.mm_mt			= MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, efi_mm.mmap_lock),
> >  	.mm_users		= ATOMIC_INIT(2),
> >  	.mm_count		= ATOMIC_INIT(1),
> >  	.write_protect_seq      = SEQCNT_ZERO(efi_mm.write_protect_seq),
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index a7e4a9e7d807..9eae78a155be 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2610,6 +2610,8 @@ extern bool arch_has_descending_max_zone_pfns(void);
> >  /* nommu.c */
> >  extern atomic_long_t mmap_pages_allocated;
> >  extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t);
> > +/* maple_tree */
> 
> Hm should it say mmap.c as that's where vma_store() is defined.
> 
> ...

Yes, I will change that.

> 
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index bfb0ea164a90..c2f1431886d4 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> 
> ...
> 
> > @@ -1901,12 +2018,21 @@ static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
> >  	struct mm_struct *mm = current->mm;
> >  	struct vm_area_struct *vma;
> >  	unsigned long length, low_limit, high_limit, gap_start, gap_end;
> > +	unsigned long gap;
> > +	MA_STATE(mas, &mm->mm_mt, 0, 0);
> >  
> >  	/* Adjust search length to account for worst case alignment overhead */
> >  	length = info->length + info->align_mask;
> >  	if (length < info->length)
> >  		return -ENOMEM;
> >  
> > +	rcu_read_lock();
> > +	mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
> > +			   length);
> 
> unmapped_area_topdown also uses mas_empty_area_rev(), shouldn't this one be
> non-rev()?

Yes, good catch. I changed this in a later patch to the correct function, but this needs to be fixed.

> 
> > +	rcu_read_unlock();
> > +	gap = mas.index;
> > +	gap += (info->align_offset - gap) & info->align_mask;
> > +
> >  	/* Adjust search limits by the desired length */
> >  	if (info->high_limit < length)
> >  		return -ENOMEM;
> > @@ -1988,20 +2114,39 @@ static unsigned long unmapped_area(struct vm_unmapped_area_info *info)
> >  
> >  	VM_BUG_ON(gap_start + info->length > info->high_limit);
> >  	VM_BUG_ON(gap_start + info->length > gap_end);
> > +
> > +	VM_BUG_ON(gap != gap_start);
> >  	return gap_start;
> >  }
> >  
> > +static inline unsigned long top_area_aligned(struct vm_unmapped_area_info *info,
> > +					     unsigned long end)
> > +{
> > +	return (end - info->length - info->align_offset) & (~info->align_mask);
> > +}
> 
> Looks like this is never used anywhere and just deleted later in the series.

Yes, this was from a conflict in the mmotm branch a while back.  I will
remove it.

> 
> > +
> >  static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
> >  {
> >  	struct mm_struct *mm = current->mm;
> > -	struct vm_area_struct *vma;
> > +	struct vm_area_struct *vma = NULL;
> >  	unsigned long length, low_limit, high_limit, gap_start, gap_end;
> > +	unsigned long gap;
> > +
> > +	MA_STATE(mas, &mm->mm_mt, 0, 0);
> > +	validate_mm_mt(mm);
> >  
> >  	/* Adjust search length to account for worst case alignment overhead */
> >  	length = info->length + info->align_mask;
> >  	if (length < info->length)
> >  		return -ENOMEM;
> >  
> > +	rcu_read_lock();
> > +	mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
> > +		   length);
> > +	rcu_read_unlock();
> > +	gap = (mas.index + info->align_mask) & ~info->align_mask;
> > +	gap -= info->align_offset & info->align_mask;
> > +
> >  	/*
> >  	 * Adjust search limits by the desired length.
> >  	 * See implementation comment at top of unmapped_area().