Re: [Xen-devel] [PATCH 1/9] mm: Introduce new vm_insert_range API

[Souptick Joarder <jrdr.linux@xxxxxxxxx>]

On Fri, Nov 16, 2018 at 11:59 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
>
> On Thu, Nov 15, 2018 at 09:15:30PM +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.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> > Reviewed-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > ---
> >  include/linux/mm_types.h |  3 +++
> >  mm/memory.c              | 28 ++++++++++++++++++++++++++++
> >  mm/nommu.c               |  7 +++++++
> >  3 files changed, 38 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);
> > +
> >  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..da904ed 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -1478,6 +1478,34 @@ 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: no. 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.
>
> Please add the return value and context descriptions.
>
> > + */
> > +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;
> > +}
> > +
> > +/**
> >   * 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.
>

Sure I will wait for some time to get additional review comments and
add all of those requested changes in v2.

Any further feedback on driver changes as part of this patch series ?

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