linux-kernel - Re: [PATCH v1 5/9] mm/vma: Add page table limit to unmap

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Message-ID: <qoa4jbke3gd3q6u2dyt2cgvkoxfibxlo4t5vvck4j2efddbdh4@agowka7u6qqa>
Date: Tue, 13 Jan 2026 15:09:11 -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 5/9] mm/vma: Add page table limit to unmap_region()

* Suren Baghdasaryan <surenb@...gle.com> [250909 17:29]:
> On Tue, Sep 9, 2025 at 12:10 PM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> >
> > The unmap_region() calls need to pass through the page table limit for a
> > future patch.
> >
> > No functional changes intended.
> >
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> >  mm/vma.c | 5 +++--
> >  mm/vma.h | 2 +-
> >  2 files changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/vma.c b/mm/vma.c
> > index 1bae142bbc0f1..4c850ffd83a4b 100644
> > --- a/mm/vma.c
> > +++ b/mm/vma.c
> > @@ -474,7 +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,
> > +               unsigned long vma_min, unsigned long vma_max, unsigned long pg_max,
> >                 struct vm_area_struct *prev, struct vm_area_struct *next)
> >  {
> >         struct mm_struct *mm = vma->vm_mm;
> > @@ -487,7 +487,7 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> >         mas_set(mas, vma->vm_end);
> >         free_pgtables(&tlb, mas, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
> >                       next ? next->vm_start : USER_PGTABLES_CEILING,
> > -                     next ? next->vm_start : USER_PGTABLES_CEILING,
> > +                     pg_max,
> 
> Hmm. The free_pgtables() parameters were advertised as:
> 
> @floor: The lowest page table address
> @ceiling: The highest page table address
> @tree_max: The highest tree search address
> 
> but here tree_max=pg_max. I would expect pg_max to mean "The highest
> page table address", IOW we should have ceiling=pg_max. Either the
> order of the parameters is wrong here or the names are misleading.

Ah, the order is incorrect.  Thanks.

> I also think in the previous patch we should have renamed
> free_pgtables() parameters to vma_min, vma_max and pg_max like here
> for consistency and to avoid confusion.

vma_min turns int the page table floor, so that one doesn't work.  If I
update one and not the others, it gets a bit odd.

These also all go away, so we'll have internal series renaming.

> 
> >                       /* mm_wr_locked = */ true);
> >         tlb_finish_mmu(&tlb);
> >  }
> > @@ -2420,6 +2420,7 @@ 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, vma->vm_start, vma->vm_end,
> > +                            map->next ? map->next->vm_start : USER_PGTABLES_CEILING,
> >                              map->prev, map->next);
> >
> >                 return error;
> > diff --git a/mm/vma.h b/mm/vma.h
> > index a9d0cef684ddb..b0ebc81d5862e 100644
> > --- a/mm/vma.h
> > +++ b/mm/vma.h
> > @@ -261,7 +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,
> > +               unsigned long min, unsigned long max, unsigned long pg_max,
> >                 struct vm_area_struct *prev, struct vm_area_struct *next);
> >
> >  /* We are about to modify the VMA's flags. */
> > --
> > 2.47.2
> >