linux-kernel - Re: [PATCH v6 10/20] mm/vma: Support vma == NULL in init_vma

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Message-ID: <kehvclm33n56d2bxugbpmwgqrtxsdzkfjnlzlknqnveqpl3ndm@6l2o5rjseb5b>
Date: Wed, 21 Aug 2024 09:18:38 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>, Vlastimil Babka <vbabka@...e.cz>,
        sidhartha.kumar@...cle.com, Bert Karwatzki <spasswolf@....de>,
        Jiri Olsa <olsajiri@...il.com>, Kees Cook <kees@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH v6 10/20] mm/vma: Support vma == NULL in init_vma_munmap()

* Lorenzo Stoakes <lorenzo.stoakes@...cle.com> [240821 06:07]:
> On Tue, Aug 20, 2024 at 07:57:19PM GMT, Liam R. Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> >
> > Adding support for a NULL vma means the init_vma_munmap() can be
> > initialized for a less error-prone process when calling
> > vms_complete_munmap_vmas() later on.
> >
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> 
> Thought I already R-b'd this :) Anyway,
> 
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

I probably lost it in my porting of patches somehow.  Thanks

> 
> > ---
> >  mm/mmap.c |  2 +-
> >  mm/vma.h  | 11 ++++++++---
> >  2 files changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index e7e6bf09b558..2b7445a002dc 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -1393,11 +1393,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> >
> >  	/* Find the first overlapping VMA */
> >  	vma = vma_find(&vmi, end);
> > +	init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
> >  	if (vma) {
> >  		mt_init_flags(&mt_detach, vmi.mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
> >  		mt_on_stack(mt_detach);
> >  		mas_init(&mas_detach, &mt_detach, /* addr = */ 0);
> > -		init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
> >  		/* Prepare to unmap any existing mapping in the area */
> >  		if (vms_gather_munmap_vmas(&vms, &mas_detach))
> >  			return -ENOMEM;
> > diff --git a/mm/vma.h b/mm/vma.h
> > index e78b24d1cf83..0e214bbf443e 100644
> > --- a/mm/vma.h
> > +++ b/mm/vma.h
> > @@ -95,9 +95,14 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms,
> >  {
> >  	vms->vmi = vmi;
> >  	vms->vma = vma;
> > -	vms->mm = vma->vm_mm;
> > -	vms->start = start;
> > -	vms->end = end;
> > +	if (vma) {
> > +		vms->mm = vma->vm_mm;
> > +		vms->start = start;
> > +		vms->end = end;
> > +	} else {
> > +		vms->mm = NULL;
> > +		vms->start = vms->end = 0;
> > +	}
> >  	vms->unlock = unlock;
> >  	vms->uf = uf;
> >  	vms->vma_count = 0;
> > --
> > 2.43.0
> >