linux-kernel - Re: [PATCH v7 12/21] mm/vma: Track start and end for munmap in vma_munmap

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Message-ID: <CAMuHMdW0HuK_26vejYL8nMwULwN8wFWS0-6HH69hOLuHzncwyA@mail.gmail.com>
Date: Mon, 26 Aug 2024 16:01:10 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.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 v7 12/21] mm/vma: Track start and end for munmap in vma_munmap_struct

Hi Liam,

On Thu, Aug 22, 2024 at 9:27 PM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>
> Set the start and end address for munmap when the prev and next are
> gathered.  This is needed to avoid incorrect addresses being used during
> the vms_complete_munmap_vmas() function if the prev/next vma are
> expanded.
>
> Add a new helper vms_complete_pte_clear(), which is needed later and
> will avoid growing the argument list to unmap_region() beyond the 9 it
> already has.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Thanks for your patch, which is now commit ca39aca8db2d78ff ("mm/vma:
track start and end for munmap in vma_munmap_struct") in next-20240826.

> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -38,6 +38,8 @@ struct vma_munmap_struct {
>         struct list_head *uf;           /* Userfaultfd list_head */
>         unsigned long start;            /* Aligned start addr (inclusive) */
>         unsigned long end;              /* Aligned end addr (exclusive) */
> +       unsigned long unmap_start;      /* Unmap PTE start */
> +       unsigned long unmap_end;        /* Unmap PTE end */
>         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 */
> @@ -108,6 +110,8 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms,
>         vms->vma_count = 0;
>         vms->nr_pages = vms->locked_vm = vms->nr_accounted = 0;
>         vms->exec_vm = vms->stack_vm = vms->data_vm = 0;
> +       vms->unmap_start = FIRST_USER_ADDRESS;
> +       vms->unmap_end = USER_PGTABLES_CEILING;

noreply@...erman.id.au reported build failures for m5272c3_defconfig
http://kisskb.ellerman.id.au/kisskb/buildresult/15224802/

$ make ARCH=m68k m5272c3_defconfig mm/filemap.o
In file included from mm/internal.h:22,
                 from mm/filemap.c:52:
mm/vma.h: In function ‘init_vma_munmap’:
mm/vma.h:113:21: error: ‘FIRST_USER_ADDRESS’ undeclared (first use in
this function)
  113 |  vms->unmap_start = FIRST_USER_ADDRESS;
      |                     ^~~~~~~~~~~~~~~~~~
mm/vma.h:113:21: note: each undeclared identifier is reported only
once for each function it appears in
mm/vma.h:114:19: error: ‘USER_PGTABLES_CEILING’ undeclared (first use
in this function)
  114 |  vms->unmap_end = USER_PGTABLES_CEILING;
      |                   ^~~~~~~~~~~~~~~~~~~~~

Both are defined in include/linux/pgtable.h inside #ifdef CONFIG_MMU,
so they are not available on nommu.


>  }
>
>  int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds