linux-kernel - Re: [PATCH v3 12/16] mm/mmap: Clean up unmap

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Message-ID: <CAJuCfpHABTQoNXn4o0ZewLY7P+m2-BxO0b_87p21HeKrGqJ2xA@mail.gmail.com>
Date: Wed, 10 Jul 2024 10:14:42 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>, linux-mm@...ck.org, 
	Andrew Morton <akpm@...ux-foundation.org>, 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 12/16] mm/mmap: Clean up unmap_region() argument list

On Fri, Jul 5, 2024 at 1:33 PM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> On Thu, Jul 04, 2024 at 02:27:14PM GMT, Liam R. Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> >
> > With the only caller to unmap_region() being the error path of
> > mmap_region(), the argument list can be significantly reduced.
> >
> > There is also no need to forward declare the static function any
> > longer.
> >
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > ---
> >  mm/mmap.c | 25 +++++++++----------------
> >  1 file changed, 9 insertions(+), 16 deletions(-)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 45443a53be76..5d458c5f080e 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -76,11 +76,6 @@ int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
> >  static bool ignore_rlimit_data;
> >  core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
> >
> > -static void unmap_region(struct mm_struct *mm, struct ma_state *mas,
> > -             struct vm_area_struct *vma, struct vm_area_struct *prev,
> > -             struct vm_area_struct *next, unsigned long start,
> > -             unsigned long end, unsigned long tree_end, bool mm_wr_locked);
> > -
> >  static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
> >  {
> >       return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
> > @@ -2398,22 +2393,21 @@ struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
> >   *
> >   * Called with the mm semaphore held.
> >   */
> > -static void unmap_region(struct mm_struct *mm, struct ma_state *mas,
> > -             struct vm_area_struct *vma, struct vm_area_struct *prev,
> > -             struct vm_area_struct *next, unsigned long start,
> > -             unsigned long end, unsigned long tree_end, bool mm_wr_locked)
> > +static void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> > +             struct vm_area_struct *prev, struct vm_area_struct *next)
> >  {
> > +     struct mm_struct *mm = vma->vm_mm;
> >       struct mmu_gather tlb;
> > -     unsigned long mt_start = mas->index;
> >
> >       lru_add_drain();
> >       tlb_gather_mmu(&tlb, mm);
> >       update_hiwater_rss(mm);
> > -     unmap_vmas(&tlb, mas, vma, start, end, tree_end, mm_wr_locked);
> > -     mas_set(mas, mt_start);
>
> OK so the 'raise something in one patch only for it to be removed in the
> next' pattern continues :) more aesthetically plasing.
>
> > +     unmap_vmas(&tlb, mas, vma, vma->vm_start, vma->vm_end, vma->vm_end,
> > +                /* mm_wr_locked = */ true);
> > +     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,
> > -                              mm_wr_locked);
> > +                   next ? next->vm_start : USER_PGTABLES_CEILING,
> > +                   /* mm_wr_locked = */ true);
> >       tlb_finish_mmu(&tlb);
> >  }
> >
> > @@ -3186,8 +3180,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> >
> >               vma_iter_set(&vmi, vma->vm_end);
> >               /* Undo any partial mapping done by a device driver. */
> > -             unmap_region(mm, &vmi.mas, vma, prev, next, vma->vm_start,
> > -                          vma->vm_end, vma->vm_end, true);
> > +             unmap_region(&vmi.mas, vma, prev, next);
> >       }
> >       if (writable_file_mapping)
> >               mapping_unmap_writable(file->f_mapping);
> > --
> > 2.43.0
> >
>
> Lovely reduction in parameters.
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>