linux-kernel - Re: [PATCH v1 3/9] mm/vma: Add limits to unmap

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Message-ID: <keo5dm3fcn4upqdf2xt7epdkkgsryjgemaz4ng5r6sytkkpgon@gbnqq35blm7n>
Date: Tue, 13 Jan 2026 13:51:47 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, maple-tree@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...e.com>,
        Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
        Charan Teja Kalla <quic_charante@...cinc.com>,
        shikemeng@...weicloud.com, kasong@...cent.com, nphamcs@...il.com,
        bhe@...hat.com, baohua@...nel.org, chrisl@...nel.org,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v1 3/9] mm/vma: Add limits to unmap_region() for vmas

* Suren Baghdasaryan <surenb@...gle.com> [250909 16:10]:
> On Tue, Sep 9, 2025 at 12:10 PM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> >
> > Add a limit to the vma search instead of using the start and end of the
> > one passed in.
> 
> Would be good to explain why this is needed. I'm sure I'll find the
> answer in the later patches though.

I'll try to expand this comment to include why.

> 
> 
> >
> > No functional changes intended.
> >
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> 
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>
> 
> > ---
> >  mm/vma.c | 6 ++++--
> >  mm/vma.h | 1 +
> >  2 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/vma.c b/mm/vma.c
> > index abe0da33c8446..a648e0555c873 100644
> > --- a/mm/vma.c
> > +++ b/mm/vma.c
> > @@ -474,6 +474,7 @@ void remove_vma(struct vm_area_struct *vma)
> >   * Called with the mm semaphore held.
> >   */
> >  void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> > +               unsigned long vma_min, unsigned long vma_max,
> >                 struct vm_area_struct *prev, struct vm_area_struct *next)
> >  {
> >         struct mm_struct *mm = vma->vm_mm;
> > @@ -481,7 +482,7 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> >
> >         tlb_gather_mmu(&tlb, mm);
> >         update_hiwater_rss(mm);
> > -       unmap_vmas(&tlb, mas, vma, vma->vm_start, vma->vm_end, vma->vm_end,
> > +       unmap_vmas(&tlb, mas, vma, vma_min, vma_max, vma_max,
> >                    /* mm_wr_locked = */ true);
> >         mas_set(mas, vma->vm_end);
> >         free_pgtables(&tlb, mas, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
> > @@ -2417,7 +2418,8 @@ static int __mmap_new_file_vma(struct mmap_state *map,
> >
> >                 vma_iter_set(vmi, vma->vm_end);
> >                 /* Undo any partial mapping done by a device driver. */
> > -               unmap_region(&vmi->mas, vma, map->prev, map->next);
> > +               unmap_region(&vmi->mas, vma, vma->vm_start, vma->vm_end,
> > +                            map->prev, map->next);
> >
> >                 return error;
> >         }
> > diff --git a/mm/vma.h b/mm/vma.h
> > index 9183fe5490090..a9d0cef684ddb 100644
> > --- a/mm/vma.h
> > +++ b/mm/vma.h
> > @@ -261,6 +261,7 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
> >  void remove_vma(struct vm_area_struct *vma);
> >
> >  void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> > +               unsigned long min, unsigned long max,
> >                 struct vm_area_struct *prev, struct vm_area_struct *next);
> >
> >  /* We are about to modify the VMA's flags. */
> > --
> > 2.47.2
> >