linux-kernel - Re: [PATCH v3 05/16] mm/mmap: Introduce vma_munmap

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Message-ID: <CAJuCfpG+Jok-ySXzRkokU-hrvnLxxMkeufXRMk1tmPLQcgnzNw@mail.gmail.com>
Date: Wed, 10 Jul 2024 09:07:23 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Suren Baghdasaryan <surenb@...gle.com>, Vlastimil Babka <vbabka@...e.cz>, Lorenzo Stoakes <lstoakes@...il.com>, 
	Matthew Wilcox <willy@...radead.org>, sidhartha.kumar@...cle.com, 
	"Paul E . McKenney" <paulmck@...nel.org>, Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>, 
	linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 05/16] mm/mmap: Introduce vma_munmap_struct for use in
 munmap operations

On Fri, Jul 5, 2024 at 12:09 PM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
>
> * Lorenzo Stoakes <lorenzo.stoakes@...cle.com> [240705 14:39]:
> > On Thu, Jul 04, 2024 at 02:27:07PM GMT, Liam R. Howlett wrote:
> > > Use a structure to pass along all the necessary information and counters
> > > involved in removing vmas from the mm_struct.
> > >
> > > Update vmi_ function names to vms_ to indicate the first argument
> > > type change.
> > >
> > > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > > Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>
> > > ---
> > >  mm/internal.h |  16 ++++++
> > >  mm/mmap.c     | 137 ++++++++++++++++++++++++++------------------------
> > >  2 files changed, 88 insertions(+), 65 deletions(-)
> > >
> > > diff --git a/mm/internal.h b/mm/internal.h
> > > index 2ea9a88dcb95..f1e6dea2efcf 100644
> > > --- a/mm/internal.h
> > > +++ b/mm/internal.h
> > > @@ -1481,6 +1481,22 @@ struct vma_prepare {
> > >     struct vm_area_struct *remove2;
> > >  };
> > >
> > > +/*
> > > + * vma munmap operation
> > > + */
> > > +struct vma_munmap_struct {
> > > +   struct vma_iterator *vmi;
> > > +   struct mm_struct *mm;
> > > +   struct vm_area_struct *vma;     /* The first vma to munmap */
> > > +   struct list_head *uf;           /* Userfaultfd list_head */
> > > +   unsigned long start;            /* Aligned start addr */
> > > +   unsigned long end;              /* Aligned end addr */
> > > +   int vma_count;                  /* Number of vmas that will be removed */
> > > +   unsigned long nr_pages;         /* Number of pages being removed */
> > > +   unsigned long locked_vm;        /* Number of locked pages */
> > > +   bool unlock;                    /* Unlock after the munmap */
> > > +};
> >
> >
> > I'm a big fan of breaking out and threading state like this through some of
> > these more... verbose VMA functions.
> >
> > I have a similar idea as part of my long dreamed of 'delete vma_merge()'
> > patch set. Coming soon :)
> >
> > > +
> > >  void __meminit __init_single_page(struct page *page, unsigned long pfn,
> > >                             unsigned long zone, int nid);
> > >
> > > diff --git a/mm/mmap.c b/mm/mmap.c
> > > index 8dc8ffbf9d8d..76e93146ee9d 100644
> > > --- a/mm/mmap.c
> > > +++ b/mm/mmap.c
> > > @@ -500,6 +500,31 @@ static inline void init_vma_prep(struct vma_prepare *vp,
> > >     init_multi_vma_prep(vp, vma, NULL, NULL, NULL);
> > >  }
> > >
> > > +/*
> > > + * init_vma_munmap() - Initializer wrapper for vma_munmap_struct
> > > + * @vms: The vma munmap struct
> > > + * @vmi: The vma iterator
> > > + * @vma: The first vm_area_struct to munmap
> > > + * @start: The aligned start address to munmap
> > > + * @end: The aligned end address to munmap
> >
> > Maybe worth mentioning if inclusive/exclusive.
>
> The "address to munmap" isn't specific enough that we are using the same
> logic as the munmap call?  That is, the vma inclusive and exclusive for
> start and end, respectively.
>
> Not a big change, either way.

+1. Every time I look into these functions with start/end I have to go
back and check these inclusive/exclusive rules, so mentioning it would
be helpful.


>
> ...
>
> >
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
>
> Thanks
>