Re: [PATCH v2 1/9] mm: Introduce new vm_insert_range API

[Souptick Joarder <jrdr.linux@gmail.com>]

Hi Mike,

On Sun, Dec 2, 2018 at 4:43 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
>
> On Sun, Dec 02, 2018 at 11:49:44AM +0530, Souptick Joarder wrote:
> > Previouly drivers have their own way of mapping range of
> > kernel pages/memory into user vma and this was done by
> > invoking vm_insert_page() within a loop.
> >
> > As this pattern is common across different drivers, it can
> > be generalized by creating a new function and use it across
> > the drivers.
> >
> > vm_insert_range is the new API which will be used to map a
> > range of kernel memory/pages to user vma.
> >
> > This API is tested by Heiko for Rockchip drm driver, on rk3188,
> > rk3288, rk3328 and rk3399 with graphics.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> > Reviewed-by: Matthew Wilcox <willy@infradead.org>
> > Tested-by: Heiko Stuebner <heiko@sntech.de>
> > ---
> >  include/linux/mm_types.h |  3 +++
> >  mm/memory.c              | 38 ++++++++++++++++++++++++++++++++++++++
> >  mm/nommu.c               |  7 +++++++
> >  3 files changed, 48 insertions(+)
> >
> > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > index 5ed8f62..15ae24f 100644
> > --- a/include/linux/mm_types.h
> > +++ b/include/linux/mm_types.h
> > @@ -523,6 +523,9 @@ extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
> >  extern void tlb_finish_mmu(struct mmu_gather *tlb,
> >                               unsigned long start, unsigned long end);
> >
> > +int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
> > +                     struct page **pages, unsigned long page_count);
> > +
>
> This seem to belong to include/linux/mm.h, near vm_insert_page()

Ok, I will change it. Apart from this change does it looks good ?

>
> >  static inline void init_tlb_flush_pending(struct mm_struct *mm)
> >  {
> >       atomic_set(&mm->tlb_flush_pending, 0);
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 15c417e..84ea46c 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -1478,6 +1478,44 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> >  }
> >
> >  /**
> > + * vm_insert_range - insert range of kernel pages into user vma
> > + * @vma: user vma to map to
> > + * @addr: target user address of this page
> > + * @pages: pointer to array of source kernel pages
> > + * @page_count: number of pages need to insert into user vma
> > + *
> > + * This allows drivers to insert range of kernel pages they've allocated
> > + * into a user vma. This is a generic function which drivers can use
> > + * rather than using their own way of mapping range of kernel pages into
> > + * user vma.
> > + *
> > + * If we fail to insert any page into the vma, the function will return
> > + * immediately leaving any previously-inserted pages present.  Callers
> > + * from the mmap handler may immediately return the error as their caller
> > + * will destroy the vma, removing any successfully-inserted pages. Other
> > + * callers should make their own arrangements for calling unmap_region().
> > + *
> > + * Context: Process context. Called by mmap handlers.
> > + * Return: 0 on success and error code otherwise
> > + */
> > +int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
> > +                     struct page **pages, unsigned long page_count)
> > +{
> > +     unsigned long uaddr = addr;
> > +     int ret = 0, i;
> > +
> > +     for (i = 0; i < page_count; i++) {
> > +             ret = vm_insert_page(vma, uaddr, pages[i]);
> > +             if (ret < 0)
> > +                     return ret;
> > +             uaddr += PAGE_SIZE;
> > +     }
> > +
> > +     return ret;
> > +}
> > +EXPORT_SYMBOL(vm_insert_range);
> > +
> > +/**
> >   * vm_insert_page - insert single page into user vma
> >   * @vma: user vma to map to
> >   * @addr: target user address of this page
> > diff --git a/mm/nommu.c b/mm/nommu.c
> > index 749276b..d6ef5c7 100644
> > --- a/mm/nommu.c
> > +++ b/mm/nommu.c
> > @@ -473,6 +473,13 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
> >  }
> >  EXPORT_SYMBOL(vm_insert_page);
> >
> > +int vm_insert_range(struct vm_area_struct *vma, unsigned long addr,
> > +                     struct page **pages, unsigned long page_count)
> > +{
> > +     return -EINVAL;
> > +}
> > +EXPORT_SYMBOL(vm_insert_range);
> > +
> >  /*
> >   *  sys_brk() for the most part doesn't need the global kernel
> >   *  lock, except when an application is doing something nasty
> > --
> > 1.9.1
> >
>
> --
> Sincerely yours,
> Mike.
>